Wine Developer's Guide
     __________________________________________________________

   Table of Contents
   I. Developing Wine

        Debugging Wine

              Introduction
              WineDbg's modes of invocation
              Using the Wine Debugger
              Useful memory addresses
              Configuration
              WineDbg Expressions and Variables
              WineDbg Command Reference
              Other debuggers

        Debug Logging

              Debugging classes
              Debugging channels
              Are we debugging?
              Helper functions
              Controlling the debugging output
              Compiling Out Debugging Messages
              A Few Notes on Style

        Other debugging techniques

              Understanding undocumented APIs
              How to do regression testing using Git
              Which code has been tested?

        Coding Practice

              Patch Format
              Some notes about style
              Quality Assurance
              Porting Wine to new Platforms
              Adding New Languages

        Writing Conformance tests

              Introduction
              What to test for?
              Running the tests in Wine
              Cross-compiling the tests with MinGW
              Building and running the tests on Windows
              Inside a test
              Writing good error messages
              Handling platform issues

        Documenting Wine

              An Overview Of Wine Documentation
              Writing Wine API Documentation
              The Wine DocBook System

   II. Wine Architecture

        Overview

              Wine Overview
              Standard Windows Architectures
              Wine architecture

        Kernel modules

              The Wine initialization process
              Detailed memory management
              Multi-processing in Wine
              Multi-threading in Wine
              Structured Exception Handling
              File management
              NTDLL module
              KERNEL32 Module

        Graphical modules

              GDI Module

        Windowing system

              USER Module
              X Windows System interface

        COM in Wine

              Writing COM Components for Wine
              A brief introduction to DCOM in Wine

        Wine and OpenGL

              What is needed to have OpenGL support in Wine
              How it all works
              Known problems

        Outline of DirectDraw Architecture

              DirectDraw inheritance tree
              DirectDrawSurface inheritance tree
              Interface Thunks
              Logical Object Layout
              Creating Objects

        Wine and Multimedia

              Overview
              Multimedia architecture
              Low level layers
              Mid level drivers (MCI)
              High level layers
              MS ACM Dlls
              MS Video Dlls
              Multimedia configuration

I. Developing Wine

   Table of Contents
   Debugging Wine
   Debug Logging
   Other debugging techniques
   Coding Practice
   Writing Conformance tests
   Documenting Wine
     __________________________________________________________

Debugging Wine

Introduction

Processes and threads: in underlying OS and in Windows

   Before going into the depths of debugging in Wine, here's a
   small overview of process and thread handling in Wine. It has
   to be clear that there are two different beasts:
   processes/threads from the Unix point of view and
   processes/threads from a Windows point of view.

   Each Windows' thread is implemented as a Unix thread, meaning
   that all threads of a same Windows' process share the same
   (unix) address space.

   In the following:

     * W-process means a process in Windows' terminology
     * U-process means a process in Unix' terminology
     * W-thread means a thread in Windows' terminology

   A W-process is made of one or several W-threads. Each W-thread
   is mapped to one and only one U-process. All U-processes of a
   same W-process share the same address space.

   Each Unix process can be identified by two values:

     * the Unix process id (upid in the following)
     * the Windows's thread id (tid)

   Each Windows' process has also a Windows' process id (wpid in
   the following). It must be clear that upid and wpid are
   different and shall not be used instead of the other.

   Wpid and tid are defined (Windows) system wide. They must not
   be confused with process or thread handles which, as any
   handle, is an indirection to a system object (in this case
   process or thread). A same process can have several different
   handles on the same kernel object. The handles can be defined
   as local (the values is only valid in a process), or system
   wide (the same handle can be used by any W-process).
     __________________________________________________________

Wine, debugging and WineDbg

   When talking of debugging in Wine, there are at least two
   levels to think of:

     * the Windows' debugging API.
     * the Wine integrated debugger, dubbed winedbg.

   Wine implements most of the Windows' debugging API. The first
   part of the debugging APIs (in KERNEL32.DLL) allows a
   W-process, called the debugger, to control the execution of
   another W-process, the debuggee. To control means
   stopping/resuming execution, enabling/disabling single
   stepping, setting breakpoints, reading/writing debuggee
   memory... Another part of the debugging APIs resides in
   DBGHELP.DLL (and its ancestor IMAGEHLP.DLL) and lets a debugger
   look into symbols and types from any module (if the module has
   been compiled with the proper options).

   winedbg is a Winelib application making use of these APIs
   (KERNEL32.DLL's debugging API and DBGHELP.DLL) to allow
   debugging both any Wine or Winelib applications as well as Wine
   itself (kernel and all DLLs).
     __________________________________________________________

WineDbg's modes of invocation

Starting a process

   Any application (either a Windows' native executable, or a
   Winelib application) can be run through winedbg. Command line
   options and tricks are the same as for wine:
winedbg telnet.exe
winedbg hl.exe -windowed
     __________________________________________________________

Attaching

   winedbg can also be launched without any command line argument:
   winedbg is started without any attached process. You can get a
   list of running W-processes (and their wpid's) using the info
   process command, and then, with the attach command, pick up the
   wpid of the W-process you want to debug. This is a neat feature
   as it allows you to debug an already started application.
     __________________________________________________________

On exceptions

   When something goes wrong, Windows tracks this as an exception.
   Exceptions exist for segmentation violation, stack overflow,
   division by zero, etc.

   When an exception occurs, Wine checks if the W-process is
   debugged. If so, the exception event is sent to the debugger,
   which takes care of it: end of the story. This mechanism is
   part of the standard Windows' debugging API.

   If the W-process is not debugged, Wine tries to launch a
   debugger. This debugger (normally winedbg, see III
   Configuration for more details), at startup, attaches to the
   W-process which generated the exception event. In this case,
   you are able to look at the causes of the exception, and either
   fix the causes (and continue further the execution) or dig
   deeper to understand what went wrong.

   If winedbg is the standard debugger, the pass and cont commands
   are the two ways to let the process go further for the handling
   of the exception event.

   To be more precise on the way Wine (and Windows) generates
   exception events, when a fault occurs (segmentation violation,
   stack overflow...), the event is first sent to the debugger
   (this is known as a first chance exception). The debugger can
   give two answers:

   continue
          the debugger had the ability to correct what's generated
          the exception, and is now able to continue process
          execution.

   pass
          the debugger couldn't correct the cause of the first
          chance exception. Wine will now try to walk the list of
          exception handlers to see if one of them can handle the
          exception. If no exception handler is found, the
          exception is sent once again to the debugger to indicate
          the failure of the exception handling.

   Note

   since some of Wine's code uses exceptions and try/catch blocks
   to provide some functionality, winedbg can be entered in such
   cases with segv exceptions. This happens, for example, with
   IsBadReadPtr function. In that case, the pass command shall be
   used, to let the handling of the exception to be done by the
   catch block in IsBadReadPtr.
     __________________________________________________________

Interrupting

   You can stop the debugger while it's running by hitting Ctrl-C
   in its window. This will stop the debugged process, and let you
   manipulate the current context.
     __________________________________________________________

Quitting

   Wine supports the new XP APIs, allowing for a debugger to
   detach from a program being debugged (see detach command).
     __________________________________________________________

Using the Wine Debugger

   This section describes where to start debugging Wine. If at any
   point you get stuck and want to ask for help, please read the
   How to Report A Bug section of the Wine Users Guide for
   information on how to write useful bug reports.
     __________________________________________________________

Crashes

   These usually show up like this:
|Unexpected Windows program segfault - opcode = 8b
|Segmentation fault in Windows program 1b7:c41.
|Loading symbols from ELF file /root/wine/wine...
|....more Loading symbols from ...
|In 16 bit mode.
|Register dump:
| CS:01b7 SS:016f DS:0287 ES:0000
| IP:0c41 SP:878a BP:8796 FLAGS:0246
| AX:811e BX:0000 CX:0000 DX:0000 SI:0001 DI:ffff
|Stack dump:
|0x016f:0x878a:  0001 016f ffed 0000 0000 0287 890b 1e5b
|0x016f:0x879a:  01b7 0001 000d 1050 08b7 016f 0001 000d
|0x016f:0x87aa:  000a 0003 0004 0000 0007 0007 0190 0000
|0x016f:0x87ba:
|
|0050: sel=0287 base=40211d30 limit=0b93f (bytes) 16-bit rw-
|Backtrace:
|0 0x01b7:0x0c41 (PXSRV_FONGETFACENAME+0x7c)
|1 0x01b7:0x1e5b (PXSRV_FONPUTCATFONT+0x2cd)
|2 0x01a7:0x05aa
|3 0x01b7:0x0768 (PXSRV_FONINITFONTS+0x81)
|4 0x014f:0x03ed (PDOXWIN_@SQLCURCB$Q6CBTYPEULN8CBSCTYPE+0x1b1)
|5 0x013f:0x00ac
|
|0x01b7:0x0c41 (PXSRV_FONGETFACENAME+0x7c):  movw        %es:0x38(%bx),%
dx

   Steps to debug a crash. You may stop at any step, but please
   report the bug and provide as much of the information gathered
   to the bug report as feasible.

    1. Get the reason for the crash. This is usually an access to
       an invalid selector, an access to an out of range address
       in a valid selector, popping a segment register from the
       stack or the like. When reporting a crash, report this
       whole crashdump even if it doesn't make sense to you.
       (In this case it is access to an invalid selector, for %es
       is 0000, as seen in the register dump).
    2. Determine the cause of the crash. Since this is usually a
       primary/secondary reaction to a failed or misbehaving Wine
       function, rerun Wine with the WINEDEBUG=+relay environment
       variable set. This will generate quite a lot of output, but
       usually the reason is located in the last call(s). Those
       lines usually look like this:

|Call KERNEL.90: LSTRLEN(0227:0692 "text") ret=01e7:2ce7 ds=0227
      ^^^^^^^^^  ^       ^^^^^^^^^ ^^^^^^      ^^^^^^^^^    ^^^^
      |          |       |         |           |            |Datasegment
      |          |       |         |           |Return address
      |          |       |         |textual parameter
      |          |       |
      |          |       |Argument(s).  This one is a win16 segmented po
inter.
      |          |Function called.
      |The module, the function is called in.  In this case it is KERNEL
.

|Ret  KERNEL.90: LSTRLEN() retval=0x0004 ret=01e7:2ce7 ds=0227
                                  ^^^^^^
                                  |Returnvalue is 16 bit and has the val
ue 4.

    3. If you have found a misbehaving Wine function, try to find
       out why it misbehaves. Find the function in the source
       code. Try to make sense of the arguments passed. Usually
       there is a WINE_DEFAULT_DEBUG_CHANNEL(<channel>); at the
       beginning of the source file. Rerun wine with the
       WINEDEBUG=+xyz,+relay environment variable set.
       Occasionally there are additional debug channels defined at
       the beginning of the source file in the form
       WINE_DECLARE_DEBUG_CHANNEL(<channel>); If so the offending
       function may also uses one of these alternate channels.
       Look through the the function for TRACE_(<channel>)(" ...
       /n"); and add any additional channels to the commandline.
    4. Additional information on how to debug using the internal
       debugger can be found in programs/winedbg/README.
    5. If this information isn't clear enough or if you want to
       know more about what's happening in the function itself,
       try running wine with WINEDEBUG=+all, which dumps ALL
       included debug information in wine. It is often necessary
       to limit the debug output produced. That can be done by
       piping the output through grep, or alternatively with
       registry keys. See the Section called Configuring +relay
       behaviour for more information.
    6. If even that isn't enough, add more debug output for
       yourself into the functions you find relevant. See The
       section on Debug Logging in this guide for more
       information. You might also try to run the program in gdb
       instead of using the Wine debugger. If you do that, use
       handle SIGSEGV nostop noprint to disable the handling of
       seg faults inside gdb (needed for Win16).
    7. You can also set a breakpoint for that function. Start wine
       using winedbg instead of wine. Once the debugger is running
       enter break KERNEL_LSTRLEN (replace by function you want to
       debug, CASE IS RELEVANT) to set a breakpoint. Then use
       continue to start normal program-execution. Wine will stop
       if it reaches the breakpoint. If the program isn't yet at
       the crashing call of that function, use continue again
       until you are about to enter that function. You may now
       proceed with single-stepping the function until you reach
       the point of crash. Use the other debugger commands to
       print registers and the like.
     __________________________________________________________

Program hangs, nothing happens

   Start the program with winedbg instead of wine. When the
   program locks up switch to the winedbg's terminal and press
   Ctrl-C. This will stop the program and let you debug the
   program as you would for a crash.
     __________________________________________________________

Program reports an error with a Messagebox

   Sometimes programs are reporting failure using more or less
   nondescript messageboxes. We can debug this using the same
   method as Crashes, but there is one problem... For setting up a
   message box the program also calls Wine producing huge chunks
   of debug code.

   Since the failure happens usually directly before setting up
   the Messagebox you can start winedbg and set a breakpoint at
   MessageBoxA (called by win16 and win32 programs) and proceed
   with continue. With WINEDEBUG=+all Wine will now stop directly
   before setting up the Messagebox. Proceed as explained above.

   You can also run wine using WINEDEBUG=+relay wine program.exe
   2>&1 | less -i and in less search for "MessageBox".
     __________________________________________________________

Disassembling programs

   You may also try to disassemble the offending program to check
   for undocumented features and/or use of them.

   The best, freely available, disassembler for Win16 programs is
   Windows Codeback, archive name wcbxxx.zip (e.g. wcb105a.zip).

   Disassembling win32 programs is possible using eg. GoVest by
   Ansgar Trimborn. It can be found here.

   You can also use the newer and better Interactive Disassembler
   (IDA) from DataRescue. Take a look in the AppDB for links to
   various versions of IDA.

   Another popular disassembler is Windows Disassembler 32 from
   URSoft. Look for a file called w32dsm87.zip (or similar) on
   winsite.com or softpedia.com. It seems that Windows
   Disassembler 32 currently has problems working correctly under
   Wine, so use IDA or GoVest.

   Also of considerable fame amongst disassemblers is SoftIce from
   NuMega. That software has since been acquired by CompuWare
   (http://www.compuware.com/) and made part of their Windows
   driver development suite. Newer versions of SoftIce needs to
   run as a Windows Service and therefore won't currently work
   under Wine.

   If nothing works for you, you might try one of the
   disassemblers found in Google's directory.

   Understanding disassembled code is mostly a question of
   exercise. Most code out there uses standard C function entries
   (for it is usually written in C). Win16 function entries
   usually look like that:
push bp
mov bp, sp
... function code ..
retf XXXX       <--------- XXXX is number of bytes of arguments

   This is a FAR function with no local storage. The arguments
   usually start at [bp+6] with increasing offsets. Note, that
   [bp+6] belongs to the rightmost argument, for exported win16
   functions use the PASCAL calling convention. So, if we use
   strcmp(a,b) with a and b both 32 bit variables b would be at
   [bp+6] and a at [bp+10].

   Most functions make also use of local storage in the
   stackframe:
enter 0086, 00
... function code ...
leave
retf XXXX

   This does mostly the same as above, but also adds 0x86 bytes of
   stackstorage, which is accessed using [bp-xx]. Before calling a
   function, arguments are pushed on the stack using something
   like this:
push word ptr [bp-02]   <- will be at [bp+8]
push di                 <- will be at [bp+6]
call KERNEL.LSTRLEN

   Here first the selector and then the offset to the passed
   string are pushed.
     __________________________________________________________

Sample debugging session

   Let's debug the infamous Word SHARE.EXE messagebox:
|marcus@jet $ wine winword.exe
|            +---------------------------------------------+
|            | !  You must leave Windows and load SHARE.EXE|
|            |    before starting Word.                    |
|            +---------------------------------------------+

|marcus@jet $ WINEDEBUG=+relay,-debug wine winword.exe
|CallTo32(wndproc=0x40065bc0,hwnd=000001ac,msg=00000081,wp=00000000,lp=0
0000000)
|Win16 task 'winword': Breakpoint 1 at 0x01d7:0x001a
|CallTo16(func=0127:0070,ds=0927)
|Call WPROCS.24: TASK_RESCHEDULE() ret=00b7:1456 ds=0927
|Ret  WPROCS.24: TASK_RESCHEDULE() retval=0x8672 ret=00b7:1456 ds=0927
|CallTo16(func=01d7:001a,ds=0927)
|     AX=0000 BX=3cb4 CX=1f40 DX=0000 SI=0000 DI=0927 BP=0000 ES=11f7
|Loading symbols: /home/marcus/wine/wine...
|Stopped on breakpoint 1 at 0x01d7:0x001a
|In 16 bit mode.
|Wine-dbg>break MessageBoxA                          <---- Set Breakpoin
t
|Breakpoint 2 at 0x40189100 (MessageBoxA [msgbox.c:190])
|Wine-dbg>c                                            <---- Continue
|Call KERNEL.91: INITTASK() ret=0157:0022 ds=08a7
|     AX=0000 BX=3cb4 CX=1f40 DX=0000 SI=0000 DI=08a7 ES=11d7 EFL=000002
86
|CallTo16(func=090f:085c,ds=0dcf,0x0000,0x0000,0x0000,0x0000,0x0800,0x00
00,0x0000,0x0dcf)
|...                                                   <----- Much debug
output
|Call KERNEL.136: GETDRIVETYPE(0x0000) ret=060f:097b ds=0927
                               ^^^^^^ Drive 0 (A:)
|Ret  KERNEL.136: GETDRIVETYPE() retval=0x0002 ret=060f:097b ds=0927
                                        ^^^^^^  DRIVE_REMOVEABLE
                                                (It is a floppy diskdriv
e.)

|Call KERNEL.136: GETDRIVETYPE(0x0001) ret=060f:097b ds=0927
                               ^^^^^^ Drive 1 (B:)
|Ret  KERNEL.136: GETDRIVETYPE() retval=0x0000 ret=060f:097b ds=0927
                                        ^^^^^^  DRIVE_CANNOTDETERMINE
                                                (I don't have drive B: a
ssigned)

|Call KERNEL.136: GETDRIVETYPE(0x0002) ret=060f:097b ds=0927
                               ^^^^^^^ Drive 2 (C:)
|Ret  KERNEL.136: GETDRIVETYPE() retval=0x0003 ret=060f:097b ds=0927
                                        ^^^^^^ DRIVE_FIXED
                                               (specified as a harddisk)

|Call KERNEL.97: GETTEMPFILENAME(0x00c3,0x09278364"doc",0x0000,0927:8248
) ret=060f:09b1 ds=0927
                                 ^^^^^^           ^^^^^        ^^^^^^^^^
                                 |                |            |buffer f
or fname
                                 |                |temporary name ~docXX
XX.tmp
                                 |Force use of Drive C:.

|Warning: GetTempFileName returns 'C:~doc9281.tmp', which doesn't seem t
o be writable.
|Please check your configuration file if this generates a failure.

   Whoops, it even detects that something is wrong!
|Ret  KERNEL.97: GETTEMPFILENAME() retval=0x9281 ret=060f:09b1 ds=0927
                                          ^^^^^^ Temporary storage ID

|Call KERNEL.74: OPENFILE(0x09278248"C:~doc9281.tmp",0927:82da,0x1012) r
et=060f:09d8 ds=0927
                                    ^^^^^^^^^^^^^^^^ ^^^^^^^^^ ^^^^^^^
                                    |filename        |OFSTRUCT |open mod
e:

                                       OF_CREATE|OF_SHARE_EXCLUSIVE|OF_R
EADWRITE

   This fails, since my C: drive is in this case mounted readonly.
|Ret  KERNEL.74: OPENFILE() retval=0xffff ret=060f:09d8 ds=0927
                                   ^^^^^^ HFILE_ERROR16, yes, it failed.

|Call USER.1: MESSAGEBOX(0x0000,0x09278376"You must close Windows and lo
ad SHARE.EXE before you start Word.",0x00000000,0x1030) ret=060f:084f ds
=0927

   And MessageBox'ed.
|Stopped on breakpoint 2 at 0x40189100 (MessageBoxA [msgbox.c:190])
|190     {              <- the sourceline
In 32 bit mode.
Wine-dbg>

   The code seems to find a writable harddisk and tries to create
   a file there. To work around this bug, you can define C: as a
   networkdrive, which is ignored by the code above.
     __________________________________________________________

Debugging Tips

   Here are some additional debugging tips:

     * If you have a program crashing at such an early loader
       phase that you can't use the Wine debugger normally, but
       Wine already executes the program's start code, then you
       may use a special trick. You should do a

WINEDEBUG=+relay wine program

       to get a listing of the functions the program calls in its
       start function. Now you do a

winedbg winfile.exe

       This way, you get into winedbg. Now you can set a
       breakpoint on any function the program calls in the start
       function and just type c to bypass the eventual calls of
       Winfile to this function until you are finally at the place
       where this function gets called by the crashing start
       function. Now you can proceed with your debugging as usual.
     * If you try to run a program and it quits after showing an
       error messagebox, the problem can usually be identified in
       the return value of one of the functions executed before
       MessageBox(). That's why you should re-run the program with
       e.g.

WINEDEBUG=+relay wine  <program name> &>relmsg

       Then do a more relmsg and search for the last occurrence of
       a call to the string "MESSAGEBOX". This is a line like

Call USER.1: MESSAGEBOX(0x0000,0x01ff1246 "Runtime error 219 at 0004:105
6.",0x00000000,0x1010) ret=01f7:2160 ds=01ff

       In my example the lines before the call to MessageBox()
       look like that:

Call KERNEL.96: FREELIBRARY(0x0347) ret=01cf:1033 ds=01ff
CallTo16(func=033f:0072,ds=01ff,0x0000)
Ret  KERNEL.96: FREELIBRARY() retval=0x0001 ret=01cf:1033 ds=01ff
Call KERNEL.96: FREELIBRARY(0x036f) ret=01cf:1043 ds=01ff
CallTo16(func=0367:0072,ds=01ff,0x0000)
Ret  KERNEL.96: FREELIBRARY() retval=0x0001 ret=01cf:1043 ds=01ff
Call KERNEL.96: FREELIBRARY(0x031f) ret=01cf:105c ds=01ff
CallTo16(func=0317:0072,ds=01ff,0x0000)
Ret  KERNEL.96: FREELIBRARY() retval=0x0001 ret=01cf:105c ds=01ff
Call USER.171: WINHELP(0x02ac,0x01ff05b4 "COMET.HLP",0x0002,0x00000000)
ret=01cf:1070 ds=01ff
CallTo16(func=0117:0080,ds=01ff)
Call WPROCS.24: TASK_RESCHEDULE() ret=00a7:0a2d ds=002b
Ret  WPROCS.24: TASK_RESCHEDULE() retval=0x0000 ret=00a7:0a2d ds=002b
Ret  USER.171: WINHELP() retval=0x0001 ret=01cf:1070 ds=01ff
Call KERNEL.96: FREELIBRARY(0x01be) ret=01df:3e29 ds=01ff
Ret  KERNEL.96: FREELIBRARY() retval=0x0000 ret=01df:3e29 ds=01ff
Call KERNEL.52: FREEPROCINSTANCE(0x02cf00ba) ret=01f7:1460 ds=01ff
Ret  KERNEL.52: FREEPROCINSTANCE() retval=0x0001 ret=01f7:1460 ds=01ff
Call USER.1: MESSAGEBOX(0x0000,0x01ff1246 "Runtime error 219 at 0004:105
6.",0x00000000,0x1010) ret=01f7:2160 ds=01ff

       I think that the call to MessageBox() in this example is
       not caused by a wrong result value of some previously
       executed function (it's happening quite often like that),
       but instead the messagebox complains about a runtime error
       at 0x0004:0x1056.
       As the segment value of the address is only 4, I think that
       that is only an internal program value. But the offset
       address reveals something quite interesting: Offset 1056 is
       very close to the return address of FREELIBRARY():

Call KERNEL.96: FREELIBRARY(0x031f) ret=01cf:105c ds=01ff
                                             ^^^^

       Provided that segment 0x0004 is indeed segment 0x1cf, we
       now we can use IDA to disassemble the part that caused the
       error. We just have to find the address of the call to
       FreeLibrary(). Some lines before that the runtime error
       occurred. But be careful! In some cases you don't have to
       disassemble the main program, but instead some DLL called
       by it in order to find the correct place where the runtime
       error occurred. That can be determined by finding the
       origin of the segment value (in this case 0x1cf).
     * If you have created a relay file of some crashing program
       and want to set a breakpoint at a certain location which is
       not yet available as the program loads the breakpoint's
       segment during execution, you may set a breakpoint to
       GetVersion16/32 as those functions are called very often.
       Then do a c until you are able to set this breakpoint
       without error message.
     __________________________________________________________

Some basic debugger usages

   After starting your program with
winedbg myprog.exe

   the program loads and you get a prompt at the program starting
   point. Then you can set breakpoints:
  b RoutineName      (by routine name) OR
  b *0x812575        (by address)

   Then you hit c (continue) to run the program. It stops at the
   breakpoint. You can type
  step               (to step one line) OR
  stepi              (to step one machine instruction at a time;
                      here, it helps to know the basic 386
                      instruction set)
  info reg           (to see registers)
  info stack         (to see hex values in the stack)
  info local         (to see local variables)
  list <line number> (to list source code)
  x <variable name>  (to examine a variable; only works if code
                      is not compiled with optimization)
  x 0x4269978        (to examine a memory location)
  ?                  (help)
  q                  (quit)

   By hitting Enter, you repeat the last command.
     __________________________________________________________

Useful programs

   Some useful programs:

   GoVest: govest.zip is available from
          http://www.oocities.com/govest/.
          Simple win32 disassembler that works well with Wine.

   IDA:
          IDA Pro is highly recommended, but is not free.
          DataRescue does however make trial versions available.

          Take a look in the AppDB for links to various versions
          of IDA.

   XRAY: http://garbo.uwasa.fi/pub/pc/sysinfo/xray15.zip
          Traces DOS calls (Int 21h, DPMI, ...). Use it with
          Windows to correct file management problems etc.

   pedump:
          ftp://ftp.simtel.net/pub/simtelnet/win95/prog/pedump.zip
          Dumps the imports and exports of a PE (Portable
          Executable) DLL.

   winedump: (included in wine tree)
          Dumps the imports and exports of a PE (Portable
          Executable) DLL.
     __________________________________________________________

Useful memory addresses

   Wine uses several different kinds of memory addresses.

   Win32/"normal" Wine addresses/Linux: linear addresses.
          Linear addresses can be everything from 0x0 up to
          0xffffffff. In Wine on Linux they are often around e.g.
          0x08000000, 0x00400000 (std. Win32 program load
          address), 0x40000000. Every Win32 process has its own
          private 4GB address space (that is, from 0x0 up to
          0xffffffff).

   Win16 "enhanced mode": segmented addresses.
          These are the "normal" Win16 addresses, called SEGPTR.
          They have a segment:offset notation, e.g. 0x01d7:0x0012.
          The segment part usually is a "selector", which always
          has the lowest 3 bits set. Some sample selectors are
          0x1f7, 0x16f, 0x8f. If these bits are set except for the
          lowest bit, as e.g. with 0x1f6,xi then it might be a
          handle to global memory. Just set the lowest bit to get
          the selector in these cases. A selector kind of "points"
          to a certain linear (see above) base address. It has
          more or less three important attributes: segment base
          address, segment limit, segment access rights.

          Example:

          Selector 0x1f7 (0x40320000, 0x0000ffff, r-x) So 0x1f7
          has a base address of 0x40320000, the segment's last
          address is 0x4032ffff (limit 0xffff), and it's readable
          and executable. So an address of 0x1f7:0x2300 would be
          the linear address of 0x40322300.

   DOS/Win16 "standard mode"
          They, too, have a segment:offset notation. But they are
          completely different from "normal" Win16 addresses, as
          they just represent at most 1MB of memory: The segment
          part can be anything from 0 to 0xffff, and it's the same
          with the offset part.

          Now the strange thing is the calculation that's behind
          these addresses: Just calculate segment*16 + offset in
          order to get a "linear DOS" address. So e.g.
          0x0f04:0x3628 results in 0xf040 + 0x3628 = 0x12668. And
          the highest address you can get is 0xfffff (1MB), of
          course. In Wine, this "linear DOS" address of 0x12668
          has to be added to the linear base address of the
          corresponding DOS memory allocated for dosmod in order
          to get the true linear address of a DOS seg:offs
          address. And make sure that you're doing this in the
          correct process with the correct linear address space,
          of course ;-)
     __________________________________________________________

Configuration

Windows Debugging configuration

   The Windows' debugging API uses a registry entry to know which
   debugger to invoke when an unhandled exception occurs (see On
   exceptions for some details). Two values in key
[MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug]

   Determine the behavior:

   Debugger
          This is the command line used to launch the debugger (it
          uses two printf formats (%ld) to pass context dependent
          information to the debugger). You should put here a
          complete path to your debugger (winedbg can of course be
          used, but any other Windows' debugging API aware
          debugger will do). The path to the debugger you choose
          to use must be reachable via one of the DOS drives
          configured under /dosdevices in your $WINEPREFIX or
          ~/.wine folder.

   Auto
          If this value is zero, a message box will ask the user
          if he/she wishes to launch the debugger when an
          unhandled exception occurs. Otherwise, the debugger is
          automatically started.

   A regular Wine registry looks like:
[MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug] 9576
36538
"Auto"=dword:00000001
"Debugger"="winedbg %ld %ld"

   Note Note 1


   Creating this key is mandatory. Not doing so will not fire the
   debugger when an exception occurs.

   Note Note 2


   wineinstall (available in Wine source) sets up this correctly.
   However, due to some limitation of the registry installed, if a
   previous Wine installation exists, it's safer to remove the
   whole
[MACHINE\\Software\\Microsoft\\Windows NT\\CurrentVersion\\AeDebug]

   key before running again wineinstall to regenerate this key.
     __________________________________________________________

WineDbg configuration

   winedbg can be configured through a number of options. Those
   options are stored in the registry, on a per user basis. The
   key is (in my registry)
[HKCU\\Software\\Wine\\WineDbg]

   Those options can be read/written while inside winedbg, as part
   of the debugger expressions. To refer to one of these options,
   its name must be prefixed by a $ sign. For example,
set $BreakAllThreadsStartup = 1

   sets the option BreakAllThreadsStartup to TRUE.

   All the options are read from the registry when winedbg starts
   (if no corresponding value is found, a default value is used),
   and are written back to the registry when winedbg exits (hence,
   all modifications to those options are automatically saved when
   winedbg terminates).

   Here's the list of all options:

   BreakAllThreadsStartup
          Set to TRUE if at all threads start-up the debugger
          stops set to FALSE if only at the first thread startup
          of a given process the debugger stops. FALSE by default.

   BreakOnCritSectTimeOut
          Set to TRUE if the debugger stops when a critical
          section times out (5 minutes); TRUE by default.

   BreakOnAttach
          Set to TRUE if when winedbg attaches to an existing
          process after an unhandled exception, winedbg shall be
          entered on the first attach event. Since the attach
          event is meaningless in the context of an exception
          event (the next event which is the exception event is of
          course relevant), that option is likely to be FALSE.

   BreakOnFirstChance
          An exception can generate two debug events. The first
          one is passed to the debugger (known as a first chance)
          just after the exception. The debugger can then decide
          either to resume execution (see winedbg's cont command)
          or pass the exception up to the exception handler chain
          in the program (if it exists) (winedbg implements this
          through the pass command). If none of the exception
          handlers takes care of the exception, the exception
          event is sent again to the debugger (known as last
          chance exception). You cannot pass on a last exception.
          When the BreakOnFirstChance exception is TRUE, then
          winedbg is entered for both first and last chance
          execptions (to FALSE, it's only entered for last chance
          exceptions).

   AlwaysShowThunk
          Set to TRUE if the debugger, when looking up for a
          symbol from its name, displays all the thunks with that
          name. The default value (FALSE) allows not to have to
          choose between a symbol and all the import thunks from
          all the DLLs using that symbols.
     __________________________________________________________

Configuring +relay behaviour

   When setting WINEDEBUG to +relay and debugging, you might get a
   lot of output. You can limit the output by configuring the
   value RelayExclude in the registry, located under the key:
          [HKCU\\Software\\Wine\\Debug]

   Set the value of RelayExclude to a semicolon-separated list of
   calls to exclude. Example:
   "RtlEnterCriticalSection;RtlLeaveCriticalSection;kernel32.97;ke
   rnel32.98".

   RelayInclude is an option similar to RelayExclude, except that
   functions listed here will be the only ones included in the
   output. Also see section 3.4.3.5 for more options.

   If your application runs too slow with +relay to get meaningful
   output and you're stuck with multi-GB relay log files, but
   you're not sure what to exclude, here's a trick to get you
   started. First, run your application for a minute or so, piping
   it's output to a file on disk:
          WINEDEBUG=+relay wine <appname.exe> &>relay.log

   Then run this command to see which calls are performed the
   most:
          awk -F'(' '{print $1}' < relay.log | awk '{print $2}' | sort |
 uniq -c | sort

   Exclude the bottom-most calls with RelayExclude after making
   sure that they are irrelevant, then run your application again.
     __________________________________________________________

WineDbg Expressions and Variables

Expressions

   Expressions in Wine Debugger are mostly written in a C form.
   However, there are a few discrepancies:

     * Identifiers can take a '!' in their names. This allow
       mainly to access symbols from different DLLs like
       USER32!CreateWindowExA.
     * In cast operation, when specifying a structure or an union,
       you must use the struct or union keyword (even if your
       program uses a typedef).

   When specifying an identifier by its name, if several symbols
   with the same name exist, the debugger will prompt for the
   symbol you want to use. Pick up the one you want from its
   number.

   In lots of cases, you can also use regular expressions for
   looking for a symbol.

   winedbg defines its own set of variables. The configuration
   variables from above are part of them. Some others include:

   $ThreadId
          ID of the W-thread currently examined by the debugger

   $ProcessId
          ID of the W-thread currently examined by the debugger

   <registers>
          All CPU registers are also available, using $ as a
          prefix. You can use info regs to get a list of avaible
          CPU registers

   The $ThreadId and $ProcessId variables can be handy to set
   conditional breakpoints on a given thread or process.
     __________________________________________________________

WineDbg Command Reference

Misc

   Table 1. WineDbg's misc. commands
   abort aborts the debugger
   quit exits the debugger
   attach N attach to a W-process (N is its ID, numeric or
   hexadecimal (0xN)). IDs can be obtained using the info process
   command. Note the info process command returns hexadecimal
   values.
   detach detach from a W-process.
   help prints some help on the commands
   help info prints some help on info commands
     __________________________________________________________

Flow control

   Table 2. WineDbg's flow control commands
   cont, c continue execution until next breakpoint or exception.
   pass pass the exception event up to the filter chain.
   step, s continue execution until next 'C' line of code (enters
   function call)
   next, n continue execution until next 'C' line of code (doesn't
   enter function call)
   stepi, si execute next assembly instruction (enters function
   call)
   nexti, ni execute next assembly instruction (doesn't enter
   function call)
   finish, f execute until current function is exited

   cont, step, next, stepi, nexti can be postfixed by a number
   (N), meaning that the command must be executed N times.
     __________________________________________________________

Breakpoints, watch points

   Table 3. WineDbg's break & watch points
   enable N enables (break|watch)point #N
   disable N disables (break|watch)point #N
   delete N deletes (break|watch)point #N
   cond N removes any existing condition to (break|watch)point N
   cond N <expr> adds condition <expr> to (break|watch)point N.
   <expr> will be evaluated each time the breakpoint is hit. If
   the result is a zero value, the breakpoint isn't triggered
   break * N adds a breakpoint at address N
   break <id> adds a breakpoint at the address of symbol <id>
   break <id> N adds a breakpoint at the address of symbol <id> (N
   ?)
   break N adds a breakpoint at line N of current source file
   break adds a breakpoint at current $PC address
   watch * N adds a watch command (on write) at address N (on 4
   bytes)
   watch <id> adds a watch command (on write) at the address of
   symbol <id>
   info break lists all (break|watch)points (with state)

   You can use the symbol EntryPoint to stand for the entry point
   of the Dll.

   When setting a break/watch-point by <id>, if the symbol cannot
   be found (for example, the symbol is contained in a not yet
   loaded module), winedbg will recall the name of the symbol and
   will try to set the breakpoint each time a new module is loaded
   (until it succeeds).
     __________________________________________________________

Stack manipulation

   Table 4. WineDbg's stack manipulation
   bt print calling stack of current thread
   bt N print calling stack of thread of ID N (note: this doesn't
   change the position of the current frame as manipulated by the
   up and dn commands)
   up goes up one frame in current thread's stack
   up N goes up N frames in current thread's stack
   dn goes down one frame in current thread's stack
   dn N goes down N frames in current thread's stack
   frame N set N as the current frame for current thread's stack
   info local prints information on local variables for current
   function frame
     __________________________________________________________

Directory & source file manipulation

   Table 5. WineDbg's directory & source file manipulation
   show dir prints the list of dir:s where source files are looked
   for
   dir <pathname> adds <pathname> to the list of dir:s where to
   look for source files
   dir deletes the list of dir:s where to look for source files
   symbolfile <pathname> loads external symbol definition
   symbolfile <pathname> N loads external symbol definition
   (applying an offset of N to addresses)
   list lists 10 source lines forwards from current position
   list - lists 10 source lines backwards from current position
   list N lists 10 source lines from line N in current file
   list <path>:N lists 10 source lines from line N in file <path>
   list <id> lists 10 source lines of function <id>
   list * N lists 10 source lines from address N

   You can specify the end target (to change the 10 lines value)
   using the ','. For example:

   Table 6. WineDbg's list command examples
   list 123, 234 lists source lines from line 123 up to line 234
   in current file
   list foo.c:1, 56 lists source lines from line 1 up to 56 in
   file foo.c
     __________________________________________________________

Displaying

   A display is an expression that's evaluated and printed after
   the execution of any winedbg command.

   winedbg will automatically detect if the expression you entered
   contains a local variable. If so, display will only be shown if
   the context is still in the same function as the one the
   debugger was in when the display expression was entered.

   Table 7. WineDbg's displays
   info display lists the active displays
   display print the active displays' values (as done each time
   the debugger stops)
   display <expr> adds a display for expression <expr>
   display /fmt <expr> adds a display for expression <expr>.
   Printing evaluated <expr> is done using the given format (see
   print command for more on formats)
   del display N, undisplay N deletes display #N
     __________________________________________________________

Disassembly

   Table 8. WineDbg's dissassembly
   disas disassemble from current position
   disas <expr> disassemble from address <expr>
   disas <expr>,<expr> disassembles code between addresses
   specified by the two <expr>
     __________________________________________________________

Memory (reading, writing, typing)

   Table 9. WineDbg's memory management
   x <expr> examines memory at <expr> address
   x /fmt <expr> examines memory at <expr> address using format
   /fmt
   print <expr> prints the value of <expr> (possibly using its
   type)
   print /fmt <expr> prints the value of <expr> (possibly using
   its type)
   set <lval> = <expr> writes the value of <expr> in <lval>
   whatis <expr> prints the C type of expression <expr>
   set ! symbol_picker interactive when printing a value, if
   several symbols are found, ask the user which one to pick
   (default)
   set ! symbol_picker scoped when printing a value, give
   precedence to local symbols over global symbols

   /fmt is either /<letter> or /<count><letter> letter can be

   s an ASCII string
   u an Unicode UTF16 string
   i instructions (disassemble)
   x 32 bit unsigned hexadecimal integer
   d 32 bit signed decimal integer
   w 16 bit unsigned hexadecimal integer
   c character (only printable 0x20-0x7f are actually printed)
   b 8 bit unsigned hexadecimal integer
   g GUID
     __________________________________________________________

Information on Wine's internals

   Table 10. WineDbg's Win32 objects management
   info class lists all Windows' classes registered in Wine
   info class <id> prints information on Windows's class <id>
   info share lists all the dynamic libraries loaded in the
   debugged program (including .so files, NE and PE DLLs)
   info share <N> prints information on module at address <N>
   info regs prints the value of the CPU registers
   info all-regs prints the value of the CPU and Floating Point
   registers
   info segment <N> prints information on segment <N> (i386 only)
   info segment lists all allocated segments (i386 only)
   info stack prints the values on top of the stack
   info map lists all virtual mappings used by the debugged
   program
   info map <N> lists all virtual mappings used by the program of
   pid <N>
   info wnd <N> prints information of Window of handle <N>
   info wnd lists all the window hierarchy starting from the
   desktop window
   info process lists all w-processes in Wine session
   info thread lists all w-threads in Wine session
   info exception lists the exception frames (starting from
   current stack frame)
     __________________________________________________________

Debug channels

   It is possible to turn on and off debug messages as you are
   debugging using the set command (only for debug channels
   specified in WINEDEBUG environment variable). See the Chapter
   called Debug Logging for more details on debug channels.

   Table 11. WineDbg's debug channels' management
   set + warn win turn on warn on 'win' channel
   set + win      turn on warn/fixme/err/trace on 'win' channel
   set - win      turn off warn/fixme/err/trace on 'win' channel
   set - fixme    turn off the 'fixme' class
     __________________________________________________________

Other debuggers

GDB mode

   WineDbg can act as a remote monitor for GDB. This allows to use
   all the power of GDB, but while debugging wine and/or any Win32
   application. To enable this mode, just add --gdb to winedbg
   command line. You'll end up on a GDB prompt. You'll have to use
   the GDB commands (not WineDbg's).

   However, some limitation in GDB while debugging wine (see
   below) don't appear in this mode:

     * GDB will correctly present Win32 thread information and
       breakpoint behavior
     * Moreover, it also provides support for the Dwarf II debug
       format (which became the default format (instead of stabs)
       in gcc 3.1).

   A few Wine extensions available through the monitor command.

   Table 12. WineDbg's debug channels' management
   monitor wnd  lists all window in the Wine session
   monitor proc lists all processes in the Wine session
   monitor mem  displays memory mapping of debugged process
     __________________________________________________________

Graphical frontends to gdb

   This section will describe how you can debug Wine using the GDB
   mode of winedbg and some graphical front ends to GDB for those
   of you who really like graphical debuggers.
     __________________________________________________________

DDD

   Use the following steps, in this order:

    1. Start the Wine debugger with a command line like:

        winedbg --gdb --no-start <name_of_exe_to_debug.exe>

    2. Start ddd
    3. In ddd, use the 'Open File' or 'Open Program' to point to
       the Wine executable (which is either wine-pthread or
       wine-kthread depending on your settings).
    4. In the output of 1/, there's a line like

        target remote localhost:32878

       copy that line and paste into ddd command pane (the one
       with the (gdb) prompt)

   The program should now be loaded and up and running. If you
   want, you can also add in 1/ after the name of the exec all the
   needed parameters
     __________________________________________________________

kdbg

   Use the following steps, in this order:

    1. Start the Wine debugger with a command line like:

        winedbg --gdb --no-start <name_of_exe_to_debug.exe>

    2. In the output of 1/, there's a line like

        target remote localhost:32878

       Start kdbg with

kdbg -r localhost:32878 wine

       localhost:32878 is not a fixed value, but has been printed
       in step 1/. 'wine' should also be the full path to the Wine
       executable (which is either wine-pthread or wine-kthread
       depending on your settings).

   The program should now be loaded and up and running. If you
   want, you can also add in 1/ after the name of the exec all the
   needed parameters
     __________________________________________________________

Using other Unix debuggers

   You can also use other debuggers (like gdb), but you must be
   aware of a few items:

   You need to attach the unix debugger to the correct unix
   process (representing the correct windows thread) (you can
   "guess" it from a ps fax for example: When running the
   emulator, usually the first two upids are for the Windows'
   application running the desktop, the first thread of the
   application is generally the third upid; when running a Winelib
   program, the first thread of the application is generally the
   first upid)

   Note

   If you plan to used gdb for a multi-threaded Wine application
   (native or Winelib), then gdb will be able to handle the
   multiple threads directly only if:

     * Wine is running on the pthread model (it won't work in the
       kthread one). See the Wine architecture documentation for
       further details.
     * gdb supports the multi-threading (you need gdb at least 5.0
       for that).

   In the unfortunate case (no direct thread support in gdb
   because one of the above conditions is false), you'll have to
   spawn a different gdb session for each Windows' thread you wish
   to debug (which means no synchronization for debugging purposes
   between the various threads).

   Here's how to get info about the current execution status of a
   certain Wine process:

   Change into your Wine source dir and enter:
$ gdb wine

   Switch to another console and enter ps ax | grep wine to find
   all wine processes. Inside gdb, repeat for all Wine processes:
(gdb) attach PID

   with PID being the process ID of one of the Wine processes. Use
(gdb) bt

   to get the backtrace of the current Wine process, i.e. the
   function call history. That way you can find out what the
   current process is doing right now. And then you can use
   several times:
(gdb) n

   or maybe even
(gdb) b SomeFunction

   and
(gdb) c

   to set a breakpoint at a certain function and continue up to
   that function. Finally you can enter
(gdb) detach

   to detach from the Wine process.
     __________________________________________________________

Using other Windows debuggers

   You can use any Windows' debugging API compliant debugger with
   Wine. Some reports have been made of success with VisualStudio
   debugger (in remote mode, only the hub runs in Wine). GoVest
   fully runs in Wine.
     __________________________________________________________

Main differences between winedbg and regular Unix debuggers

   Table 13. Debuggers comparison
   WineDbg gdb
   WineDbg debugs a Windows' process: the various threads will be
   handled by the same WineDbg session, and a breakpoint will be
   triggered for any thread of the W-process gdb debugs a Windows'
   thread: a separate gdb session is needed for each thread of a
   Windows' process and a breakpoint will be triggered only for
   the w-thread debugged
   WineDbg supports debug information from stabs (standard Unix
   format) and Microsoft's C, CodeView, .DBG GDB supports debug
   information from stabs (standard Unix format) and Dwarf II.
     __________________________________________________________

Debug Logging

   To better manage the large volume of debugging messages that
   Wine can generate, we divide the messages on a component basis,
   and classify them based on the severity of the reported
   problem. Therefore a message belongs to a channel and a class
   respectively.

   This section will describe the debugging classes, how you can
   create a new debugging channel, what the debugging API is, and
   how you can control the debugging output. A picture is worth a
   thousand words, so here are a few examples of the debugging API
   in action:
ERR("lock_count == 0 ... please report\n");
FIXME("Unsupported RTL style!\n");
WARN(": file seems to be truncated!\n");
TRACE("[%p]: new horz extent = %d\n", hwnd, extent );
MESSAGE( "Could not create graphics driver '%s'\n", buffer );
     __________________________________________________________

Debugging classes

   A debugging class categorizes a message based on the severity
   of the reported problem. There is a fixed set of classes, and
   you must carefully choose the appropriate one for your
   messages. There are five classes of messages:

   FIXME
          Messages in this class are meant to signal unimplemented
          features, known bugs, etc. They serve as a constant and
          active reminder of what needs to be done.

   ERR
          Messages in this class indicate serious errors in Wine,
          such as as conditions that should never happen by
          design.

   WARN
          These are warning messages. You should report a warning
          when something unwanted happens, and the function cannot
          deal with the condition. This is seldomly used since
          proper functions can usually report failures back to the
          caller. Think twice before making the message a warning.

   TRACE
          These are detailed debugging messages that are mainly
          useful to debug a component. These are turned off unless
          explicitly enabled.

   MESSAGE
          There messages are intended for the end user. They do
          not belong to any channel. As with warnings, you will
          seldomly need to output such messages.
     __________________________________________________________

Debugging channels

   Each component is assigned a debugging channel. The identifier
   of the channel must be a valid C identifier (reserved word like
   int or static are premitted). To use a new channel, simply use
   it in your code. It will be picked up automatically by the
   build process.

   Typically, a file contains code pertaining to only one
   component, and as such, there is only one channel to output to.
   You can declare a default chanel for the file using the
   WINE_DEFAULT_DEBUG_CHANNEL() macro:
#include "wine/debug.h"

WINE_DEFAULT_DEBUG_CHANNEL(xxx);
...

    FIXME("some unimplemented feature", ...);
...
    if (zero != 0)
        ERR("This should never be non-null: %d", zero);
...

   In rare situations there is a need to output to more than one
   debug channel per file. In such cases, you need to declare all
   the additional channels at the top of the file, and use the
   _-version of the debugging macros:
#include "wine/debug.h"

WINE_DEFAULT_DEBUG_CHANNEL(xxx);
WINE_DECLARE_DEBUG_CHANNEL(yyy);
WINE_DECLARE_DEBUG_CHANNEL(zzz);
...

    FIXME("this one goes to xxx channel");
...
    FIXME_(yyy)("Some other msg for the yyy channel");
...
    WARN_(zzz)("And yet another msg on another channel!");
...
     __________________________________________________________

Are we debugging?

   To test whether the debugging channel xxx is enabled, use the
   TRACE_ON, WARN_ON, FIXME_ON, or ERR_ON macros. For example:
if(TRACE_ON(atom)){
    ...blah...
}

   You should normally need to test only if TRACE_ON, all the
   others are very seldomly used. With careful coding, you can
   avoid the use of these macros, which is generally desired.
     __________________________________________________________

Helper functions

   Resource identifiers can be either strings or numbers. To make
   life a bit easier for outputting these beasts (and to help you
   avoid the need to build the message in memory), I introduced a
   new function called debugres.

   The function is defined in wine/debug.h and has the following
   prototype:
LPSTR debugres(const void *id);

   It takes a pointer to the resource id and returns a nicely
   formatted string of the identifier (which can be a string or a
   number, depending on the value of the high word). Numbers are
   formatted as such:
#xxxx

   while strings as:
'some-string'

   Simply use it in your code like this:
#include "wine/debug.h"

...

   TRACE("resource is %s", debugres(myresource));

   Many times strings need to be massaged before output: they may
   be NULL, contain control characters, or they may be too long.
   Similarly, Unicode strings need to be converted to ASCII for
   usage with the debugging API. For all this, you can use the
   debugstr_[aw]n? familly of functions:
HANDLE32 WINAPI YourFunc(LPCSTR s)
{
    FIXME("(%s): stub\n", debugstr_a(s));
}
     __________________________________________________________

Controlling the debugging output

   It is possible to turn on and off debugging output from within
   the debugger using the set command. Please see the WineDbg
   Command Reference section (the Section called Debug channels in
   the Chapter called Debugging Wine) for how to do this.

   You can do the same using the task manager (taskmgr) and
   selecting your application in the application list. Right
   clicking on the application, and selecting the debug option in
   the popup menu, will let you select the modifications you want
   on the debug channels.

   Another way to conditionally log debug output (e.g. in case of
   very large installers which may create gigabytes of log output)
   is to create a pipe:
        $ mknod /tmp/debug_pipe p

   and then to run wine like that:
        $ WINEDEBUG=+relay,+snoop wine setup.exe &>/tmp/debug_pipe

   Since the pipe is initially blocking (and thus wine as a
   whole), you have to activate it by doing:
        $ cat /tmp/debug_pipe

   (press Ctrl-C to stop pasting the pipe content)

   Once you are about to approach the problematic part of the
   program, you just do:
        $ cat /tmp/debug_pipe >/tmp/wine.log

   to capture specifically the part that interests you from the
   pipe without wasting excessive amounts of HDD space and slowing
   down installation considerably.

   The WINEDEBUG environment variable controls the output of the
   debug messages. It has the following syntax: WINEDEBUG=
   [yyy]#xxx[,[yyy1]#xxx1]*

     * where # is either + or -
     * when the optional class argument (yyy) is not present, then
       the statement will enable(+)/disable(-) all messages for
       the given channel (xxx) on all classes. For example:

WINEDEBUG=+reg,-file

       enables all messages on the reg channel and disables all
       messages on the file channel.
     * when the optional class argument (yyy) is present, then the
       statement will enable (+)/disable(-) messages for the given
       channel (xxx) only on the given class. For example:

WINEDEBUG=trace+reg,warn-file

       enables trace messages on the reg channel and disables
       warning messages on the file channel.
     * also, the pseudo-channel all is also supported and it has
       the intuitive semantics:

    WINEDEBUG=+all      -- enables all debug messages
    WINEDEBUG=-all      -- disables all debug messages
    WINEDEBUG=yyy+all   -- enables debug messages for class yyy on all
                           channels.
    WINEDEBUG=yyy-all   -- disables debug messages for class yyy on all
                           channels.

       So, for example:

    WINEDEBUG=warn-all  -- disables all warning messages.

   Also, note that at the moment:

     * the FIXME and ERR classes are enabled by default
     * the TRACE and WARN classes are disabled by default
     __________________________________________________________

Compiling Out Debugging Messages

   To compile out the debugging messages, provide configure with
   the following options:
    --disable-debug      -- turns off TRACE, WARN, and FIXME (and DUMP).
    --disable-trace      -- turns off TRACE only.

   This will result in an executable that, when stripped, is about
   15%-20% smaller. Note, however, that you will not be able to
   effectively debug Wine without these messages.

   This feature has not been extensively tested--it may subtly
   break some things.
     __________________________________________________________

A Few Notes on Style

   This new scheme makes certain things more consistent but there
   is still room for improvement by using a common style of debug
   messages. Before I continue, let me note that the output format
   is the following:
yyy:xxx:fff <message>

where:
  yyy = the class (fixme, err, warn, trace)
  xxx = the channel (atom, win, font, etc)
  fff = the function name

   these fields are output automatically. All you have to provide
   is the <message> part.

   So here are some ideas:

     * do not include the name of the function: it is included
       automatically
     * if you want to output the parameters of the function, do it
       as the first thing and include them in parentheses, like
       this:

TRACE("(%d, %p, ...)\n", par1, par2, ...);

     * if you want to name a parameter, use = :

TRACE("(fd=%d, file=%s): stub\n", fd, name);

     * for stubs, you should output a FIXME message. I suggest
       this style:

FIXME("(%x, %d, ...): stub\n", par1, par2, ...);

     * try to output one line per message. That is, the format
       string should contain only one \n and it should always
       appear at the end of the string.
     * if the output string needs to be dynamically constructed,
       render it in memory before outputting it:

char buffer[128] = "";

if (flags & FLAG_A) strcat(buffer, "FLAG_A ");
if (flags & FLAG_B) strcat(buffer, "FLAG_B ");
if (flags & FLAG_C) strcat(buffer, "FLAG_C ");
TRACE("flags = %s\n", buffer);

       Most of the time however, it is better to create a helper
       function that renders to a temporary buffer:

static const char *dbgstr_flags(int flags)
{
    char buffer[128] = "";

    if (flags & FLAG_A) strcat(buffer, "FLAG_A ");
    if (flags & FLAG_B) strcat(buffer, "FLAG_B ");
    if (flags & FLAG_C) strcat(buffer, "FLAG_C ");
    return wine_dbg_sprintf("flags = %s\n\n", buffer);
}

...

TRACE("flags = %s\n", dbgstr_flags(flags));
     __________________________________________________________

Other debugging techniques

Understanding undocumented APIs

   Some background: On the i386 class of machines, stack entries
   are usually dword (4 bytes) in size, little-endian. The stack
   grows downward in memory. The stack pointer, maintained in the
   esp register, points to the last valid entry; thus, the
   operation of pushing a value onto the stack involves
   decrementing esp and then moving the value into the memory
   pointed to by esp (i.e., push p in assembly resembles *(--esp)
   = p; in C). Removing (popping) values off the stack is the
   reverse (i.e., pop p corresponds to p = *(esp++); in C).

   In the stdcall calling convention, arguments are pushed onto
   the stack right-to-left. For example, the C call myfunction(40,
   20, 70, 30); is expressed in Intel assembly as:
    push 30
    push 70
    push 20
    push 40
    call myfunction

   The called function is responsible for removing the arguments
   off the stack. Thus, before the call to myfunction, the stack
   would look like:
             [local variable or temporary]
             [local variable or temporary]
              30
              70
              20
    esp ->    40

   After the call returns, it should look like:
             [local variable or temporary]
    esp ->   [local variable or temporary]

   To restore the stack to this state, the called function must
   know how many arguments to remove (which is the number of
   arguments it takes). This is a problem if the function is
   undocumented.

   One way to attempt to document the number of arguments each
   function takes is to create a wrapper around that function that
   detects the stack offset. Essentially, each wrapper assumes
   that the function will take a large number of arguments. The
   wrapper copies each of these arguments into its stack, calls
   the actual function, and then calculates the number of
   arguments by checking esp before and after the call.

   The main problem with this scheme is that the function must
   actually be called from another program. Many of these
   functions are seldom used. An attempt was made to aggressively
   query each function in a given library (ntdll.dll) by passing
   64 arguments, all 0, to each function. Unfortunately, Windows
   NT quickly goes to a blue screen of death, even if the program
   is run from a non-administrator account.

   Another method that has been much more successful is to attempt
   to figure out how many arguments each function is removing from
   the stack. This instruction, ret hhll (where hhll is the number
   of bytes to remove, i.e. the number of arguments times 4),
   contains the bytes 0xc2 ll hh in memory. It is a reasonable
   assumption that few, if any, functions take more than 16
   arguments; therefore, simply searching for hh == 0 && ll < 0x40
   starting from the address of a function yields the correct
   number of arguments most of the time.

   Of course, this is not without errors. ret 00ll is not the only
   instruction that can have the byte sequence 0xc2 ll 0x0; for
   example, push 0x000040c2 has the byte sequence 0x68 0xc2 0x40
   0x0 0x0, which matches the above. Properly, the utility should
   look for this sequence only on an instruction boundary;
   unfortunately, finding instruction boundaries on an i386
   requires implementing a full disassembler -- quite a daunting
   task. Besides, the probability of having such a byte sequence
   that is not the actual return instruction is fairly low.

   Much more troublesome is the non-linear flow of a function. For
   example, consider the following two functions:
    somefunction1:
        jmp  somefunction1_impl

    somefunction2:
        ret  0004

    somefunction1_impl:
        ret  0008

   In this case, we would incorrectly detect both somefunction1
   and somefunction2 as taking only a single argument, whereas
   somefunction1 really takes two arguments.

   With these limitations in mind, it is possible to implement
   more stubs in Wine and, eventually, the functions themselves.
     __________________________________________________________

How to do regression testing using Git

   A problem that can happen sometimes is 'it used to work before,
   now it doesn't anymore...'. Here is a step by step procedure to
   try to pinpoint when the problem occurred. This is NOT for
   casual users.

    1. Clone the "Git" repository from winehq. It's more than
       100Mb, so it may take some time with a slow Internet
       connection.
    2. If you found that something broke between wine-1.1.42 and
       wine-1.1.44 (these are [WWW] release tags). To start
       regression testing we run:

git bisect start
git bisect good wine-1.1.42
git bisect bad wine-1.1.44

       If you have exact date/time instead of a release you will
       need to use sha1 IDs from git log.
    3. Having told Git when things were working and when they
       broke, it will automatically "position" your source tree to
       the middle. So all you need to do is build the source:

./configure && make clean && make depend && make
./wine 'c:\test.exe'

       If the version of Wine that Git picked still has the bug,
       run:

git bisect bad

       and if it does not, run:

git bisect good

       When you run this command, Git will checkout a new version
       of Wine for you to rebuild, so repeat this step again. When
       the regression has been isolated, git will inform you.
       To find out what's left to test, try:

git bisect visualize.

    4. When you have found the bad patch and want to go back to
       the current HEAD run:

git bisect reset

    5. If you find the patch that is the cause of the problem, you
       have almost won; report about it to Wine Bugzilla or
       subscribe to wine-devel and post it there. There is a
       chance that the author will jump in to suggest a fix; or
       there is always the possibility to look hard at the patch
       until it is coerced to reveal where is the bug :-)
     __________________________________________________________

Which code has been tested?

   Deciding what code should be tested next can be a difficult
   decision. And in any given project, there is always code that
   isn't tested where bugs could be lurking. This section goes
   over how to identify these sections using a tool called gcov.

   To use gcov on wine, do the following:

    1. In order to activate code coverage in the wine source code,
       when running make set EXTRACFLAGS and LDFLAGS like so make
       EXTRACFLAGS=--coverage LDFLAGS=--coverage. Note that this
       can be done at any directory level. Since compile and run
       time are significantly increased by these flags, you may
       want to only use these flags inside a given dll directory.
    2. Run any application or test suite.
    3. Run gcov on the file which you would like to know more
       about code coverage.

   The following is an example situation when using gcov to
   determine the coverage of a file could be helpful. We'll use
   the dlls/advapi32/registry.c file. At one time the code in this
   file was not fully tested (as it may still be). For example at
   the time of this writing, the function RegSetValueW had the
   following lines in it:
if (name && name[0])  /* need to create the subkey */
{
    if ((ret = RegCreateKeyW( hkey, name, &subkey )) != ERROR_SUCCESS) r
eturn ret;
}

   Currently there are a few tests written to test this function.
   However, these tests don't check that everything is correct.
   Using gcov and directed tests, we can validate the correctness
   of this line of code. First, we see what has been tested
   already by running gcov on the file. To do this, do the
   following:
cd dlls/advapi32
make clean && make EXTRACFLAGS=--coverage LDFLAGS=--coverage
cd tests
make test
cd ..
gcov registry.c
less registry.c.gcov

   The interesting code part looks like this in registry.c.gcov:
        4: 1273:    if (name && name[0])  /* need to create the subkey *
/
        -: 1274:    {
    #####: 1275:        if ((ret = RegCreateKeyW( hkey, name, &subkey ))
 != ERROR_SUCCESS) return ret;
        -: 1276:    }

   gcov output consists of three components: the number of times a
   line was run, the line number, and the actual text of the line.
   Note: If a line is optimized out by the compiler, it will
   appear as if it was never run. Line 1275 is never executed,
   most likely because "name" is never passed to the function. In
   order to validate this line, we need to do two things. First,
   we must write the test:
ret = RegSetValueW(hkey_main, name1W, REG_SZ, string1W, sizeof(string1W)
);
ok(ret == ERROR_SUCCESS, "RegSetValueW failed: %d, GLE=%d\n", ret, GetLa
stError());
test_hkey_main_Value_A(name1A, string1A, sizeof(string1A));
test_hkey_main_Value_W(name1W, string1W, sizeof(string1W));

   Once we add in this test case, we now want to know if the line
   in question is run by this test and works as expected. You
   should be in the same directory as in the previous command
   example. The only difference is that we have to remove the
   *.gcdafilename> files in order to start the count over. (If we
   leave the files then the number of times the line is run is
   just added, e.g. line 545 below would be run 19 times.) We
   remove the *.gcov files because they are out of date and need
   to be recreated.
rm *.gcda *.gcov
cd tests
make
make test
cd ..
cd ..
gcov registry.c
less registry.c.gcov

   The interesting code part looks like this in registry.c.gcov:
        5: 1273:    if (name && name[0])  /* need to create the subkey *
/
        -: 1274:    {
        1: 1275:        if ((ret = RegCreateKeyW( hkey, name, &subkey ))
 != ERROR_SUCCESS) return ret;
        -: 1276:    }

   Based on gcov, we now know that line 1275 is executed once. And
   since all of our other tests have remain unchanged, we can
   assume that the one time it is executed is to satisfy the
   testcase we added where we check for it. Thus we have validated
   a line of code. While this is a cursory example, it
   demonstrates the potential usefulness of this tool.

   For a further in depth description of gcov, the official gcc
   compiler suite page for gcov is
   http://gcc.gnu.org/onlinedocs/gcc/Gcov.html.
     __________________________________________________________

Coding Practice

   This chapter describes the relevant coding practices in Wine,
   that you should be aware of before doing any serious
   development in Wine.
     __________________________________________________________

Patch Format

   Patches are submitted via email to the Wine patches mailing
   list, <wine-patches@winehq.org>. Your patch should include:

     * A meaningful subject (very short description of patch)
     * A long (paragraph) description of what was wrong and what
       is now better. (recommended)
     * A change log entry (short description of what was changed).
     * The patch in "Git" format

   To generate a patch using Git, first commit it to your local
   tree.

   If you are adding a file, use git add. Commit the change using
   git commit. The commit message will be sent with your patch,
   and recorded in the commit log.

   After committing the patch, you can extract it using git
   format-patch and send it to wine-patches using git imap-send or
   simply attaching it to your mail manually.
     __________________________________________________________

Some notes about style

   There are a few conventions about coding style that have been
   adopted over the years of development. The rational for these
   "rules" is explained for each one.

     * No HTML mail, since patches should be in-lined and HTML
       turns the patch into garbage. Also it is considered bad
       etiquette as it uglifies the message, and is not viewable
       by many of the subscribers.
     * Only one change set per patch. Patches should address only
       one bug/problem at a time. If a lot of changes need to be
       made then it is preferred to break it into a series of
       patches. This makes it easier to find regressions.
     * Tabs are not forbidden but discouraged. A tab is defined as
       8 characters and the usual amount of indentation is 4
       characters.
     * C++ style comments are discouraged since some compilers
       choke on them.
     * Commenting out a block of code is usually done by enclosing
       it in #if 0 ... #endif Statements. For example.


/* note about reason for commenting block */
#if 0
code
code /* comments */
code
#endif

       The reason for using this method is that it does not
       require that you edit comments that may be inside the block
       of code.
     * Patches should be in-lined (if you can configure your email
       client to not wrap lines), or attached as plain text
       attachments so they can be read inline. This may mean some
       more work for you. However it allows others to review your
       patch easily and decreases the chances of it being
       overlooked or forgotten.
     * Code is usually limited to 100 columns. It generally makes
       code easier to read.
     * If the patch fixes a bug in Bugzilla please provide a link
       to the bug in the comments of the patch. This will make it
       easier for the maintainers of Bugzilla.
     __________________________________________________________

Inline attachments with Outlook Express

   Outlook Express is notorious for mangling attachments. Giving
   the patch a .txt extension and attaching will solve the problem
   for most mailers including Outlook. Also, there is a way to
   enable Outlook Express to send .diff attachments.

   You need the following two things to make it work.

    1. Make sure that .diff files have \r\n line ends, because if
       OE detects that there is no \r\n line endings it switches
       to quoted-printable format attachments.
    2. Using regedit add key "Content Type" with value
       "text/plain" to the .diff extension under HKEY_CLASSES_ROOT
       (same as for .txt extension). This tells OE to use
       Content-Type: text/plain instead of
       application/octet-stream.

   Item #1 is important. After you hit the "Send" button, go to
   "Outbox" and using "Properties" verify the message source to
   make sure that the mail has the correct format. You might want
   to send several test emails to yourself too.
     __________________________________________________________

Alexandre's Bottom Line

   "The basic rules are: no attachments, no MIME crap, no line
   wrapping, a single patch per mail. Basically if I can't do "cat
   raw_mail | patch -p0" it's in the wrong format."
     __________________________________________________________

Quality Assurance

   (Or, "How do I get Alexandre to apply my patch quickly so I can
   build on it and it will not go stale?")

   Make sure your patch applies to the current Git HEAD revisions.
   If a bunch of patches are committed that may affect whether
   your patch will apply cleanly then verify that your patch does
   apply! git fetch; git rebase origin is your friend!

   Patches must not break building Wine or cause test failures.
   Adding dead code should also be avoided.

   Save yourself some embarrassment and run your patched code
   against more than just your current test example. Experience
   will tell you how much effort to apply here. If there are any
   conformance tests for the code you're working on, run them and
   make sure they still pass after your patch is applied. Running
   tests can be done by running make test. You may need to run
   make testclean to undo the results of a previous test run. See
   the "testing" guide for more details on Wine's conformance
   tests.
     __________________________________________________________

Porting Wine to new Platforms

   This document provides a few tips on porting Wine to your
   favorite (UNIX-based) operating system.
     __________________________________________________________

Why ifdef MyOS is probably a mistake.

   Operating systems change. Maybe yours doesn't have the foo.h
   header, but maybe a future version will have it. If you want to
   #include <foo.h>, it doesn't matter what operating system you
   are using; it only matters whether foo.h is there.

   Furthermore, operating systems change names or "fork" into
   several ones. An #ifdef MyOs will break over time.

   If you use the feature of autoconf -- the Gnu
   auto-configuration utility -- wisely, you will help future
   porters automatically because your changes will test for
   features, not names of operating systems. A feature can be many
   things:

     * existence of a header file
     * existence of a library function
     * existence of libraries
     * bugs in header files, library functions, the compiler, ...

   You will need Gnu Autoconf, which you can get from your
   friendly Gnu mirror. This program takes Wine's configure.ac
   file and produces a configure shell script that users use to
   configure Wine to their system.

   There are exceptions to the "avoid #ifdef MyOS" rule. Wine, for
   example, needs the internals of the signal stack -- that cannot
   easily be described in terms of features. Moreover, you cannot
   use autoconf's HAVE_* symbols in Wine's headers, as these may
   be used by Winelib users who may not be using a configure
   script.

   Let's now turn to specific porting problems and how to solve
   them.
     __________________________________________________________

MyOS doesn't have the foo.h header!

   This first step is to make autoconf check for this header. In
   configure.in you add a segment like this in the section that
   checks for header files (search for "header files"):
AC_CHECK_HEADER(foo.h, AC_DEFINE(HAVE_FOO_H))

   If your operating system supports a header file with the same
   contents but a different name, say bar.h, add a check for that
   also.

   Now you can change
#include <foo.h>

   to
#ifdef HAVE_FOO_H
#include <foo.h>
#elif defined (HAVE_BAR_H)
#include <bar.h>
#endif

   If your system doesn't have a corresponding header file even
   though it has the library functions being used, you might have
   to add an #else section to the conditional. Avoid this if you
   can.

   You will also need to add #undef HAVE_FOO_H (etc.) to
   include/config.h.in

   Finish up with make configure and ./configure.
     __________________________________________________________

MyOS doesn't have the bar function!

   A typical example of this is the memmove function. To solve
   this problem you would add memmove to the list of functions
   that autoconf checks for. In configure.in you search for
   AC_CHECK_FUNCS and add memmove. (You will notice that someone
   already did this for this particular function.)

   Secondly, you will also need to add #undef HAVE_BAR to
   include/config.h.in

   The next step depends on the nature of the missing function.

   Case 1:
          It's easy to write a complete implementation of the
          function. (memmove belongs to this case.)

          You add your implementation in misc/port.c surrounded by
          #ifndef HAVE_MEMMOVE and #endif.

          You might have to add a prototype for your function. If
          so, include/miscemu.h might be the place. Don't forget
          to protect that definition by #ifndef HAVE_MEMMOVE and
          #endif also!

   Case 2:
          A general implementation is hard, but Wine is only using
          a special case.

          An example is the various wait calls used in
          SIGNAL_child from loader/signal.c. Here we have a
          multi-branch case on features:

#ifdef HAVE_THIS
...
#elif defined (HAVE_THAT)
...
#elif defined (HAVE_SOMETHING_ELSE)
...
#endif

          Note that this is very different from testing on
          operating systems. If a new version of your operating
          systems comes out and adds a new function, this code
          will magically start using it.

   Finish up with make configure and ./configure.
     __________________________________________________________

Adding New Languages

   This file documents the necessary procedure for adding a new
   language to the list of languages that Wine can display system
   menus and forms in. Adding new translations is not hard as it
   requires no programming knowledge or special skills.

   Language dependent resources reside in files named
   somefile_Xx.rc or Xx.rc, where Xx is your language abbreviation
   (look for it in include/winnls.h). These are included in a
   master file named somefile.rc or rsrc.rc, located in the same
   directory as the language files.

   To add a new language to one of these resources you need to
   make a copy of the English resource (located in the
   somefile_En.rc file) over to your somefile_Xx.rc file, include
   this file in the master somefile.rc file, and edit the new file
   to translate the English text. You may also need to rearrange
   some of the controls to better fit the newly translated
   strings. Test your changes to make sure they properly layout on
   the screen.

   In menus, the character "&" means that the next character will
   be highlighted and that pressing that letter will select the
   item. You should place these "&" characters suitably for your
   language, not just copy the positions from English. In
   particular, items within one menu should have different
   highlighted letters.

   To get a list of the files that need translating, run the
   following command in the root of your Wine tree: find -name
   "*En.rc".

   When adding a new language, also make sure the parameters
   defined in ./dlls/kernel/nls/*.nls fit your local habits and
   language.
     __________________________________________________________

Writing Conformance tests

Introduction

   The Windows API follows no standard, it is itself a de facto
   standard, and deviations from that standard, even small ones,
   often cause applications to crash or misbehave in some way.

   The question becomes, "How do we ensure compliance with that
   standard?" The answer is, "By using the API documentation
   available to us and backing that up with conformance tests."
   Furthermore, a conformance test suite is the most accurate (if
   not necessarily the most complete) form of API documentation
   and can be used to supplement the Windows API documentation.

   Writing a conformance test suite for more than 10000 APIs is no
   small undertaking. Fortunately it can prove very useful to the
   development of Wine way before it is complete.

     * The conformance test suite must run on Windows. This is
       necessary to provide a reasonable way to verify its
       accuracy. Furthermore the tests must pass successfully on
       all Windows platforms (tests not relevant to a given
       platform should be skipped).
       A consequence of this is that the test suite will provide a
       great way to detect variations in the API between different
       Windows versions. For instance, this can provide insights
       into the differences between the, often undocumented, Win9x
       and NT Windows families.
       However, one must remember that the goal of Wine is to run
       Windows applications on Linux, not to be a clone of any
       specific Windows version. So such variations must only be
       tested for when relevant to that goal.
     * Writing conformance tests is also an easy way to discover
       bugs in Wine. Of course, before fixing the bugs discovered
       in this way, one must first make sure that the new tests do
       pass successfully on at least the Wine Test Bot base VMs.
       Bugs discovered this way should also be easier to fix.
       Unlike some mysterious application crashes, when a
       conformance test fails, the expected behavior and APIs
       tested for are known thus greatly simplifying the
       diagnosis.
     * To detect regressions. Simply running the test suite
       regularly in Wine turns it into a great tool to detect
       regressions. When a test fails, one immediately knows what
       was the expected behavior and which APIs are involved. Thus
       regressions caught this way should be detected earlier,
       because it is easy to run all tests on a regular basis, and
       be easier to fix because of the reduced diagnosis work.
     * Tests written in advance of the Wine development (possibly
       even by non Wine developers) can also simplify the work of
       the future implementer by making it easier for him to check
       the correctness of his code.
     * Conformance tests will also come in handy when testing Wine
       on new (or not as widely used) architectures such as
       FreeBSD, Solaris x86 or even non-x86 systems. Even when the
       port does not involve any significant change in the thread
       management, exception handling or other low-level aspects
       of Wine, new architectures can expose subtle bugs that can
       be hard to diagnose when debugging regular (complex)
       applications.
     __________________________________________________________

What to test for?

   The first thing to test for is the documented behavior of APIs
   and such as CreateFile. For instance one can create a file
   using a long pathname, check that the behavior is correct when
   the file already exists, try to open the file using the
   corresponding short pathname, convert the filename to Unicode
   and try to open it using CreateFileW, and all other things
   which are documented and that applications rely on.

   While the testing framework is not specifically geared towards
   this type of tests, it is also possible to test the behavior of
   Windows messages. To do so, create a window, preferably a
   hidden one so that it does not steal the focus when running the
   tests, and send messages to that window or to controls in that
   window. Then, in the message procedure, check that you receive
   the expected messages and with the correct parameters.

   For instance you could create an edit control and use
   WM_SETTEXT to set its contents, possibly check length
   restrictions, and verify the results using WM_GETTEXT.
   Similarly one could create a listbox and check the effect of
   LB_DELETESTRING on the list's number of items, selected items
   list, highlighted item, etc. For concrete examples, see
   dlls/user32/tests/win.c and the related tests.

   However, undocumented behavior should not be tested for unless
   there is an application that relies on this behavior, and in
   that case the test should mention that application, or unless
   one can strongly expect applications to rely on this behavior,
   typically APIs that return the required buffer size when the
   buffer pointer is NULL.
     __________________________________________________________

Running the tests in Wine

   The simplest way to run the tests in Wine is to type 'make
   test' in the Wine sources top level directory. This will run
   all the Wine conformance tests.

   The tests for a specific Wine library are located in a 'tests'
   directory in that library's directory. Each test is contained
   in a file (e.g. dlls/kernel/tests/thread.c). Each file itself
   contains many checks concerning one or more related APIs.

   So to run all the tests related to a given Wine library, go to
   the corresponding 'tests' directory and type 'make test'. This
   will compile the tests, run them, and create an 'xxx.ok' file
   for each test that passes successfully. And if you only want to
   run the tests contained in the thread.c file of the kernel
   library, you would do:
$ cd dlls/kernel/tests
$ make thread.ok

   Note that if the test has already been run and is up to date
   (i.e. if neither the kernel library nor the thread.c file has
   changed since the thread.ok file was created), then make will
   say so. To force the test to be re-run, delete the thread.ok
   file, and run the make command again.

   You can also run tests manually using a command similar to the
   following:
$ ../../../tools/runtest -q -M kernel32.dll -p kernel32_test.exe.so thre
ad.c
$ ../../../tools/runtest -P wine -p kernel32_test.exe.so thread.c
thread.c: 86 tests executed, 5 marked as todo, 0 failures.

   The '-P wine' option defines the platform that is currently
   being tested and is used in conjunction with the 'todo'
   statements (see below). Remove the '-q' option if you want the
   testing framework to report statistics about the number of
   successful and failed tests. Run runtest -h for more details.
     __________________________________________________________

Cross-compiling the tests with MinGW

Setup of the MinGW cross-compiling environment

   Here are some instructions to setup MinGW on different Linux
   distributions and *BSD.
     __________________________________________________________

Debian GNU/Linux like deb systems

   This includes Debian GNU/Linux, Ubuntu, etc. The following step
   should probably work on any deb based system.

   Run apt-get install mingw32.
     __________________________________________________________

Red Hat Linux like rpm systems

   This includes Fedora, Red Hat Enterprise Linux, Mandrake, most
   probably SuSE Linux too, etc. But this list isn't exhaustive;
   The following step should probably work on any rpm based
   system.

   Run yum install mingw32-gcc.
     __________________________________________________________

*BSD

   The *BSD systems have in their ports collection a port for the
   MinGW cross-compiling environment. Please see the documentation
   of your system about how to build and install a port.
     __________________________________________________________

Compiling the tests

   Having the cross-compiling environment set up the generation of
   the Windows executables is easy by using the Wine build system.

   If you had already run configure, then delete config.cache and
   re-run configure. You can then run make crosstest. To sum up:
$ rm config.cache
$ ./configure
$ make crosstest
     __________________________________________________________

Building and running the tests on Windows

Using pre-compiled binaries

   The simplest solution is to visit test.winehq.org and download
   the latest version of winetest at the bottom of the page. This
   executable contains all the Wine conformance tests, runs them
   and reports the results.

   You can also get the older versions from Paul Millar's website.
     __________________________________________________________

With Visual C++

     * If you are using Visual Studio 6, make sure you have the
       "processor pack" from
       http://msdn.microsoft.com/vstudio/downloads/tools/ppack/def
       ault.aspx. The processor pack fixes "error C2520:
       conversion from unsigned __int64 to double not implemented,
       use signed __int64". However note that the "processor pack"
       is incompatible with Visual Studio 6.0 Standard Edition,
       and with the Visual Studio 6 Service Pack 6. If you are
       using Visual Studio 7 or greater you do not need the
       processor pack. In either case it is recommended to the
       most recent compatible Visual Studio service pack. If are
       using Visual Studio Express and you need specific libraries
       like ntdll.lib that don't ship with Visual Studio Express,
       you will need the Windows Driver Development Kit (DDK)
       which is part of the Windows Developer Kit.
     * get the Wine sources
     * Run msvcmaker to generate Visual C++ project files for the
       tests. 'msvcmaker' is a perl script so you may be able to
       run it on Windows.

$ ./tools/winapi/msvcmaker --no-wine

     * If the previous steps were done on your Linux development
       machine, make the Wine sources accessible to the Windows
       machine on which you are going to compile them. Typically
       you would do this using Samba but copying them altogether
       would work too.
     * On the Windows machine, open the winetest.dsw workspace.
       This will load each test's project. For each test there are
       two configurations: one compiles the test with the Wine
       headers, and the other uses the Microsoft headers.
     * If you choose the "Win32 MSVC Headers" configuration, most
       of the tests will not compile with the regular Visual
       Studio headers. So to use this configuration, download and
       install a recent Platform SDK as well as the latest DirectX
       SDK. Then, configure Visual Studio to use these SDK's
       headers and libraries. Alternately you could go to the
       Project+Settings... menu and modify the settings
       appropriately, but you would then have to redo this
       whenever you rerun msvcmaker.
     * Open the Build+Batch build... menu and select the tests and
       build configurations you want to build. Then click on
       Build.
     * To run a specific test from Visual C++, go to
       Project+Settings.... There select that test's project and
       build configuration and go to the Debug tab. There type the
       name of the specific test to run (e.g. 'thread') in the
       Program arguments field. Validate your change by clicking
       on Ok and start the test by clicking the red exclamation
       mark (or hitting 'F5' or any other usual method).
     * You can also run the tests from the command line. You will
       find them in either Output\Win32_Wine_Headers or
       Output\Win32_MSVC_Headers depending on the build method. So
       to run the kernel 'path' tests you would do:

C:\>cd dlls\kernel\tests\Output\Win32_MSVC_Headers
C:\wine\dlls\kernel\tests\Output\Win32_MSVC_Headers> kernel32_test path
     __________________________________________________________

With MinGW

   Wine's build system already has support for building tests with
   a MinGW cross-compiler. See the section above called 'Setup of
   the MinGW cross-compiling environment' for instructions on how
   to set things up. When you have a MinGW environment installed
   all you need to do is rerun configure and it should detect the
   MinGW compiler and tools. Then run 'make crosstest' to start
   building the tests.
     __________________________________________________________

Standalone, using the Microsoft C++ Toolkit

   Sometimes it's nice to be able to build a new unit test on
   Windows without Wine, and without buying Microsoft Visual C++.
   Here's the simplest way to do that on a Windows system:

     * Download and install the free-as-in-beer Microsoft C++
       Toolkit and the Microsoft Platform SDK.
     * Make a directory wine underneath your work directory, and
       copy the file wine/test.h from the Wine source tree there.
       (You can download this file from the latest revision at
       http://source.winehq.org/git/?p=wine.git;a=blob_plain;f=inc
       lude/wine/test.h).
     * Copy some existing test from the Wine source tree, or
       create your test program (say, mytest.c) using Notepad,
       being sure to begin it with #include <wine/test.h>
       following the usual Wine test style.
     * Finally, in a command prompt window, compile the test with
       the command

C:\your\work\dir>cl -I. -DSTANDALONE -D_X86_ mytest.c

     * Once that's working, try running the program under Wine
       without recompiling it. See? No Wine source required at
       all, save for that one header, wine/test.h.
     * If you want to use the Microsoft C++ Toolkit under Wine,
       install it under Windows, then copy it to your fake C
       drive; it'll work fine there. See CL Howto for some tips on
       making it easy to use from the Linux commandline.
     __________________________________________________________

Inside a test

   When writing new checks you can either modify an existing test
   file or add a new one. If your tests are related to the tests
   performed by an existing file, then add them to that file.
   Otherwise create a new .c file in the tests directory and add
   that file to the CTESTS variable in Makefile.in.

   A new test file will look something like the following:
#include <wine/test.h>
#include <winbase.h>

/* Maybe auxiliary functions and definitions here */

START_TEST(paths)
{
   /* Write your checks there or put them in functions you will call fro
m
    * there
    */
}

   The test's entry point is the START_TEST section. This is where
   execution will start. You can put all your tests in that
   section but it may be better to split related checks in
   functions you will call from the START_TEST section. The
   parameter to START_TEST must match the name of the C file. So
   in the above example the C file would be called paths.c.

   Tests should start by including the wine/test.h header. This
   header will provide you access to all the testing framework
   functions. You can then include the windows header you need,
   but make sure to not include any Unix or Wine specific header:
   tests must compile on Windows.

   You can use trace to print informational messages. Note that
   these messages will only be printed if 'runtest -v' is being
   used.
  trace("testing GlobalAddAtomA\n");
  trace("foo=%d\n",foo);

   Then just call functions and use ok to make sure that they
   behaved as expected:
  ATOM atom = GlobalAddAtomA( "foobar" );
  ok( GlobalFindAtomA( "foobar" ) == atom, "could not find atom foobar\n
" );
  ok( GlobalFindAtomA( "FOOBAR" ) == atom, "could not find atom FOOBAR\n
" );

   The first parameter of ok is an expression which must evaluate
   to true if the test was successful. The next parameter is a
   printf-compatible format string which is displayed in case the
   test failed, and the following optional parameters depend on
   the format string.
     __________________________________________________________

Writing good error messages

   The message that is printed when a test fails is extremely
   important.

   Someone will take your test, run it on a Windows platform that
   you don't have access to, and discover that it fails. They will
   then post an email with the output of the test, and in
   particular your error message. Someone, maybe you, will then
   have to figure out from this error message why the test failed.

   If the error message contains all the relevant information that
   will be easy. If not, then it will require modifying the test,
   finding someone to compile it on Windows, sending the modified
   version to the original tester and waiting for his reply. In
   other words, it will be long and painful.

   So how do you write a good error message? Let's start with an
   example of a bad error message:
    ok(GetThreadPriorityBoost(curthread,&disabled)!=0,
       "GetThreadPriorityBoost Failed\n");

   This will yield:
   thread.c:123: Test failed: GetThreadPriorityBoost Failed

   Did you notice how the error message provides no information
   about why the test failed? We already know from the line number
   exactly which test failed. In fact the error message gives
   strictly no information that cannot already be obtained by
   reading the code. In other words it provides no more
   information than an empty string!

   Let's look at how to rewrite it:
    BOOL rc;
...
    rc=GetThreadPriorityBoost(curthread,&disabled);
    ok(rc!=0 && disabled==0,"rc=%d error=%ld disabled=%d\n",
       rc,GetLastError(),disabled);

   This will yield:
   thread.c:123: Test failed: rc=0 error=120 disabled=0

   When receiving such a message, one would check the source, see
   that it's a call to GetThreadPriorityBoost, that the test
   failed not because the API returned the wrong value, but
   because it returned an error code. Furthermore we see that
   GetLastError() returned 120 which winerror.h defines as
   ERROR_CALL_NOT_IMPLEMENTED. So the source of the problem is
   obvious: this Windows platform (here Windows 98) does not
   support this API and thus the test must be modified to detect
   such a condition and skip the test.

   So a good error message should provide all the information
   which cannot be obtained by reading the source, typically the
   function return value, error codes, and any function output
   parameter. Even if more information is needed to fully
   understand a problem, systematically providing the above is
   easy and will help cut down the number of iterations required
   to get to a resolution.

   It may also be a good idea to dump items that may be hard to
   retrieve from the source, like the expected value in a test if
   it is the result of an earlier computation, or comes from a
   large array of test values (e.g. index 112 of _pTestStrA in
   vartest.c). In that respect, for some tests you may want to
   define a macro such as the following:
#define eq(received, expected, label, type) \
        ok((received) == (expected), "%s: got " type " instead of " type
 "\n", (label),(received),(expected))

...

    eq( b, curr_val, "SPI_{GET,SET}BEEP", "%d" );
     __________________________________________________________

Handling platform issues

   Some checks may be written before they pass successfully in
   Wine. Without some mechanism, such checks would potentially
   generate hundred of known failures for months each time the
   tests are being run. This would make it hard to detect new
   failures caused by a regression. or to detect that a patch
   fixed a long standing issue.

   Thus the Wine testing framework has the concept of platforms
   and groups of checks can be declared as expected to fail on
   some of them. In the most common case, one would declare a
   group of tests as expected to fail in Wine. To do so, use the
   following construct:
todo_wine {
    SetLastError( 0xdeadbeef );
    ok( GlobalAddAtomA(0) == 0 && GetLastError() == 0xdeadbeef, "failed
to add atom 0\n" );
}

   On Windows the above check would be performed normally, but on
   Wine it would be expected to fail, and not cause the failure of
   the whole test. However. If that check were to succeed in Wine,
   it would cause the test to fail, thus making it easy to detect
   when something has changed that fixes a bug. Also note that
   todo checks are accounted separately from regular checks so
   that the testing statistics remain meaningful.

   When writing tests you will also encounter differences between
   Windows 9x and Windows NT platforms. Such differences should be
   treated differently from the platform issues mentioned above.
   In particular you should remember that the goal of Wine is not
   to be a clone of any specific Windows version but to run
   Windows applications on Unix.

   So, if an API returns a different error code on Windows 9x and
   Windows NT, your check should just verify that Wine returns one
   or the other:
 ok ( GetLastError() == WIN9X_ERROR || GetLastError() == NT_ERROR, ...);

   If an API is only present on some Windows platforms, then use
   LoadLibrary and GetProcAddress to check if it is implemented
   and invoke it. Remember, tests must run on all Windows
   platforms. Similarly, conformance tests should nor try to
   correlate the Windows version returned by GetVersion with
   whether given APIs are implemented or not. Again, the goal of
   Wine is to run Windows applications (which do not do such
   checks), and not be a clone of a specific Windows version.
     __________________________________________________________

Documenting Wine

   This chapter describes how you can help improve Wine's
   documentation.

   Like most large scale volunteer projects, Wine is strongest in
   areas that are rewarding for its volunteers to work in. The
   majority of contributors send code patches either fixing bugs,
   adding new functionality or otherwise improving the software
   components of the distribution. A lesser number contribute in
   other ways, such as reporting bugs and regressions, creating
   tests, providing organizational assistance, or helping to
   document Wine.

   Documentation is important for many reasons, and is often the
   key to the end user having a successful experience in
   installing, setting up and using software. Because Wine is a
   complicated, evolving entity, providing quality up to date
   documentation is vital to encourage more people to persevere
   with using and contributing to the project. The following
   sections describe in detail how to go about adding to or
   updating Wine's existing documentation.
     __________________________________________________________

An Overview Of Wine Documentation

   The Wine source code tree comes with a large amount of
   documentation in the documentation/ subdirectory. This used to
   be a collection of text files culled from various places such
   as the Wine Weekly News and the wine-devel mailing list, but
   was reorganized some time ago into a number of books, each of
   which is marked up using SGML. You are reading one of these
   books (the Wine Developer's Guide) right now.

   Since being reorganized, the books have been updated and
   extended regularly. In their current state they provide a good
   framework which over time can be expanded and kept up to date.
   This means that most of the time when further documentation is
   added, it is a simple matter of updating the content of an
   already existing file. The books available at the time of
   writing are:

     * The Wine User Guide. This book contains information for end
       users on installing, configuring and running Wine.
     * The Wine Developer's Guide. This book contains information
       and guidelines for developers and contributors to the Wine
       project.
     * The Winelib User's Guide. This book contains information
       for developers using Winelib to port Win32 applications to
       Unix.
     * The Wine Packager's Guide. This book contains information
       for anyone who will be distributing Wine to end users in a
       prepackaged format. It is also the exception to the rule as
       it has intentionally been kept in text format.
     * The Wine FAQ. This book contains frequently asked questions
       about Wine with their answers.

   To obtain a copy of the Wine documentation refer to the
   Documentation Git tree.

   Another source of documentation is the Wine API Guide. This is
   generated information taken from special comments placed in the
   Wine source code. When you update or add new API calls to Wine
   you should consider documenting them so that developers can
   determine what the API does and how it should be used.

   The next sections describe how to create Wine API documentation
   and how to work with SGML so you can add to the existing books.
     __________________________________________________________

Writing Wine API Documentation

Introduction to API Documentation

   Wine includes a large amount of documentation on the API
   functions it implements. There are several reasons to want to
   document the Win32 API:

     * To allow Wine developers to know what each function should
       do, should they need to update or fix it.
     * To allow Winelib users to understand the functions that are
       available to their applications.
     * To provide an alternative source of free documentation on
       the Win32 API.
     * To provide more accurate documentation where the existing
       documentation is accidentally or deliberately vague or
       misleading.

   To this end, a semi formalized way of producing documentation
   from the Wine source code has evolved. Since the primary users
   of API documentation are Wine developers themselves,
   documentation is usually inserted into the source code in the
   form of comments and notes. Good things to include in the
   documentation of a function include:

     * The purpose of the function.
     * The parameters of the function and their purpose.
     * The return value of the function, in success as well as
       failure cases.
     * Additional notes such as interaction with other parts of
       the system, differences between Wine's implementation and
       Win32s, errors in MSDN documentation, undocumented cases
       and bugs that Wine corrects or is compatible with.

   Good documentation helps developers be aware of the effects of
   making changes. It also allows good tests to be written which
   cover all of the documented cases.

   Note that you do not need to be a programmer to update the
   documentation in Wine. If you would like to contribute to the
   project, patches that improve the API documentation are
   welcome. The following describes how to format any
   documentation that you write so that the Wine documentation
   generator can extract it and make it available to other
   developers and users.

   In general, if you did not write the function in question, you
   should be wary of adding comments to other peoples code. It is
   quite possible you may misunderstand or misrepresent what the
   original author intended! Adding API documentation on the other
   hand can be done by anybody, since in most cases there is
   plenty of information about what a function is supposed to do
   (if it isn't obvious) available in books and articles on the
   internet.

   A final warning concerns copyright and must be noted. If you
   read MSDN or any publication in order to find out what an API
   call does, you must be aware that the text you are reading is
   copyrighted and in most cases cannot legally be reproduced
   without the authors permission. If you copy verbatim any
   information from such sources and submit it for inclusion into
   Wine, you open yourself up to potential legal liability. You
   must ensure that anything you submit is your own work, although
   it can be based on your understanding gleaned from reading
   other peoples work.
     __________________________________________________________

Basic API Documentation

   The general form of an API comment in Wine is a block comment
   immediately before a function is implemented in the source
   code. General comments within a function body or at the top of
   an implementation file are ignored by the API documentation
   generator. Such comments are for the benefit of developers
   only, for example to explain what the source code is doing or
   to describe something that may not be obvious to the person
   reading the source code.

   The following text uses the function PathRelativePathToA() from
   SHLWAPI.DLL as an example. You can find this function in the
   Wine source code tree in the file dlls/shlwapi/path.c.

   The first line of the comment gives the name of the function,
   the DLL that the function is exported from, and its export
   ordinal number. This is the simplest (and most common type of)
   comment:
/***********************************************************************
**
 * PathRelativePathToW   [SHLWAPI.@]
 */

   The functions name and the DLL name are obvious. The ordinal
   number takes one of two forms: Either @ as in the above, or a
   number if the export is exported by ordinal. You can see which
   to use by looking at the DLL's .spec file. If the line on which
   the function is listed begins with a number, use it, otherwise
   use the @ symbol, which indicates that this function is
   imported only by name.

   Note also that round or square brackets can be used, and
   whitespace between the name and the DLL/ordinal is free form.
   Thus the following is equally valid:
/***********************************************************************
**
 *              PathRelativePathToW     (SHLWAPI.@)
 */

   This basic comment will not get processed into documentation,
   since it contains no information. In order to produce
   documentation for the function, We must add some of the
   information listed above.

   First we add a description of the function. This can be as long
   as you like, but typically contains only a brief description of
   what the function is meant to do in general terms. It is free
   form text:
/***********************************************************************
**
 * PathRelativePathToW   [SHLWAPI.@]
 *
 * Create a relative path from one path to another.
 */

   To be truly useful however we must document the parameters to
   the function. There are two methods for doing this: In the
   comment, or in the function prototype.

   Parameters documented in the comment should be formatted as
   follows:
/***********************************************************************
**
 * PathRelativePathToW   [SHLWAPI.@]
 *
 * Create a relative path from one path to another.
 *
 * PARAMS
 *  lpszPath   [O] Destination for relative path
 *  lpszFrom   [I] Source path
 *  dwAttrFrom [I] File attribute of source path
 *  lpszTo     [I] Destination path
 *  dwAttrTo   [I] File attributes of destination path
 *
 */

   The parameters section starts with PARAMS on its own line. Each
   parameter is listed in the order they appear in the functions
   prototype, first with the parameters name, followed by its
   input/output status, followed by a free form text description
   of the comment.

   The input/output status tells the programmer whether the value
   will be modified by the function (an output parameter), or only
   read (an input parameter). The status must be enclosed in
   square brackets to be recognized, otherwise, or if it is
   absent, anything following the parameter name is treated as the
   parameter description. This field is case insensitive and can
   be any of the following: [I], [In], [O], [Out], [I/O],
   [In/Out].

   Following the description and parameters come a number of
   optional sections, all in the same format. A section is defined
   as the section name, which is an all upper case section name on
   its own line, followed by free form text. You can create any
   sections you like, however for consistency it is recommended
   you use the following section names:

    1. NOTES. Anything that needs to be noted about the function
       such as special cases and the effects of input arguments.
    2. BUGS. Any bugs in the function that exist 'by design', i.e.
       those that will not be fixed or exist for compatibility
       with Windows.
    3. TODO. Any unhandled cases or missing functionality in the
       Wine implementation of the function.
    4. FIXME. Things that should be updated or addressed in the
       implementation of the function at some future date (perhaps
       dependent on other parts of Wine). Note that if this
       information is only relevant to Wine developers then it
       should probably be placed in the relevant code section
       instead.

   Following or before the optional sections comes the RETURNS
   section which describes the return value of the function. This
   is free form text but should include what is returned on
   success as well as possible error return codes. Note that this
   section must be present for documentation to be generated for
   your comment.

   Our final documentation looks like the following:
/***********************************************************************
**
 * PathRelativePathToW   [SHLWAPI.@]
 *
 * Create a relative path from one path to another.
 *
 * PARAMS
 *  lpszPath   [O] Destination for relative path
 *  lpszFrom   [I] Source path
 *  dwAttrFrom [I] File attribute of source path
 *  lpszTo     [I] Destination path
 *  dwAttrTo   [I] File attributes of destination path
 *
 * RETURNS
 *  TRUE  If a relative path can be formed. lpszPath contains the new pa
th
 *  FALSE If the paths are not relative or any parameters are invalid
 *
 * NOTES
 *  lpszTo should be at least MAX_PATH in length.
 *  Calling this function with relative paths for lpszFrom or lpszTo may
 *  give erroneous results.
 *
 *  The Win32 version of this function contains a bug where the lpszTo s
tring
 *  may be referenced 1 byte beyond the end of the string. As a result r
andom
 *  garbage may be written to the output path, depending on what lies be
yond
 *  the last byte of the string. This bug occurs because of the behaviou
r of
 *  PathCommonPrefix() (see notes for that function), and no workaround
seems
 *  possible with Win32.
 *  This bug has been fixed here, so for example the relative path from
"\\"
 *  to "\\" is correctly determined as "." in this implementation.
 */
     __________________________________________________________

Advanced API Documentation

   There is no markup language for formatting API comments, since
   they should be easily readable by any developer working on the
   source file. A number of constructs are treated specially
   however, and are noted here. You can use these constructs to
   enhance the usefulness of the generated documentation by making
   it easier to read and referencing related documents.

   Any valid c identifier that ends with () is taken to be an API
   function and is formatted accordingly. When generating
   documentation, this text will become a link to that API call,
   if the output type supports hyperlinks or their equivalent.

   Similarly, any interface name starting with a capital I and
   followed by the words "reference" or "object" become a link to
   that objects documentation.

   Where an Ascii and Unicode version of a function are available,
   it is recommended that you document only the Unicode version
   and have the Ascii version refer to the Unicode one, as
   follows:
/***********************************************************************
**
 * PathRelativePathToA   [SHLWAPI.@]
 *
 * See PathRelativePathToW.
 */

   Alternately you may use the following form:
/***********************************************************************
**
 * PathRelativePathToA   [SHLWAPI.@]
 *
 * Unicode version of PathRelativePathToW.
 */

   You may also use this construct in any other section, such as
   NOTES.

   Any numbers and text in quotes ("") are highlighted.

   Words in all uppercase are assumed to be API constants and are
   highlighted. If you want to emphasize something in the
   documentation, put it in a section by itself rather than making
   it upper case.

   Blank lines in a section cause a new paragraph to be started.
   Blank lines at the start and end of sections are ignored.

   Any comment line starting with ("*|") is treated as raw text
   and is not pre-processed before being output. This should be
   used for code listings, tables and any text that should remain
   unformatted.

   Any line starting with a single word followed by a colon (:) is
   assumed to be case listing and is emphasized and put in its own
   paragraph. This is most often used for return values, as in the
   example section below.
 * RETURNS
 *  Success: TRUE. Something happens that is documented here.
 *  Failure: FALSE. The reasons why this call can fail are listed here.

   Any line starting with a (-) is put into a paragraph by itself.
   this allows lists to avoid being run together.

   If you are in doubt as to how your comment will look, try
   generating the API documentation and checking the output.
     __________________________________________________________

Extra API Documentation

   Simply documenting the API calls available provides a great
   deal of information to developers working with the Win32 API.
   However additional documentation is needed before the API Guide
   can be considered truly useful or comprehensive. For example,
   COM objects that are available for developers use should be
   documented, along with the interface(s) that those objects
   export. Also, it would be helpful to document each dll, to
   provide some structure to the documentation.

   To facilitate providing extra documentation, you can create
   comments that provide extra documentation on functions, or on
   keywords such as the name of a COM interface or a type
   definition.

   These items are generated using the same formatting rules as
   described earlier. The only difference is the first line of the
   comment, which indicates to the generator that the
   documentation is supplemental and does not describe an export
   from the dll being processed.

   Lets assume you have implemented a COM interface that you want
   to document; we'll use the name IExample as an example here.
   Your comment would look like the following (assuming you are
   exporting this object from EXAMPLE.DLL):
/***********************************************************************
**
 * IExample   {EXAMPLE}
 *
 * The IExample object provides lots of interesting functionality.
 * ...
 */

   Format this documentation exactly as you would a standard
   export. The only difference is the use of curly brackets to
   mark this documentation as supplemental. The generator will
   output this documentation using the name given before the DLL
   name, and will link to it from the main DLL page. In addition,
   if you have referred to the comment name in other documentation
   using "IExample interface", "IExample object", or "IExample()",
   those references will point to this documentation.

   If you document you COM interfaces this way then all following
   extra comments that follow in the same source file that begin
   with the same document title will be added as references to
   this comment before it is output. For an example of this see
   dlls/oleaut32/safearray.c. This uses an extra comment to
   document The SafeArray functions and link them together under
   one heading.

   As a special case, if you use the DLL name as the comment name,
   the comment will be treated as documentation on the DLL itself.
   When the documentation for the DLL is processed, the contents
   of the comment will be placed before the generated statistics,
   exports and other information that makes up a DLL's
   documentation page.
     __________________________________________________________

Generating API Documentation

   Having edited or added new API documentation to a source code
   file, you should generate the documentation to ensure that the
   result is what you expected. Wine includes a tool (slightly
   misleadingly) called c2man.pl in the tools/ directory which is
   used to generate the documentation from the source code.

   You can run c2man.pl manually for testing purposes; it is a
   fairly simple perl script which parses .c files to create
   output in several formats. If you wish to try this you may want
   to run it with no arguments, which will cause it to print usage
   information.

   An easier way is to use Wine's build system. To create man
   pages for a given dll, just type make man from within the dlls
   directory or type make manpages in the root directory of the
   Wine source tree. You can then check that a man page was
   generated for your function, it should be present in the
   documentation/man3w directory with the same name as the
   function.

   Once you have generated the man pages from the source code,
   running make install will install them for you. By default they
   are installed in section 3w of the manual, so they don't
   conflict with any existing man page names. So, to read the man
   page you should use man -S 3w {name}. Alternately you can edit
   /etc/man.config and add 3w to the list of search paths given in
   the variable MANSECT.

   You can also generate HTML output for the API documentation, in
   this case the make command is make doc-html in the dll
   directory, or make htmlpages from the root. The output will be
   placed by default under documentation/html. Similarly you can
   create SGML source code to produce the Wine Api Guide with the
   command make sgmlpages.
     __________________________________________________________

The Wine DocBook System

Writing Documentation with DocBook

   DocBook is a flavour of SGML (Standard Generalized Markup
   Language), a syntax for marking up the contents of documents.
   HTML is another very common flavour of SGML; DocBook markup
   looks very similar to HTML markup, although the names of the
   markup tags differ.
     __________________________________________________________

Getting Started

   Note Why SGML?


   The simple answer to that is that SGML allows you to create
   multiple formats of a given document from a single source.
   Currently it is used to create HTML, PDF, PS (PostScript) and
   Text versions of the Wine books.

   Note What do I need?


   You need the SGML tools. There are various places where you can
   get them. The most generic way of getting them is from their
   source as discussed below.

   Note Quick instructions


   These are the basic steps to create the Wine books from the
   SGML source.

    1. Go to http://www.sgmltools.org
    2. Download all of the sgmltools packages
    3. Install them all and build them (./configure; make; make
       install)
    4. Switch to your toplevel wine-docs directory
    5. Run ./configure
    6. run make html
    7. View en/wineusr-guide.html, en/winedev-guide.html, etc. in
       your favorite browser

   For more information on building the documentation, please see
   the README file at the toplevel wine-docs directory.
     __________________________________________________________

Getting SGML for various distributions

   Most Linux distributions have everything you need already
   bundled up in package form. Unfortunately, each distribution
   seems to handle its SGML environment differently, installing it
   into different paths, and naming its packages according to its
   own whims.
     __________________________________________________________

SGML on Red Hat

   The following packages seem to be sufficient for Red Hat 7.1.
   You will want to be careful about the order in which you
   install the RPMs.

     * sgml-common-*.rpm
     * openjade-*.rpm
     * perl-SGMLSpm-*.rpm
     * docbook-dtd*.rpm
     * docbook-style-dsssl-*.rpm
     * tetex-*.rpm
     * jadetex-*.rpm
     * docbook-utils-*.rpm

   You can also use ghostscript to view the ps format output and
   Adobe Acrobat 4 to view the pdf file.
     __________________________________________________________

SGML on Debian

   This is not a definitive list yet, but it seems you might need
   the following packages:

     * docbook
     * docbook-dsssl
     * docbook-utils
     * docbook-xml
     * docbook-xsl
     * sgml-base
     * sgml-data
     * tetex-base
     * tetex-bin
     * jade
     * jadetex
     __________________________________________________________

Terminology

   SGML markup contains a number of syntactical elements that
   serve different purposes in the markup. We'll run through the
   basics here to make sure we're on the same page when we refer
   to SGML semantics.

   The basic currency of SGML is the tag. A simple tag consists of
   a pair of angle brackets and the name of the tag. For example,
   the para tag would appear in an SGML document as <para>. This
   start tag indicates that the immediately following text should
   be classified according to the tag. In regular SGML, each
   opening tag must have a matching end tag to show where the
   start tag's contents end. End tags begin with "</" markup,
   e.g., </para>.

   The combination of a start tag, contents, and an end tag is
   called an element. SGML elements can be nested inside of each
   other, or contain only text, or may be a combination of both
   text and other elements, although in most cases it is better to
   limit your elements to one or the other.

   The XML (eXtensible Markup Language) specification, a modern
   subset of the SGML specification, adds a so-called empty tag,
   for elements that contain no text content. The entire element
   is a single tag, ending with "/>", e.g., <xref/>. However, use
   of this tag style restricts you to XML DocBook processing, and
   your document may no longer compile with SGML-only processing
   systems.

   Often a processing system will need more information about an
   element than you can provide with just tags. SGML allows you to
   add extra "hints" in the form of SGML attributes to pass along
   this information. The most common use of attributes in DocBook
   is giving specific elements a name, or an ID, so you can refer
   to it from elsewhere. This ID can be used for many things,
   including file-naming for HTML output, hyper-linking to
   specific parts of the document, and even pulling text from that
   element (see the <xref> tag).

   An SGML attribute appears inside the start tag, between the <
   and > brackets. For example, if you wanted to set the id
   attribute of the <book> element to "mybook", you would create a
   start tag like this:
   <book id="mybook">

   Notice that the contents of the attribute are enclosed in quote
   marks. These quotes are optional in SGML, but mandatory in XML.
   It's a good habit to use quotes, as it will make it much easier
   to migrate your documents to an XML processing system later on.

   You can also specify more than one attribute in a single tag:
   <book id="mybook" status="draft">

   Another commonly used type of SGML markup is the entity. An
   entity lets you associate a block of text with a name. You
   declare the entity once, at the beginning of your document, and
   can invoke it as many times as you like throughout the
   document. You can use entities as shorthand, or to make it
   easier to maintain certain phrases in a central location, or
   even to insert the contents of an entire file into your
   document.

   An entity in your document is always surrounded by the "&" and
   ";" characters. One entity you'll need sooner or later is the
   one for the "<" character. Since SGML expects all tags to begin
   with a "<", the "<" is a reserved character. To use it in your
   document (as I am doing here), you must insert it with the &lt;
   entity. Each time the SGML processor encounters &lt;, it will
   place a literal "<" in the output document. Similarly you must
   use the &gt; and &amp; entities for the ">" and "&" characters.

   The final term you'll need to know when writing simple DocBook
   documents is the DTD (Document Type Declaration). The DTD
   defines the flavour of SGML a given document is written in. It
   lists all the legal tag names, like <book>, <para>, and so on,
   and declares how those tags are allowed to be used together.
   For example, it doesn't make sense to put a <book> element
   inside a <para> paragraph element -- only the reverse makes
   sense.

   The DTD thus defines the legal structure of the document. It
   also declares which attributes can be used with which tags. The
   SGML processing system can use the DTD to make sure the
   document is laid out properly before attempting to process it.
   SGML-aware text editors like Emacs can also use the DTD to
   guide you while you write, offering you choices about which
   tags you can add in different places in the document, and
   beeping at you when you try to add a tag where it doesn't
   belong.

   Generally, you will declare which DTD you want to use as the
   first line of your SGML document. In the case of DocBook, you
   will use something like this:
<!doctype book PUBLIC "-//OASIS//DTD
            DocBook V3.1//EN" []> <book> ...
            </book>

   Note that you must specify your toplevel element inside the
   doctype declaration. If you were writing an article rather than
   a book, you might use this declaration instead:
<!doctype article PUBLIC "-//OASIS//DTD DocBook V3.1//EN" []>
<article>
...
</article>
     __________________________________________________________

The Document

   Once you're comfortable with SGML, creating a DocBook document
   is quite simple and straightforward. Even though DocBook
   contains over 300 different tags, you can usually get by with
   only a small subset of those tags. Most of them are for inline
   formatting, rather than for document structuring. Furthermore,
   the common tags have short, intuitive names.

   Below is a (completely nonsensical) example to illustrate how a
   simple document might be laid out. Notice that all <chapter>
   and <sect1> elements have id attributes. This is not mandatory,
   but is a good habit to get into, as DocBook is commonly
   converted into HTML, with a separate generated file for each
   <book>, <chapter>, and/or <sect1> element. If the given element
   has an id attribute, the processor will typically name the file
   accordingly. Thus, the below document might result in
   index.html, chapter-one.html, blobs.html, and so on.

   Also notice the text marked off with "<!-- " and " -->"
   characters. These denote SGML comments. SGML processors will
   completely ignore anything between these markers, similar to
   "/*" and "*/" comments in C source code.
<!doctype book PUBLIC "-//OASIS//DTD DocBook V3.1//EN" []>
<book id="index">
  <bookinfo>
    <title>A Poet's Guide to Nonsense</title>
  </bookinfo>

  <chapter id="chapter-one">
    <title>Blobs and Gribbles</title>

    <!-- This section contains only one major topic -->
    <sect1 id="blobs">
      <title>The Story Behind Blobs</title>
      <para>
        Blobs are often mistaken for ice cubes and rain
        puddles...
      </para>
    </sect1>

    <!-- This section contains embedded sub-sections -->
    <sect1 id="gribbles">
      <title>Your Friend the Gribble</title>
      <para>
        A Gribble is a cute, unassuming little fellow...
      </para>

      <sect2 id="gribble-temperament">
        <title>Gribble Temperament</title>
        <para>
          When left without food for several days...
        </para>
      </sect2>

      <sect2 id="gribble-appearance">
        <title>Gribble Appearance</title>
        <para>
          Most Gribbles have a shock of white fur running from...
        </para>
      </sect2>
    </sect1>
  </chapter>

  <chapter id="chapter-two">
    <title>Phantasmagoria</title>

    <sect1 id="dretch-pools">
      <title>Dretch Pools</title>

      <para>
        When most poets think of Dretch Pools, they tend to...
      </para>
    </sect>
  </chapter>
</book>
     __________________________________________________________

Common Elements

   Once you get used to the syntax of SGML, the next hurdle in
   writing DocBook documentation is to learn the many
   DocBook-specific tag names, and when to use them. DocBook was
   created for technical documentation, and as such, the tag names
   and document structure are slanted towards the needs of such
   documentation.

   To cover its target audience, DocBook declares a wide variety
   of specialized tags, including tags for formatting source code
   (with somewhat of a C/C++ bias), computer prompts, GUI
   application features, keystrokes, and so on. DocBook also
   includes tags for universal formatting needs, like headers,
   footnotes, tables, and graphics.

   We won't cover all of these elements here (over 300 DocBook
   tags exist!), but we will cover the basics. To learn more about
   the other tags, check out the official DocBook guide, at
   http://docbook.org. To see how they are used in practice,
   download the SGML source for this manual (the Wine Developer
   Guide) and browse through it, comparing it to the generated
   HTML (or PostScript or PDF).

   There are often many correct ways to mark up a given piece of
   text, and you may have to make guesses about which tag to use.
   Sometimes you'll have to make compromises. However, remember
   that it is possible to further customize the output of the SGML
   processors. If you don't like the way a certain tag looks in
   HTML, that doesn't mean you should choose a different tag based
   on its output formatting. The processing stylesheets can be
   altered to fix the formatting of that same tag everywhere in
   the document (not just in the place you're working on). For
   example, if you're frustrated that the <systemitem> tag doesn't
   produce any formatting by default, you should fix the
   stylesheets, not change the valid <systemitem> tag to, for
   example, an <emphasis> tag.

   Here are the common SGML elements:

   Structural Elements

   <book>
          The book is the most common toplevel element, and is
          probably the one you should use for your document.

   <set>
          If you want to group more than one book into a single
          unit, you can place them all inside a set. This is
          useful when you want to bundle up documentation in
          alternate ways. We do this with the Wine documentation,
          using <book> to put each Wine guide into a separate
          directory (see documentation/wine-devel.sgml, etc.).

   <chapter>
          A <chapter> element includes a single entire chapter of
          the book.

   <part>
          If the chapters in your book fall into major categories
          or groupings (as in the Wine Developer Guide), you can
          place each collection of chapters into a <part> element.

   <sect?>
          DocBook has many section elements to divide the contents
          of a chapter into smaller chunks. The encouraged
          approach is to use the numbered section tags, <sect1>,
          <sect2>, <sect3>, <sect4>, and <sect5> (if necessary).
          These tags must be nested in order: you can't place a
          <sect3> directly inside a <sect1>. You have to nest the
          <sect3> inside a <sect2>, and so forth. Documents with
          these explicit section groupings are easier for SGML
          processors to deal with, and lead to better organized
          documents. DocBook also supplies a <section> element
          which you can nest inside itself, but its use is
          discouraged in favor of the numbered section tags.

   <title>
          The title of a book, chapter, part, section, etc. In
          most of the major structural elements, like <chapter>,
          <part>, and the various section tags, <title> is
          mandatory. In other elements like <book> and <note>,
          it's optional.

   <para>
          The basic unit of text is the paragraph, represented by
          the <para> tag. This is probably the tag you'll use most
          often. In fact, in a simple document, you can probably
          get away with using only <book>, <chapter>, <title>, and
          <para>.

   <article>
          For shorter, more targeted documents, like topic pieces
          and whitepapers, you can use <article> as your toplevel
          element.

   Inline Formatting Elements

   <filename>
          The name of a file. You can optionally set the class
          attribute to Directory, HeaderFile, and SymLink to
          further classify the filename.

   <userinput>
          Literal text entered by the user.

   <computeroutput>
          Literal text output by the computer.

   <literal>
          A catch-all element for literal computer data. Its use
          is somewhat vague; try to use a more specific tag if
          possible, like <userinput> or <computeroutput>.

   <quote>
          An inline quotation. This tag typically inserts
          quotation marks for you, so you would write <quote>This
          is a quote</quote> rather than "This is a quote". This
          usage may be a little bulkier, but it does allow for
          automated formatting of all quoted material in the
          document. Thus, if you wanted all quotations to appear
          in italic, you could make the change once in your
          stylesheet, rather than doing a search and replace
          throughout the document. For larger chunks of quoted
          text, you can use <blockquote>.

   <note>
          Insert a side note for the reader. By default, the SGML
          processor usually prefixes the content with "Note:". You
          can change this text by adding a <title> element. Thus,
          to add a visible FIXME comment to the documentation, you
          might write:

<note>
  <title>EXAMPLE</title>
  <para>This is an example note...</para>
</note>

          The results will look something like this:

          Note EXAMPLE


   This is an example note...

   <sgmltag>
          Used for inserting SGML tags, etc., into a SGML document
          without resorting to a lot of entity quoting, e.g.,
          &lt;. You can change the appearance of the text with the
          class attribute. Some common values of this are
          starttag, endtag, attribute, attvalue, and even
          sgmlcomment. See this SGML file,
          documentation/documentation.sgml, for examples.

   <prompt>
          The text used for a computer prompt, for example a shell
          prompt, or command-line application prompt.

   <replaceable>
          Meta-text that should be replaced by the user, not typed
          in literally, e.g., in command descriptions and --help
          outputs.

   <constant>
          A programming constant, e.g., MAX_PATH.

   <symbol>
          A symbolic value replaced, for example, by a
          pre-processor. This applies primarily to C macros, but
          may have other uses. Use the <constant> tag instead of
          <symbol> where appropriate.

   <function>
          A programming function name.

   <parameter>
          Programming language parameters you pass with a
          function.

   <option>
          Parameters you pass to a command-line executable.

   <varname>
          Variable name, typically in a programming language.

   <type>
          Programming language types, e.g., from a typedef
          definition. May have other uses, too.

   <structname>
          The name of a C-language struct declaration, e.g.,
          sockaddr.

   <structfield>
          A field inside a C struct.

   <command>
          An executable binary, e.g., wine or ls.

   <envar>
          An environment variable, e.g, $PATH.

   <systemitem>
          A generic catch-all for system-related things, like OS
          names, computer names, system resources, etc.

   <email>
          An email address. The SGML processor will typically add
          extra formatting characters, and even a mailto: link for
          HTML pages. Usage: <email>user@host.com</email>

   <firstterm>
          Special emphasis for introducing a new term. Can also be
          linked to a <glossary> entry, if desired.

   Item Listing Elements

   <itemizedlist>
          For bulleted lists, no numbering. You can tweak the
          layout with SGML attributes.

   <orderedlist>
          A numbered list; the SGML processor will insert the
          numbers for you. You can suggest numbering styles with
          the numeration attribute.

   <simplelist>
          A very simple list of items, often inlined. Control the
          layout with the type attribute.

   <variablelist>
          A list of terms with definitions or descriptions, like
          this very list!

   Block Text Quoting Elements

   <programlisting>
          Quote a block of source code. Typically highlighted in
          the output and set off from normal text.

   <screen>
          Quote a block of visible computer output, like the
          output of a command or chunks of debug logs.

   Hyperlink Elements

   <link>
          Generic hypertext link, used for pointing to other
          sections within the current document. You supply the
          visible text for the link, plus the name of the id
          attribute of the element that you want to link to. For
          example:

<link linkend="configuring-wine">the section on configuring wine</link>
...
<sect2 id="configuring-wine">
...

   <xref>
          In-document hyperlink that can generate its own text.
          Similar to the <link> tag, you use the linkend attribute
          to specify which target element you want to jump to:

<xref linkend="configuring-wine">
...
<sect2 id="configuring-wine">
...

          By default, most SGML processors will auto generate some
          generic text for the <xref> link, like "Section 2.3.1".
          You can use the endterm attribute to grab the visible
          text content of the hyperlink from another element:

<xref linkend="configuring-wine" endterm="config-title">
...
<sect2 id="configuring-wine">
  <title id="config-title">Configuring Wine</title>
...

          This would create a link to the configuring-wine
          element, displaying the text of the config-title element
          for the hyperlink. Most often, you'll add an id
          attribute to the <title> of the section you're linking
          to, as above, in which case the SGML processor will use
          the target's title text for the link text.

          Alternatively, you can use an xreflabel attribute in the
          target element tag to specify the link text:

<sect1 id="configuring-wine" xreflabel="Configuring Wine">

   Note

   <xref> is an empty element. You don't need a closing tag for it
   (this is defined in the DTD). In SGML documents, you should use
   the form <xref>, while in XML documents you should use <xref/>.

   <anchor>
          An invisible tag, used for inserting id attributes into
          a document to link to arbitrary places (i.e., when it's
          not close enough to link to the top of an element).

   <ulink>
          Hyperlink in URL form, e.g., http://www.winehq.org.

   <olink>
          Indirect hyperlink; can be used for linking to external
          documents. Not often used in practice.
     __________________________________________________________

Editing SGML Documents

   You can write SGML/DocBook documents in any text editor you
   might find although some editors are more friendly for this
   task than others.

   The most commonly used open source SGML editor is Emacs, with
   the PSGML mode, or extension. Emacs does not supply a GUI or
   WYSIWYG (What You See Is What You Get) interface, but it does
   provide many helpful shortcuts for creating SGML, as well as
   automatic formatting, validity checking, and the ability to
   create your own macros to simplify complex, repetitive actions.

II. Wine Architecture

   Table of Contents
   Overview
   Kernel modules
   Graphical modules
   Windowing system
   COM in Wine
   Wine and OpenGL
   Outline of DirectDraw Architecture
   Wine and Multimedia
     __________________________________________________________

Overview

   Brief overview of Wine's architecture...
     __________________________________________________________

Wine Overview

Foreword

   Wine is often used as a recursive acronym, standing for "Wine
   Is Not an Emulator". Sometimes it is also known to be used for
   "Windows Emulator". In a way, both meanings are correct, only
   seen from different perspectives. The first meaning says that
   Wine is not a virtual machine, it does not emulate a CPU, and
   you are not supposed to install Windows nor any Windows device
   drivers on top of it; rather, Wine is an implementation of the
   Windows API, and can be used as a library to port Windows
   applications to Unix. The second meaning, obviously, is that to
   Windows binaries (.exe files), Wine does look like Windows, and
   emulates its behaviour and quirks rather closely.

   Note "Emulator"


   The "Emulator" perspective should not be thought of as if Wine
   is a typical inefficient emulation layer that means Wine can't
   be anything but slow - the faithfulness to the badly designed
   Windows API may of course impose a minor overhead in some
   cases, but this is both balanced out by the higher efficiency
   of the Unix platforms Wine runs on, and that other possible
   abstraction libraries (like Motif, GTK+, CORBA, etc) has a
   runtime overhead typically comparable to Wine's.
     __________________________________________________________

Executables

   Wine's main task is to run Windows executables under non
   Windows operating systems. It supports different types of
   executables:

     * DOS executable. Those are even older programs, using the
       DOS format (either .com or .exe (the later being also
       called MZ)).
     * Windows NE executable, also called 16 bit. They were the
       native processes run by Windows 2.x and 3.x. NE stands for
       New Executable <g>.
     * Windows PE executable. These are programs were introduced
       in Windows 95 (and became the native formats for all later
       Windows version), even if 16 bit applications were still
       supported. PE stands for Portable Executable, in a sense
       where the format of the executable (as a file) is
       independent of the CPU (even if the content of the file -
       the code - is CPU dependent).
     * Winelib executable. These are applications, written using
       the Windows API, but compiled as a Unix executable. Wine
       provides the tools to create such executables.

   Let's quickly review the main differences for the supported
   executables:

   Table 1. Wine executables
     DOS (.COM or .EXE) Win16 (NE) Win32 (PE) Win64 (PE) Winelib
   Multitasking Only one application at a time (except for TSR)
   Cooperative Preemptive Preemptive Preemptive
   Address space One MB of memory, where each application is
   loaded and unloaded. All 16 bit applications share a single
   address space, protected mode. Each application has it's own
   address space. Requires MMU support from CPU. Each application
   has it's own address space. Requires MMU support from CPU. Each
   application has it's own address space. Requires MMU support
   from CPU.
   Windows API No Windows API but the DOS API (like Int 21h
   traps). Will call the 16 bit Windows API. Will call the 32 bit
   Windows API. Will call the 64 bit Windows API. Will call the
   32/64 bit Windows API, and possibly also the Unix APIs.
   Code (CPU level) Only available on x86 in real mode. Code and
   data are in segmented forms, with 16 bit offsets. Processor is
   in real mode. Only available on IA-32 architectures, code and
   data are in segmented forms, with 16 bit offsets (hence the 16
   bit name). Processor is in protected mode. Available (with NT)
   on several CPUs, including IA-32. On this CPU, uses a flat
   memory model with 32 bit offsets (hence the 32 bit name). Only
   available on AMD64 architectures. Flat model, with 32/64 bit
   addresses.
   Multi-threading Not available. Not available. Available.
   Available. Available, but must use the Win32/64 APIs for
   threading and synchronization, not the Unix ones.

   Wine deals with this issue by launching a separate Wine process
   (which is in fact a Unix process) for each Win32 process, but
   not for Win16 tasks. Win16 tasks are run as different
   intersynchronized Unix-threads in the same dedicated Wine
   process; this Wine process is commonly known as a WOW process
   (Windows on Windows), referring to a similar mechanism used by
   Windows NT.

   Synchronization between the Win16 tasks running in the WOW
   process is normally done through the Win16 mutex - whenever one
   of them is running, it holds the Win16 mutex, keeping the
   others from running. When the task wishes to let the other
   tasks run, the thread releases the Win16 mutex, and one of the
   waiting threads will then acquire it and let its task run.

   winevdm is the Wine process dedicated to running the Win16
   processes. Note that several instances of this process could
   exist, as Windows has support for different VDM (Virtual Dos
   Machines) in order to have Win16 processes running in different
   address spaces. Wine also uses the same architecture to run DOS
   programs (in this case, the DOS emulation is provided by a Wine
   only DLL called winedos.
     __________________________________________________________

Standard Windows Architectures

Windows 9x architecture

   The windows architecture (Win 9x way) looks like this:
+---------------------+        \
|     Windows EXE     |         } application
+---------------------+        /

+---------+ +---------+        \
| Windows | | Windows |         \ application & system DLLs
|   DLL   | |   DLL   |         /
+---------+ +---------+        /

+---------+ +---------+      \
|  GDI32  | | USER32  |       \
|   DLL   | |   DLL   |        \
+---------+ +---------+         } core system DLLs
+---------------------+        /
|     Kernel32 DLL    |       /
+---------------------+      /

+---------------------+        \
|     Win9x kernel    |         } kernel space
+---------------------+        /

+---------------------+       \
|  Windows low-level  |        \ drivers (kernel space)
|       drivers       |        /
+---------------------+       /
     __________________________________________________________

Windows NT architecture

   The windows architecture (Windows NT way) looks like the
   following drawing. Note the new DLL (NTDLL) which allows
   implementing different subsystems (as win32); kernel32 in NT
   architecture implements the Win32 subsystem on top of NTDLL.
+---------------------+                      \
|     Windows EXE     |                       } application
+---------------------+                      /

+---------+ +---------+                      \
| Windows | | Windows |                       \ application & system DLL
s
|   DLL   | |   DLL   |                       /
+---------+ +---------+                      /

+---------+ +---------+     +-----------+   \
|  GDI32  | |  USER32 |     |           |    \
|   DLL   | |   DLL   |     |           |     \
+---------+ +---------+     |           |      \ core system DLLs
+---------------------+     |           |      / (on the left side)
|    Kernel32 DLL     |     | Subsystem |     /
|  (Win32 subsystem)  |     |Posix, OS/2|    /
+---------------------+     +-----------+   /

+---------------------------------------+
|               NTDLL.DLL               |
+---------------------------------------+

+---------------------------------------+     \
|               NT kernel               |      } NT kernel (kernel space
)
+---------------------------------------+     /
+---------------------------------------+     \
|       Windows low-level drivers       |      } drivers (kernel space)
+---------------------------------------+     /

   Note also (not depicted in schema above) that the 16 bit
   applications are supported in a specific subsystem. Some basic
   differences between the Win9x and the NT architectures include:

     * Several subsystems (Win32, Posix...) can be run on NT,
       while not on Win 9x
     * Win 9x roots its architecture in 16 bit systems, while NT
       is truly a 32 bit system.
     * The drivers model and interfaces in Win 9x and NT are
       different (even if Microsoft tried to bridge the gap with
       some support of WDM drivers in Win 98 and above).
     __________________________________________________________

Wine architecture

Global picture

   Wine implementation is closer to the Windows NT architecture,
   even if several subsystems are not implemented yet (remind also
   that 16bit support is implemented in a 32-bit Windows EXE, not
   as a subsystem). Here's the overall picture:
+---------------------+                                  \
|     Windows EXE     |                                   } application
+---------------------+                                  /

+---------+ +---------+                                  \
| Windows | | Windows |                                   \ application
& system DLLs
|   DLL   | |   DLL   |                                   /
+---------+ +---------+                                  /

+---------+ +---------+     +-----------+  +--------+  \
|  GDI32  | |  USER32 |     |           |  |        |   \
|   DLL   | |   DLL   |     |           |  |  Wine  |    \
+---------+ +---------+     |           |  | Server |     \ core system
DLLs
+---------------------+     |           |  |        |     / (on the left
 side)
|    Kernel32 DLL     |     | Subsystem |  | NT-like|    /
|  (Win32 subsystem)  |     |Posix, OS/2|  | Kernel |   /
+---------------------+     +-----------+  |        |  /
                                           |        |
+---------------------------------------+  |        |
|                 NTDLL                 |  |        |
+---------------------------------------+  +--------+

+---------------------------------------+               \
|   Wine executable (wine-?thread)      |                } unix executab
le
+---------------------------------------+               /
+---------------------------------------------------+   \
|                   Wine drivers                    |    } Wine specific
 DLLs
+---------------------------------------------------+   /

+------------+    +------------+     +--------------+   \
|    libc    |    |   libX11   |     |  other libs  |    } unix shared l
ibraries
+------------+    +------------+     +--------------+   /  (user space)

+---------------------------------------------------+   \
|         Unix kernel (Linux,*BSD,Solaris,OS/X)     |    } (Unix) kernel
 space
+---------------------------------------------------+   /
+---------------------------------------------------+   \
|                 Unix device drivers               |    } Unix drivers
(kernel space)
+---------------------------------------------------+   /

   Wine must at least completely replace the "Big Three" DLLs
   (KERNEL/KERNEL32, GDI/GDI32, and USER/USER32), which all other
   DLLs are layered on top of. But since Wine is (for various
   reasons) leaning towards the NT way of implementing things, the
   NTDLL is another core DLL to be implemented in Wine, and many
   KERNEL32 and ADVAPI32 features will be implemented through the
   NTDLL.

   As of today, no real subsystem (apart the Win32 one) has been
   implemented in Wine.

   The Wine server provides the backbone for the implementation of
   the core DLLs. It mainly implementents inter-process
   synchronization and object sharing. It can be seen, from a
   functional point of view, as a NT kernel (even if the APIs and
   protocols used between Wine's DLL and the Wine server are Wine
   specific).

   Wine uses the Unix drivers to access the various hardware
   pieces on the box. However, in some cases, Wine will provide a
   driver (in Windows sense) to a physical hardware device. This
   driver will be a proxy to the Unix driver (this is the case,
   for example, for the graphical part with X11 or SDL drivers,
   audio with OSS or ALSA drivers...).

   All DLLs provided by Wine try to stick as much as possible to
   the exported APIs from the Windows platforms. There are rare
   cases where this is not the case, and have been propertly
   documented (Wine DLLs export some Wine specific APIs). Usually,
   those are prefixed with __wine.

   Let's now review in greater details all of those components.
     __________________________________________________________

The Wine server

   The Wine server is among the most confusing concepts in Wine.
   What is its function in Wine? Well, to be brief, it provides
   Inter-Process Communication (IPC), synchronization, and
   process/thread management. When the Wine server launches, it
   creates a Unix socket for the current host based on (see below)
   your home directory's .wine subdirectory (or wherever the
   WINEPREFIX environment variable points to) - all Wine processes
   launched later connects to the Wine server using this socket.
   If a Wine server was not already running, the first Wine
   process will start up the Wine server in auto-terminate mode
   (i.e. the Wine server will then terminate itself once the last
   Wine process has terminated).

   In earlier versions of Wine the master socket mentioned above
   was actually created in the configuration directory; either
   your home directory's /wine subdirectory or wherever the
   WINEPREFIX environment variable points>. Since that might not
   be possible the socket is actually created within the /tmp
   directory with a name that reflects the configuration
   directory. This means that there can actually be several
   separate copies of the Wine server running; one per combination
   of user and configuration directory. Note that you should not
   have several users using the same configuration directory at
   the same time; they will have different copies of the Wine
   server running and this could well lead to problems with the
   registry information that they are sharing.

   Every thread in each Wine process has its own request buffer,
   which is shared with the Wine server. When a thread needs to
   synchronize or communicate with any other thread or process, it
   fills out its request buffer, then writes a command code
   through the socket. The Wine server handles the command as
   appropriate, while the client thread waits for a reply. In some
   cases, like with the various WaitFor??? synchronization
   primitives, the server handles it by marking the client thread
   as waiting and does not send it a reply before the wait
   condition has been satisfied.

   The Wine server itself is a single and separate Unix process
   and does not have its own threading - instead, it is built on
   top of a large poll() loop that alerts the Wine server whenever
   anything happens, such as a client having sent a command, or a
   wait condition having been satisfied. There is thus no danger
   of race conditions inside the Wine server itself - it is often
   called upon to do operations that look completely atomic to its
   clients.

   Because the Wine server needs to manage processes, threads,
   shared handles, synchronization, and any related issues, all
   the clients' Win32 objects are also managed by the Wine server,
   and the clients must send requests to the Wine server whenever
   they need to know any Win32 object handle's associated Unix
   file descriptor (in which case the Wine server duplicates the
   file descriptor, transmits it back to the client, and leaves it
   to the client to close the duplicate when the client has
   finished with it).
     __________________________________________________________

Wine builtin DLLs: about Relays, Thunks, and DLL descriptors

   This section mainly applies to builtin DLLs (DLLs provided by
   Wine). See section the Section called Wine/Windows DLLs for the
   details on native vs. builtin DLL handling.

   Loading a Windows binary into memory isn't that hard by itself,
   the hard part is all those various DLLs and entry points it
   imports and expects to be there and function as expected; this
   is, obviously, what the entire Wine implementation is all
   about. Wine contains a range of DLL implementations. You can
   find the DLLs implementation in the dlls/ directory.

   Each DLL (at least, the 32 bit version, see below) is
   implemented in a Unix shared library. The file name of this
   shared library is the module name of the DLL with a .dll.so
   suffix (or .drv.so or any other relevant extension depending on
   the DLL type). This shared library contains the code itself for
   the DLL, as well as some more information, as the DLL resources
   and a Wine specific DLL descriptor.

   The DLL descriptor, when the DLL is instanciated, is used to
   create an in-memory PE header, which will provide access to
   various information about the DLL, including but not limited to
   its entry point, its resources, its sections, its debug
   information...

   The DLL descriptor and entry point table is generated by the
   winebuild tool (previously just named build), taking DLL
   specification files with the extension .spec as input.
   Resources (after compilation by wrc) or message tables (after
   compilation by wmc) are also added to the descriptor by
   winebuild.

   Once an application module wants to import a DLL, Wine will
   look:

     * through its list of registered DLLs (in fact, both the
       already loaded DLLs, and the already loaded shared
       libraries which has registered a DLL descriptor). Since,
       the DLL descriptor is automatically registered when the
       shared library is loaded - remember, registration call is
       put inside a shared library constructor.
     * If it's not registered, Wine will look for it on disk,
       building the shared library name from the DLL module name.
       Directory searched for are specified by the WINEDLLPATH
       environment variable.
     * Failing that, it will look for a real Windows .DLL file to
       use, and look through its imports, etc) and use the loading
       of native DLLs.

   After the DLL has been identified (assuming it's still a native
   one), it's mapped into memory using a dlopen() call. Note, that
   Wine doesn't use the shared library mechanisms for resolving
   and/or importing functions between two shared libraries (for
   two DLLs). The shared library is only used for providing a way
   to load a piece of code on demand. This piece of code, thanks
   the DLL descriptor, will provide the same type of information a
   native DLL would. Wine can then use the same code for native
   and builtin DLL to handle imports/exports.

   Wine also relies on the dynamic loading features of the Unix
   shared libraries to relocate the DLLs if needed (the same DLL
   can be loaded at different address in two different processes,
   and even in two consecutive run of the same executable if the
   order of loading the DLLs differ).

   The DLL descriptor is registered in the Wine realm using some
   tricks. The winebuild tool, while creating the code for DLL
   descriptor, also creates a constructor, that will be called
   when the shared library is loaded into memory. This constructor
   will actually register the descriptor to the Wine DLL loader.
   Hence, before the dlopen call returns, the DLL descriptor will
   be known and registered. This also helps to deal with the cases
   where there's still dependencies (at the ELF shared lib level,
   not at the embedded DLL level) between different shared
   libraries: the embedded DLLs will be properly registered, and
   even loaded (from a Windows point of view).

   Since Wine is 32-bit code itself, and if the compiler supports
   Windows' calling convention, stdcall (gcc does), Wine can
   resolve imports into Win32 code by substituting the addresses
   of the Wine handlers directly without any thunking layer in
   between. This eliminates the overhead most people associate
   with "emulation", and is what the applications expect anyway.

   However, if the user specified WINEDEBUG=+relay , a thunk layer
   is inserted between the application imports and the Wine
   handlers (actually the export table of the DLL is modified, and
   a thunk is inserted in the table); this layer is known as
   "relay" because all it does is print out the arguments/return
   values (by using the argument lists in the DLL descriptor's
   entry point table), then pass the call on, but it's invaluable
   for debugging misbehaving calls into Wine code. A similar
   mechanism also exists between Windows DLLs - Wine can
   optionally insert thunk layers between them, by using
   WINEDEBUG=+snoop, but since no DLL descriptor information
   exists for non-Wine DLLs, this is less reliable and may lead to
   crashes.

   For Win16 code, there is no way around thunking - Wine needs to
   relay between 16-bit and 32-bit code. These thunks switch
   between the app's 16-bit stack and Wine's 32-bit stack, copies
   and converts arguments as appropriate (an int is 16 bit 16-bit
   and 32 bits in 32-bit, pointers are segmented in 16 bit (and
   also near or far) but are 32 bit linear values in 32 bit), and
   handles the Win16 mutex. Some finer control can be obtained on
   the conversion, see winebuild reference manual for the details.
   Suffice to say that the kind of intricate stack content
   juggling this results in, is not exactly suitable study
   material for beginners.

   A DLL descriptor is also created for every 16 bit DLL. However,
   this DLL normally paired with a 32 bit DLL. Either, it's the 16
   bit counterpart of the 16 bit DLL (KRNL386.EXE for KERNEL32,
   USER for USER32...), or a 16 bit DLL directly linked to a 32
   bit DLL (like SYSTEM for KERNEL32, or DDEML for USER32). In
   those cases, the 16 bit descriptor(s) is (are) inserted in the
   same shared library as the the corresponding 32 bit DLL. Wine
   will also create symbolic links between kernel32.dll.so and
   system.dll.so so that loading of either KERNEL32.DLL or
   SYSTEM.DLL will end up on the same shared library.
     __________________________________________________________

Wine/Windows DLLs

   This document mainly deals with the status of current DLL
   support by Wine. Winecfg currently supports settings to change
   the load order of DLLs. The load order depends on several
   issues, which results in different settings for various DLLs.
     __________________________________________________________

Pros of Native DLLs

   Native DLLs of course guarantee 100% compatibility for routines
   they implement. For example, using the native USER DLL would
   maintain a virtually perfect and Windows 95-like look for
   window borders, dialog controls, and so on. Using the built-in
   Wine version of this library, on the other hand, would produce
   a display that does not precisely mimic that of Windows 95.
   Such subtle differences can be engendered in other important
   DLLs, such as the common controls library COMMCTRL or the
   common dialogs library COMMDLG, when built-in Wine DLLs outrank
   other types in load order.

   More significant, less aesthetically-oriented problems can
   result if the built-in Wine version of the SHELL DLL is loaded
   before the native version of this library. SHELL contains
   routines such as those used by installer utilities to create
   desktop shortcuts. Some installers might fail when using Wine's
   built-in SHELL.
     __________________________________________________________

Cons of Native DLLs

   Not every application performs better under native DLLs. If a
   library tries to access features of the rest of the system that
   are not fully implemented in Wine, the native DLL might work
   much worse than the corresponding built-in one, if at all. For
   example, the native Windows GDI library must be paired with a
   Windows display driver, which of course is not present under
   Intel Unix and Wine.

   Finally, occasionally built-in Wine DLLs implement more
   features than the corresponding native Windows DLLs. Probably
   the most important example of such behavior is the integration
   of Wine with X provided by Wine's built-in USER DLL. Should the
   native Windows USER library take load-order precedence, such
   features as the ability to use the clipboard or drag-and-drop
   between Wine windows and X windows will be lost.
     __________________________________________________________

Deciding Between Native and Built-In DLLs

   Clearly, there is no one rule-of-thumb regarding which
   load-order to use. So, you must become familiar with what
   specific DLLs do and which other DLLs or features a given
   library interacts with, and use this information to make a
   case-by-case decision.
     __________________________________________________________

Load Order for DLLs

   The default load order follows this algorithm: for all DLLs
   which have a fully-functional Wine implementation, or where the
   native DLL is known not to work, the built-in library will be
   loaded first. In all other cases, the native DLL takes
   load-order precedence.

   See The Wine User Guide for informations on how to change the
   settings.
     __________________________________________________________

Memory management

   Every Win32 process in Wine has its own dedicated native
   process on the host system, and therefore its own address
   space. This section explores the layout of the Windows address
   space and how it is emulated.

   Firstly, a quick recap of how virtual memory works. Physical
   memory in RAM chips is split into frames, and the memory that
   each process sees is split into pages. Each process has its own
   4 gigabytes of address space (4gig being the maximum space
   addressable with a 32 bit pointer). Pages can be mapped or
   unmapped: attempts to access an unmapped page cause an
   EXCEPTION_ACCESS_VIOLATION which has the easily recognizable
   code of 0xC0000005. Any page can be mapped to any frame,
   therefore you can have multiple addresses which actually
   "contain" the same memory. Pages can also be mapped to things
   like files or swap space, in which case accessing that page
   will cause a disk access to read the contents into a free
   frame.
     __________________________________________________________

Initial layout (in Windows)

   When a Win32 process starts, it does not have a clear address
   space to use as it pleases. Many pages are already mapped by
   the operating system. In particular, the EXE file itself and
   any DLLs it needs are mapped into memory, and space has been
   reserved for the stack and a couple of heaps (zones used to
   allocate memory to the app from). Some of these things need to
   be at a fixed address, and others can be placed anywhere.

   The EXE file itself is usually mapped at address 0x400000 and
   up: indeed, most EXEs have their relocation records stripped
   which means they must be loaded at their base address and
   cannot be loaded at any other address.

   DLLs are internally much the same as EXE files but they have
   relocation records, which means that they can be mapped at any
   address in the address space. Remember we are not dealing with
   physical memory here, but rather virtual memory which is
   different for each process. Therefore OLEAUT32.DLL may be
   loaded at one address in one process, and a totally different
   one in another. Ensuring all the functions loaded into memory
   can find each other is the job of the Windows dynamic linker,
   which is a part of NTDLL.

   So, we have the EXE and its DLLs mapped into memory. Two other
   very important regions also exist: the stack and the process
   heap. The process heap is simply the equivalent of the libc
   malloc arena on UNIX: it's a region of memory managed by the OS
   which malloc/HeapAlloc partitions and hands out to the
   application. Windows applications can create several heaps but
   the process heap always exists.

   Windows 9x also implements another kind of heap: the shared
   heap. The shared heap is unusual in that anything allocated
   from it will be visible in every other process.
     __________________________________________________________

Comparison

   So far we've assumed the entire 4 gigs of address space is
   available for the application. In fact that's not so: only the
   lower 2 gigs are available, the upper 2 gigs are on Windows NT
   used by the operating system and hold the kernel (from
   0x80000000). Why is the kernel mapped into every address space?
   Mostly for performance: while it's possible to give the kernel
   its own address space too - this is what Ingo Molnars 4G/4G VM
   split patch does for Linux - it requires that every system call
   into the kernel switches address space. As that is a fairly
   expensive operation (requires flushing the translation
   lookaside buffers etc) and syscalls are made frequently it's
   best avoided by keeping the kernel mapped at a constant
   position in every processes address space.

   Basically, the comparison of memory mappings looks as follows:

   Table 2. Memory layout (Windows and Wine)
        Address      Windows 9x Windows NT Linux
   00000000-7fffffff User       User       User
   80000000-bfffffff Shared     User       User
   c0000000-ffffffff Kernel     Kernel     Kernel

   On Windows 9x, in fact only the upper gigabyte (0xC0000000 and
   up) is used by the kernel, the region from 2 to 3 gigs is a
   shared area used for loading system DLLs and for file mappings.
   The bottom 2 gigs on both NT and 9x are available for the
   programs memory allocation and stack.
     __________________________________________________________

Wine drivers

   Wine will not allow running native Windows drivers under Unix.
   This comes mainly because (look at the generic architecture
   schemas) Wine doesn't implement the kernel features of Windows
   (kernel here really means the kernel, not the KERNEL32 DLL),
   but rather sets up a proxy layer on top of the Unix kernel to
   provide the NTDLL and KERNEL32 features. This means that Wine
   doesn't provide the inner infrastructure to run native drivers,
   either from the Win9x family or from the NT family.

   In other words, Wine will only be able to provide access to a
   specific device, if and only if, 1/ this device is supported in
   Unix (there is Unix-driver to talk to it), 2/ Wine has
   implemented the proxy code to make the glue between the API of
   a Windows driver, and the Unix interface of the Unix driver.

   Wine, however, tries to implement in the various DLLs needing
   to access devices to do it through the standard Windows APIs
   for device drivers in user space. This is for example the case
   for the multimedia drivers, where Wine loads Wine builtin DLLs
   to talk to the OSS interface, or the ALSA interface. Those DLLs
   implement the same interface as any user space audio driver in
   Windows.
     __________________________________________________________

Kernel modules

   This section covers the kernel modules. As already stated, Wine
   implements the NT architecture, hence provides NTDLL for the
   core kernel functions, and KERNEL32, which is the
   implementation of the basis of the Win32 subsystem, on top of
   NTDLL.

   This chapter is made of two types of material (depending of
   their point of view). Some items will be tackled from a global
   point of view and then, when needed, explaining the split of
   work between NTDLL and KERNEL32; some others will be tackled
   from a DLL point of view (NTDLL or KERNEL32). The choice is
   made so that the output is more readable and understantable. At
   least, that's the intend (sigh).
     __________________________________________________________

The Wine initialization process

   Wine has a rather complex startup procedure, so unlike many
   programs the best place to begin exploring the code-base is not
   in fact at the main() function but instead at some of the more
   straightforward DLLs that exist on the periphery such as MSI,
   the widget library (in USER and COMCTL32) etc. The purpose of
   this section is to document and explain how Wine starts up from
   the moment the user runs "wine myprogram.exe" to the point at
   which myprogram gets control.
     __________________________________________________________

First Steps

   The actual wine binary that the user runs does not do very
   much, in fact it is only responsible for checking the threading
   model in use (NPTL vs LinuxThreads) and then invoking a new
   binary which performs the next stage in the startup sequence.
   See the beginning of this chapter for more information on this
   check and why it's necessary. You can find this code in
   loader/glibc.c. The result of this check is an exec of wine,
   potentially (on Linux) via the preloader.

   The Wine preloader is found in loader/preloader.c, and is
   required in order to impose a Win32 style address space layout
   upon the newly created Win32 process. The details of what this
   does is covered in the address space layout chapter. The
   preloader is a statically linked ELF binary which is passed the
   name of the actual Wine binary to run along with the arguments
   the user passed in from the command line. The preloader is an
   unusual program: it does not have a main() function. In
   standard ELF applications, the entry point is actually at a
   symbol named _start(): this is provided by the standard gcc
   infrastructure and normally jumps to __libc_start_main() which
   initializes glibc before passing control to the main function
   as defined by the programmer.

   The preloader takes control direct from the entry point for a
   few reasons. Firstly, it is required that glibc is not
   initialized twice: the result of such behaviour is undefined
   and subject to change without notice. Secondly, it's possible
   that as part of initializing glibc, the address space layout
   could be changed - for instance, any call to malloc() will
   initialize a heap arena which modifies the VM mappings.
   Finally, glibc does not return to _start() at any point, so by
   reusing it we avoid the need to recreate the ELF bootstrap
   stack (env, argv, auxiliary array etc).

   The preloader is responsible for two things: protecting
   important regions of the address space so the dynamic linker
   does not map shared libraries into them, and once that is done
   loading the real Wine binary off disk, linking it and starting
   it up. Normally all this is done automatically by glibc and the
   kernel but as we intercepted this process by using a static
   binary it's up to us to restart the process. The bulk of the
   code in the preloader is about loading wine and ld-linux.so.2
   off disk, linking them together, then starting the dynamic
   linking process.

   One of the last things the preloader does before jumping into
   the dynamic linker is scan the symbol table of the loaded Wine
   binary and set the value of a global variable directly: this is
   a more efficient way of passing information to the main Wine
   program than flattening the data structures into an environment
   variable or command line parameter then unpacking it on the
   other side, but it achieves pretty much the same thing. The
   global variable set points to the preload descriptor table,
   which contains the VMA regions protected by the preloader. This
   allows Wine to unmap them once the dynamic linker has been run,
   so leaving gaps we can initialize properly later on.
     __________________________________________________________

Starting the emulator

   The process of starting up the emulator itself is mostly one of
   chaining through various initializer functions defined in the
   core libraries and DLLs: libwine, then NTDLL, then KERNEL32.

   The wine binary has a main() function, defined in
   loader/main.c, so after the preloader has run we start here.
   This passes the information provided by the preloader into
   libwine and then calls wine_init(), defined in
   libs/wine/loader.c. This is where the emulation really starts:
   wine_init() can, with the correct preparation, be called from
   programs other than the wine loader itself.

   wine_init() does some very basic setup tasks such as
   initializing the debugging infrastructure, yet more address
   space manipulation (see the information on the 4G/4G VM split
   in the address space chapter), before loading NTDLL - the core
   of both Wine and the Windows NT series - and jumping to the
   __wine_process_init() function defined in dlls/ntdll/loader.c

   This function is responsible for initializing the primary Win32
   environment. In thread_init(), it sets up the TEB, the
   wineserver connection for the main thread and the process heap.
   See the beginning of this chapter for more information on this.

   Finally, it loads and jumps to __wine_kernel_init() in
   KERNEL32.DLL: this is defined in dlls/kernel32/process.c. This
   is where the bulk of the work is done. The KERNEL32
   initialization code retrieves the startup info for the process
   from the server, initializes the registry, sets up the drive
   mapping system and locale data, then begins loading the
   requested application itself. Each process has a STARTUPINFO
   block that can be passed into CreateProcess specifying various
   things like how the first window should be displayed: this is
   sent to the new process via the wineserver.

   After determining the type of file given to Wine by the user (a
   Win32 EXE file, a Win16 EXE, a Winelib app etc), the program is
   loaded into memory (which may involve loading and initializing
   other DLLs, the bulk of Wines startup code), before control
   reaches the end of __wine_kernel_init(). This function ends
   with the new process stack being initialized, and start_process
   being called on the new stack. Nearly there!

   The final element of initializing Wine is starting the newly
   loaded program itself. start_process() sets up the SEH backstop
   handler, calls LdrInitializeThunk() which performs the last
   part of the process initialization (such as performing
   relocations and calling the DllMain() with PROCESS_ATTACH),
   grabs the entry point of the executable and then on this line:
ExitProcess( entry( peb ) );

   ... jumps to the entry point of the program. At this point the
   users program is running and the API provided by Wine is ready
   to be used. When entry returns, the ExitProcess() API will be
   used to initialize a graceful shutdown.
     __________________________________________________________

Detailed memory management

   As already explained in previous chapter (see the Section
   called Memory management in the Chapter called Overview for the
   details), Wine creates every 32-bit Windows process in its own
   32-bit address space. Wine also tries to map at the relevant
   addresses what Windows would do. There are however a few nasty
   bits to look at.
     __________________________________________________________

Implementation

   Wine (with a bit of black magic) is able to map the main module
   at it's desired address (likely 0x400000), to create the
   process heap, its stack (as a Windows executable can ask for a
   specific stack size), Wine simply use the initial stack of the
   ELF executable for its initialisation, but creates a new stack
   (as a Win32 one) for the main thread of the executable. Wine
   also tries to map all native DLLs at their desired address, so
   that no relocation has to be performed.

   Wine also implements the shared heap so native win9x DLLs can
   be used. This heap is always created at the SYSTEM_HEAP_BASE
   address or 0x80000000 and defaults to 16 megabytes in size.

   There are a few other magic locations. The bottom 64k of memory
   is deliberately left unmapped to catch null pointer
   dereferences. The region from 64k to 1mb+64k are reserved for
   DOS compatibility and contain various DOS data structures.
   Finally, the address space also contains mappings for the Wine
   binary itself, any native libaries Wine is using, the glibc
   malloc arena and so on.
     __________________________________________________________

Laying out the address space

   Up until about the start of 2004, the Linux address space very
   much resembled the Windows 9x layout: the kernel sat in the top
   gigabyte, the bottom pages were unmapped to catch null pointer
   dereferences, and the rest was free. The kernels mmap algorithm
   was predictable: it would start by mapping files at low
   addresses and work up from there.

   The development of a series of new low level patches violated
   many of these assumptions, and resulted in Wine needing to
   force the Win32 address space layout upon the system. This
   section looks at why and how this is done.

   The exec-shield patch increases security by randomizing the
   kernels mmap algorithms. Rather than consistently choosing the
   same addresses given the same sequence of requests, the kernel
   will now choose randomized addresses. Because the Linux dynamic
   linker (ld-linux.so.2) loads DSOs into memory by using mmap,
   this means that DSOs are no longer loaded at predictable
   addresses, so making it harder to attack software by using
   buffer overflows. It also attempts to relocate certain binaries
   into a special low area of memory known as the ASCII armor so
   making it harder to jump into them when using string based
   attacks.

   Prelink is a technology that enhances startup times by
   precalculating ELF global offset tables then saving the results
   inside the native binaries themselves. By grid fitting each DSO
   into the address space, the dynamic linker does not have to
   perform as many relocations so allowing applications that
   heavily rely on dynamic linkage to be loaded into memory much
   quicker. Complex C++ applications such as Mozilla, OpenOffice
   and KDE can especially benefit from this technique.

   The 4G VM split patch was developed by Ingo Molnar. It gives
   the Linux kernel its own address space, thereby allowing
   processes to access the maximum addressable amount of memory on
   a 32-bit machine: 4 gigabytes. It allows people with lots of
   RAM to fully utilise that in any given process at the cost of
   performance: the reason behind giving the kernel a part of each
   processes address space was to avoid the overhead of switching
   on each syscall.

   Each of these changes alter the address space in a way
   incompatible with Windows. Prelink and exec-shield mean that
   the libraries Wine uses can be placed at any point in the
   address space: typically this meant that a library was sitting
   in the region that the EXE you wanted to run had to be loaded
   (remember that unlike DLLs, EXE files cannot be moved around in
   memory). The 4G VM split means that programs could receive
   pointers to the top gigabyte of address space which some are
   not prepared for (they may store extra information in the high
   bits of a pointer, for instance). In particular, in combination
   with exec-shield this one is especially deadly as it's possible
   the process heap could be allocated beyond ADDRESS_SPACE_LIMIT
   which causes Wine initialization to fail.

   The solution to these problems is for Wine to reserve
   particular parts of the address space so that areas that we
   don't want the system to use will be avoided. We later on
   (re/de)allocate those areas as needed. One problem is that some
   of these mappings are put in place automatically by the dynamic
   linker: for instance any libraries that Wine is linked to (like
   libc, libwine, libpthread etc) will be mapped into memory
   before Wine even gets control. In order to solve that, Wine
   overrides the default ELF initialization sequence at a low
   level and reserves the needed areas by using direct syscalls
   into the kernel (ie without linking against any other code to
   do it) before restarting the standard initialization and
   letting the dynamic linker continue. This is referred to as the
   preloader and is found in loader/preloader.c.

   Once the usual ELF boot sequence has been completed, some
   native libraries may well have been mapped above the 3gig
   limit: however, this doesn't matter as 3G is a Windows limit,
   not a Linux limit. We still have to prevent the system from
   allocating anything else above there (like the heap or other
   DLLs) though so Wine performs a binary search over the upper
   gig of address space in order to iteratively fill in the holes
   with MAP_NORESERVE mappings so the address space is allocated
   but the memory to actually back it is not. This code can be
   found in libs/wine/mmap.c:reserve_area.
     __________________________________________________________

Multi-processing in Wine

   Let's take a closer look at the way Wine loads and run
   processes in memory.
     __________________________________________________________

Starting a process from command line

   When starting a Wine process from command line (we'll get later
   on to the differences between NE, PE and Winelib executables),
   there are a couple of things Wine need to do first. A first
   executable is run to check the threading model of the
   underlying OS (see the Section called Multi-threading in Wine
   for the details) and will start the real Wine loader
   corresponding to the choosen threading model.

   Then Wine graps a few elements from the Unix world: the
   environment, the program arguments. Then the ntdll.dll.so is
   loaded into memory using the standard shared library dynamic
   loader. When loaded, NTDLL will mainly first create a decent
   Windows environment:

     * create a PEB (Process Environment Block) and a TEB (Thread
       Environment Block).
     * set up the connection to the Wine server - and eventually
       launching the Wine server if none runs
     * create the process heap

   Then Kernel32 is loaded (but now using the Windows dynamic
   loading capabilities) and a Wine specific entry point is called
   __wine_kernel_init. This function will actually handle all the
   logic of the process loading and execution, and will never
   return from it's call.

   __wine_kernel_init will undergo the following tasks:

     * initialization of program arguments from Unix program
       arguments
     * lookup of executable in the file system
     * If the file is not found, then an error is printed and the
       Wine loader stops.
     * We'll cover the non-PE file type later on, so assume for
       now it's a PE file. The PE module is loaded in memory using
       the same mechanisms as for a native DLLs (mainly mapping
       the file data and code sections into memory, and handling
       relocation if needed). Note that the dependencies on the
       module are not resolved at this point.
     * A new stack is created, which size is given in the PE
       header, and this stack is made the one of the running
       thread (which is still the only one in the process). The
       stack used at startup will no longer be used.
     * Which this new stack, ntdll.LdrInitializeThunk is called
       which performs the remaining initialization parts,
       including resolving all the DLL imports on the PE module,
       and doing the init of the TLS slots.
     * Control can now be passed to the EntryPoint of the PE
       module, which will let the executable run.
     __________________________________________________________

Creating a child process from a running process

   The steps used are closely link to what is done in the previous
   case.

   There are however a few points to look at a bit more closely.
   The inner implementation creates the child process using the
   fork() and exec() calls. This means that we don't need to check
   again for the threading model, we can use what the parent (or
   the grand-parent process...) started from command line has
   found.

   The Win32 process creation allows to pass a lot of information
   between the parent and the child. This includes object handles,
   windows title, console parameters, environment strings... Wine
   makes use of both the standard Unix inheritance mechanisms (for
   environment for example) and the Wine server (to pass from
   parent to child a chunk of data containing the relevant
   information).

   The previously described loading mechanism will check in the
   Wine server if such a chunk exists, and, if so, will perform
   the relevant initialization.

   Some further synchronization is also put in place: a parent
   will wait until the child has started, or has failed. The Wine
   server is also used to perform those tasks.
     __________________________________________________________

Starting a Winelib process

   Before going into the gory details, let's first go back to what
   a Winelib application is. It can be either a regular Unix
   executable, or a more specific Wine beast. This later form in
   fact creates two files for a given executable (say foo.exe).
   The first one, named foo will be a symbolic link to the Wine
   loader (wine). The second one, named foo.exe.so, is the
   equivalent of the .dll.so files we've already described for
   DLLs. As in Windows, an executable is, among other things, a
   module with its import and export information, as any DLL, it
   makes sense Wine uses the same mechanisms for loading native
   executables and DLLs.

   When starting a Winelib application from the command line (say
   with foo arg1 arg2), the Unix shell will execute foo as a Unix
   executable. Since this is in fact the Wine loader, Wine will
   fire up. However, will notice that it hasn't been started as
   wine but as foo, and hence, will try to load (using Unix shared
   library mechanism) the second file foo.exe.so. Wine will
   recognize a 32 bit module (with its descriptor) embedded in the
   shared library, and once the shared library loaded, it will
   proceed the same path as when loading a standard native PE
   executable.

   Wine needs to implement this second form of executable in order
   to maintain the order of initialization of some elements in the
   executable. One particular issue is when dealing with global
   C++ objects. In standard Unix executable, the call of the
   constructor to such objects is stored in the specific section
   of the executable (.init not to name it). All constructors in
   this section are called before the main() or WinMain function
   is called. Creating a Wine executable using the first form
   mentionned above will let those constructors being called
   before Wine gets a chance to initialize itself. So, any
   constructor using a Windows API will fail, because Wine
   infrastructure isn't in place. The use of the second form for
   Winelib executables ensures that we do the initialization using
   the following steps:

     * initialize the Wine infrastructure
     * load the executable into memory
     * handle the import sections for the executable
     * call the global object constructors (if any). They now can
       properly call the Windows APIs
     * call the executable entry point

   The attentive reader would have noted that the resolution of
   imports for the executable is done, as for a DLL, when the
   executable/DLL descriptor is registered. However, this is done
   also by adding a specific constructor in the .init section. For
   the above describe scheme to function properly, this
   constructor must be the first constructor to be called, before
   all the other constructors, generated by the executable itself.
   The Wine build chain takes care of that, and also generating
   the executable/DLL descriptor for the Winelib executable.
     __________________________________________________________

Multi-threading in Wine

   This section will assume you understand the basics of
   multithreading. If not there are plenty of good tutorials
   available on the net to get you started.

   Threading in Wine is somewhat complex due to several factors.
   The first is the advanced level of multithreading support
   provided by Windows - there are far more threading related
   constructs available in Win32 than the Linux equivalent
   (pthreads). The second is the need to be able to map Win32
   threads to native Linux threads which provides us with benefits
   like having the kernel schedule them without our intervention.
   While it's possible to implement threading entirely without
   kernel support, doing so is not desirable on most platforms
   that Wine runs on.
     __________________________________________________________

Threading support in Win32

   Win32 is an unusually thread friendly API. Not only is it
   entirely thread safe, but it provides many different facilities
   for working with threads. These range from the basics such as
   starting and stopping threads, to the extremely complex such as
   injecting threads into other processes and COM inter-thread
   marshalling.

   One of the primary challenges of writing Wine code therefore is
   ensuring that all our DLLs are thread safe, free of race
   conditions and so on. This isn't simple - don't be afraid to
   ask if you aren't sure whether a piece of code is thread safe
   or not!

   Win32 provides many different ways you can make your code
   thread safe however the most common are critical section and
   the interlocked functions. Critical sections are a type of
   mutex designed to protect a geographic area of code. If you
   don't want multiple threads running in a piece of code at once,
   you can protect them with calls to EnterCriticalSection() and
   LeaveCriticalSection(). The first call to
   EnterCriticalSection() by a thread will lock the section and
   continue without stopping. If another thread calls it then it
   will block until the original thread calls
   LeaveCriticalSection() again.

   It is therefore vitally important that if you use critical
   sections to make some code thread-safe, that you check every
   possible codepath out of the code to ensure that any held
   sections are left. Code like this:
if (res != ERROR_SUCCESS) return res;

   is extremely suspect in a function that also contains a call to
   EnterCriticalSection(). Be careful.

   If a thread blocks while waiting for another thread to leave a
   critical section, you will see an error from the
   RtlpWaitForCriticalSection() function, along with a note of
   which thread is holding the lock. This only appears after a
   certain timeout, normally a few seconds. It's possible the
   thread holding the lock is just being really slow which is why
   Wine won't terminate the app like a non-checked build of
   Windows would, but the most common cause is that for some
   reason a thread forgot to call LeaveCriticalSection(), or died
   while holding the lock (perhaps because it was in turn waiting
   for another lock). This doesn't just happen in Wine code: a
   deadlock while waiting for a critical section could be due to a
   bug in the app triggered by a slight difference in the
   emulation.

   Another popular mechanism available is the use of functions
   like InterlockedIncrement() and InterlockedExchange(). These
   make use of native CPU abilities to execute a single
   instruction while ensuring any other processors on the system
   cannot access memory, and allow you to do common operations
   like add/remove/check a variable in thread-safe code without
   holding a mutex. These are useful for reference counting
   especially in free-threaded (thread safe) COM objects.

   Finally, the usage of TLS slots are also popular. TLS stands
   for thread-local storage, and is a set of slots scoped local to
   a thread which you can store pointers in. Look on MSDN for the
   TlsAlloc() function to learn more about the Win32
   implementation of this. Essentially, the contents of a given
   slot will be different in each thread, so you can use this to
   store data that is only meaningful in the context of a single
   thread. On recent versions of Linux the __thread keyword
   provides a convenient interface to this functionality - a more
   portable API is exposed in the pthread library. However, these
   facilities are not used by Wine, rather, we implement Win32 TLS
   entirely ourselves.
     __________________________________________________________

The Win32 thread environment

   All Win32 code, whether from a native EXE/DLL or in Wine
   itself, expects certain constructs to be present in its
   environment. This section explores what those constructs are
   and how Wine sets them up. The lack of this environment is one
   thing that makes it hard to use Wine code directly from
   standard Linux applications - in order to interact with Win32
   code a thread must first be "adopted" by Wine.

   The first thing Win32 code requires is the TEB or "Thread
   Environment Block". This is an internal (undocumented) Windows
   structure associated with every thread which stores a variety
   of things such as TLS slots, a pointer to the threads message
   queue, the last error code and so on. You can see the
   definition of the TEB in include/thread.h, or at least what we
   know of it so far. Being internal and subject to change, the
   layout of the TEB has had to be reverse engineered from
   scratch.

   A pointer to the TEB is stored in the %fs register and can be
   accessed using NtCurrentTeb() from within Wine code. %fs
   actually stores a selector, and setting it therefore requires
   modifying the processes local descriptor table (LDT) - the code
   to do this is in lib/wine/ldt.c.

   The TEB is required by nearly all Win32 code run in the Wine
   environment, as any wineserver RPC will use it, which in turn
   implies that any code which could possibly block for instance
   by using a critical section) needs it. The TEB also holds the
   SEH exception handler chain as the first element, so if
   disassembling you see code like this:
   movl %esp, %fs:0

   ... then you are seeing the program set up an SEH handler
   frame. All threads must have at least one SEH entry, which
   normally points to the backstop handler which is ultimately
   responsible for popping up the all-too-familiar This program
   has performed an illegal operation and will be terminated"
   message. On Wine we just drop straight into the debugger. A
   full description of SEH is out of the scope of this section,
   however there are some good articles in MSJ if you are
   interested.

   All Win32-aware threads must have a wineserver connection. Many
   different APIs require the ability to communicate with the
   wineserver. In turn, the wineserver must be aware of Win32
   threads in order to be able to accurately report information to
   other parts of the program and do things like route
   inter-thread messages, dispatch APCs (asynchronous procedure
   calls) and so on. Therefore a part of thread initialization is
   initializing the thread server-side. The result is not only
   correct information in the server, but a set of file
   descriptors the thread can use to communicate with the server -
   the request fd, reply fd and wait fd (used for blocking).
     __________________________________________________________

Structured Exception Handling

   Structured Exception Handling (or SEH) is an implementation of
   exceptions inside the Windows core. It allows code written in
   different languages to throw exceptions across DLL boundaries,
   and Windows reports various errors like access violations by
   throwing them. This section looks at how it works, and how it's
   implemented in Wine.
     __________________________________________________________

How SEH works

   SEH is based on embedding EXCEPTION_REGISTRATION_RECORD
   structures in the stack. Together they form a linked list
   rooted at offset zero in the TEB (see the threading section if
   you don't know what this is). A registration record points to a
   handler function, and when an exception is thrown the handlers
   are executed in turn. Each handler returns a code, and they can
   elect to either continue through the handler chain or it can
   handle the exception and then restart the program. This is
   referred to as unwinding the stack. After each handler is
   called it's popped off the chain.

   Before the system begins unwinding the stack, it runs vectored
   handlers. This is an extension to SEH available in Windows XP,
   and allows registered functions to get a first chance to watch
   or deal with any exceptions thrown in the entire program, from
   any thread.

   A thrown exception is represented by an EXCEPTION_RECORD
   structure. It consists of a code, flags, an address and an
   arbitrary number of DWORD parameters. Language runtimes can use
   these parameters to associate language-specific information
   with the exception.

   Exceptions can be triggered by many things. They can be thrown
   explicitly by using the RaiseException API, or they can be
   triggered by a crash (ie, translated from a signal). They may
   be used internally by a language runtime to implement
   language-specific exceptions. They can also be thrown across
   DCOM connections.

   Visual C++ has various extensions to SEH which it uses to
   implement, eg, object destruction on stack unwind as well as
   the ability to throw arbitrary types. The code for this is in
   dlls/msvcrt/except.c
     __________________________________________________________

Translating signals to exceptions

   In Windows, compilers are expected to use the system exception
   interface, and the kernel itself uses the same interface to
   dynamically insert exceptions into a running program. By
   contrast on Linux the exception ABI is implemented at the
   compiler level (inside GCC and the linker) and the kernel tells
   a thread of exceptional events by sending signals. The language
   runtime may or may not translate these signals into native
   exceptions, but whatever happens the kernel does not care.

   You may think that if an app crashes, it's game over and it
   really shouldn't matter how Wine handles this. It's what you
   might intuitively guess, but you'd be wrong. In fact some
   Windows programs expect to be able to crash themselves and
   recover later without the user noticing, some contain buggy
   binary-only components from third parties and use SEH to
   swallow crashes, and still others execute privileged
   (kernel-level) instructions and expect it to work. In fact, at
   least one set of APIs (the IsBad*Ptr() series) can only be
   implemented by performing an operation that may crash and
   returning TRUE if it does, and FALSE if it doesn't! So, Wine
   needs to not only implement the SEH infrastructure but also
   translate Unix signals into SEH exceptions.

   The code to translate signals into exceptions is a part of
   NTDLL, and can be found in dlls/ntdll/signal_i386.c. This file
   sets up handlers for various signals during Wine startup, and
   for the ones that indicate exceptional conditions translates
   them into exceptions. Some signals are used by Wine internally
   and have nothing to do with SEH.

   Signal handlers in Wine run on their own stack. Each thread has
   its own signal stack which resides 4k after the TEB. This is
   important for a couple of reasons. Firstly, because there's no
   guarantee that the app thread which triggered the signal has
   enough stack space for the Wine signal handling code. In
   Windows, if a thread hits the limits of its stack it triggers a
   fault on the stack guard page. The language runtime can use
   this to grow the stack if it wants to. However, because a guard
   page violation is just a regular segfault to the kernel, that
   would lead to a nested signal handler and that gets messy
   really quick so we disallow that in Wine. Secondly, setting up
   the exception to throw requires modifying the stack of the
   thread which triggered it, which is quite hard to do when
   you're still running on it.

   Windows exceptions typically contain more information than the
   Unix standard APIs provide. For instance, a
   STATUS_ACCESS_VIOLATION exception (0xC0000005) structure
   contains the faulting address, whereas a standard Unix SIGSEGV
   just tells the app that it crashed. Usually this information is
   passed as an extra parameter to the signal handler, however its
   location and contents vary between kernels (BSD, Solaris, etc).
   This data is provided in a SIGCONTEXT structure, and on entry
   to the signal handler it contains the register state of the CPU
   before the signal was sent. Modifying it will cause the kernel
   to adjust the context before restarting the thread.
     __________________________________________________________

File management

   With time, Windows API comes closer to the old Unix paradigm
   "Everything is a file". Therefore, this whole section dedicated
   to file management will cover firstly the file management, but
   also some other objects like directories, and even devices,
   which are manipulated in Windows in a rather coherent way.
   We'll see later on some other objects fitting (more or less) in
   this picture (pipes or consoles to name a few).

   First of all, Wine, while implementing the file interface from
   Windows, needs to maps a file name (expressed in the Windows
   world) onto a file name in the Unix world. This encompasses
   several aspects: how to map the file names, how to map access
   rights (both on files and directories), how to map physical
   devices (hardisks, but also other devices - like serial or
   parallel interfaces - and even VxDs).
     __________________________________________________________

Various Windows formats for file names

   Let's first review a bit the various forms Windows uses when it
   comes to file names.
     __________________________________________________________

The DOS inheritance

   At the beginning was DOS, where each file has to sit on a
   drive, called from a single letter. For separating device names
   from directory or file names, a ':' was appended to this single
   letter, hence giving the (in)-famous C: drive designations.
   Another great invention was to use some fixed names for
   accessing devices: not only where these named fixed, in a way
   you couldn't change the name if you'd wish to, but also, they
   were insensible to the location where you were using them. For
   example, it's well known that COM1 designates the first serial
   port, but it's also true that c:\foo\bar\com1 also designates
   the first serial port. It's still true today: on XP, you still
   cannot name a file COM1, whatever the directory!!!

   Well later on (with Windows 95), Microsoft decided to overcome
   some little details in file names: this included being able to
   get out of the 8+3 format (8 letters for the name, 3 letters
   for the extension), and so being able to use "long names"
   (that's the "official" naming; as you can guess, the 8+3 format
   is a short name), and also to use very strange characters in a
   file name (like a space, or even a '.'). You could then name a
   file My File V0.1.txt, instead of myfile01.txt. Just to keep on
   the fun side of things, for many years the format used on the
   disk itself for storing the names has been the short name as
   the real one and to use some tricky aliasing techniques to
   store the long name. When some newer disk file systems have
   been introduced (NTFS with NT), in replacement of the old FAT
   system (which had little evolved since the first days of DOS),
   the long name became the real name while the short name took
   the alias role.

   Windows also started to support mounting network shares, and
   see them as they were a local disk (through a specific drive
   letter). The way it has been done changed along the years, so
   we won't go into all the details (especially on the DOS and
   Win9x side).
     __________________________________________________________

The NT way

   The introduction of NT allowed a deep change in the ways DOS
   had been handling devices:

     * There's no longer a forest of DOS drive letters (even if
       the assign was a way to create symbolic links in the
       forest), but a single hierarchical space.
     * This hierarchy includes several distinct elements. For
       example, \Device\Hardisk0\Partition0 refers to the first
       partition on the first physical hard disk of the system.
     * This hierarchy covers way more than just the files and
       drives related objects, but most of the objects in the
       system. We'll only cover here the file related part.
     * This hierarchy is not directly accessible for the Win32
       API, but only the NTDLL API. The Win32 API only allows to
       manipulate part of this hierarchy (the rest being hidden
       from the Win32 API). Of course, the part you see from Win32
       API looks very similar to the one that DOS provided.
     * Mounting a disk is performed by creating a symbol link in
       this hierarchy from \Global??\C: (the name seen from the
       Win32 API) to \Device\Harddiskvolume1 which determines the
       partition on a physical disk where C: is going to be seen.
     * Network shares are also accessible through a symbol link.
       However in this case, a symbol link is created from
       \Global??\UNC\host\share\ for the share share on the
       machine host) to what's called a network redirector, and
       which will take care of 1/ the connection to the remote
       share, 2/ handling with that remote share the rest of the
       path (after the name of the server, and the name of the
       share on that server).

       Note

   In NT naming convention, \Global?? can also be called \?? to
   shorten the access.

   All of these things, make the NT system pretty much more
   flexible (you can add new types of filesystems if you want),
   you provide a unique name space for all objects, and most
   operations boil down to creating relationship between different
   objects.
     __________________________________________________________

Wrap up

   Let's end this chapter about files in Windows with a review of
   the different formats used for file names:

     * c:\foo\bar is a full path.
     * \foo\bar is an absolute path; the full path is created by
       appending the default drive (ie. the drive of the current
       directory).
     * bar is a relative path; the full path is created by adding
       the current directory.
     * c:bar is a drive relative path. Note that the case where c:
       is the drive of the current directory is rather easy; it's
       implemented the same way as the case just below (relative
       path). In the rest of this chapter, drive relative path
       will only cover the case where the drive in the path isn't
       the drive of the default directory. The resolution of this
       to a full pathname defers according to the version of
       Windows, and some parameters. Let's take some time browsing
       through these issues. On Windows 9x (as well as on DOS),
       the system maintains a process wide set of default
       directories per drive. Hence, in this case, it will resolve
       c:bar to the default directory on drive c: plus file bar.
       Of course, the default per drive directory is updated each
       time a new current directory is set (only the current
       directory of the drive specified is modified). On Windows
       NT, things differ a bit. Since NT implements a namespace
       for file closer to a single tree (instead of 26 drives),
       having a current directory per drive is a bit ackward.
       Hence, Windows NT default behavior is to have only one
       current directory across all drives (in fact, a current
       directory expressed in the global tree) - this directory is
       of course related to a given process -, c:bar is resolved
       this way:
          + If c: is the drive of the default directory, the final
            path is the current directory plus bar.
          + Otherwise it's resolved into c:\bar.
          + In order to bridge the gap between the two
            implementations (Windows 9x and NT), NT adds a bit of
            complexity on the second case. If the =C: environment
            variable is defined, then it's value is used as a
            default directory for drive C:. This is handy, for
            example, when writing a DOS shell, where having a
            current drive per drive is still implemented, even on
            NT. This mechanism (through environment variables) is
            implemented on CMD.EXE, where those variables are set
            when you change directories with the cd. Since
            environment variables are inherited at process
            creation, the current directories settings are
            inherited by child processes, hence mimicing the
            behavior of the old DOS shell. There's no mechanism
            (in NTDLL or KERNEL32) to set up, when current
            directory changes, the relevant environment variables.
            This behavior is clearly band-aid, not a full featured
            extension of current directory behavior.
       Wine fully implements all those behaviors (the Windows 9x
       vs NT ones are triggered by the version flag in Wine).
     * \\host\share is UNC (Universal Naming Convention) path, ie.
       represents a file on a remote share.
     * \\.\device denotes a physical device installed in the
       system (as seen from the Win32 subsystem). A standard NT
       system will map it to the \??\device NT path. Then, as a
       standard configuration, \??\device is likely to be a link
       to in a physical device described and hooked into the
       \Device\ tree. For example, COM1 is a link to
       \Device\Serial0.
     * On some versions of Windows, paths were limited to MAX_PATH
       characters. To circumvent this, Microsoft allowed paths to
       be 32,767 characters long, under the conditions that the
       path is expressed in Unicode (no Ansi version), and that
       the path is prefixed with \\?\. This convention is
       applicable to any of the cases described above.

   To summarize, what we've discussed so, let's put everything
   into a single table...

   Table 1. DOS, Win32 and NT paths equivalences
   Type of path Win32 example NT equivalent Rule to construct
   Full path c:\foo\bar.txt \Global??\C:\foo\bar.txt Simple
   concatenation
   Absolute path \foo\bar.txt \Global??\J:\foo\bar.txt Simple
   concatenation using the drive of the default directory (here
   J:)
   Relative path gee\bar.txt
   \Global??\J:\mydir\mysubdir\gee\bar.txt Simple concatenation
   using the default directory (here J:\mydir\mysubdir)
   Drive relative path j:gee\bar.txt

     * On Windows 9x (and DOS), J:\toto\gee\bar.txt.
     * On Windows NT, J:\gee\bar.txt.
     * On Windows NT, J:\tata\titi\bar.txt.

     * On Windows 9x (and DOS), \toto is the default directory on
       drive J:.
     * On Windows NT, if =J: isn't set.
     * On Windows NT, if =J: is set to J:\tata\titi.

   UNC (Uniform Naming Convention) path \\host\share\foo\bar.txt
   \Global??\UNC\host\share\foo\bar.txt Simple concatenation.
   Device path \\.\device \Global??\device Simple concatenation
   Long paths \\?\...   With this prefix, paths can take up to
   32,767 characters, instead of MAX_PATH for all the others).
   Once the prefix stripped, to be handled like one of the
   previous ones, just providing internal buffers large enough).
     __________________________________________________________

Wine implementation

   We'll mainly cover in this section the way Wine opens a file
   (in the Unix sense) when given a Windows file name. This will
   include mapping the Windows path onto a Unix path (including
   the devices case), handling the access rights, the sharing
   attribute if any...
     __________________________________________________________

Mapping a Windows path into an absolute Windows path

   First of all, we described in previous section the way to
   convert any path in an absolute path. Wine implements all the
   previous algorithms in order to achieve this. Note also, that
   this transformation is done with information local to the
   process (default directory, environment variables...). We'll
   assume in the rest of this section that all paths have now been
   transformed into absolute from.
     __________________________________________________________

Mapping a Windows (absolute) path onto a Unix path

   When Wine is requested to map a path name (in DOS form, with a
   drive letter, e.g. c:\foo\bar\myfile.txt), Wine converts this
   into the following Unix path
   $(WINEPREFIX)/dosdevices/c:/foo/bar/myfile.txt. The Wine
   configuration process is responsible for setting
   $(WINEPREFIX)/dosdevices/c: to be a symbolic link pointing to
   the directory in Unix hierarchy the user wants to expose as the
   C: drive in the DOS forest of drives.

   This scheme allows:

     * a very simple algorithm to map a DOS path name into a Unix
       one (no need of Wine server calls)
     * a very configurable implementation: it's very easy to
       change a drive mapping
     * a rather readable configuration: no need of sophisticated
       tools to read a drive mapping, a ls -l
       $(WINEPREFIX)/dosdevices says it all.

   This scheme is also used to implement UNC path names. For
   example, Wine maps \\host\share\foo\bar\MyRemoteFile.txt into
   $(WINEPREFIX)/dosdevices/unc/host/share/foo/bar/MyRemoteFile.tx
   t. It's then up to the user to decide where
   $(WINEPREFIX)/dosdevices/unc/host/share shall point to (or be).
   For example, it can either be a symbolic link to a directory
   inside the local machine (just for emulation purpose), or a
   symbolic link to the mount point of a remote disk (done through
   Samba or NFS), or even the real mount point. Wine will not do
   any checking here, nor will help in actually mounting the
   remote drive.

   We've seen how Wine maps a drive letter or a UNC path onto the
   Unix hierarchy, we now have to look on a the filename is
   searched within this hierarchy. The main issue is about case
   sensivity. Here's a reminder of the various properties for the
   file systems in the field.

   Table 2. File systems' properties
   FS Name Length of elements Case sensitivity (on disk) Case
   sensitivity for lookup
   FAT, FAT16 or FAT32 Short name (8+3) Names are always stored in
   upper-case Case insensitive
   VFAT Short name (8+3) + alias on long name Short names are
   always stored in upper-case. Long names are stored with case
   preservation. Case insensitive
   NTFS Long name + alias on short name (8+3). Long names are
   stored with case preservation. Short names are always stored in
   upper-case. Case insentivite
   Linux FS (ext2fs, ext3fs, reiserfs...) Long name Case
   preserving Case sensitive

   Note Case sensitivity vs. preservation


   When we say that most systems in NT are case insensitive, this
   has to be understood for looking up for a file, where the
   matches are made in a case insensitive mode. This is different
   from VFAT or NTFS "case preservation" mechanism, which stores
   the file names as they are given when creating the file, while
   doing case insensitive matches.
   Since most file systems used in NT are case insensitive and
   since most Unix file systems are case sensitive, Wine undergo a
   case insensitive search when it has found the Unix path is has
   to look for. This means, for example, that for opening the
   $(WINEPREFIX)/dosdevices/c:/foo/bar/myfile.txt, Wine will
   recursively open all directories in the path, and check, in
   this order, for the existence of the directory entry in the
   form given in the file name (ie. case sensitive), and if it's
   not found, in a case insensitive form. This allows to also
   pass, in most Win32 file API also a Unix path (instead of a DOS
   or NT path), but we'll come back to this later. This also means
   that the algorithm described doesn't correctly handle the case
   of two files in the same directory, which names only differ on
   the case of the letters. This means, that if, in the same
   directory, two files (which names match in a case sensitive
   comparison), Wine will pick-up the right one if the filename
   given matches on of the name (in a case sensitive way), but
   will pickup one of the two (without defining the one it's going
   to pickup) if the filename given matches none of the two names
   in a case sensitive way (but in a case insensitive way). For
   example, if the two filenames are my_neat_file.txt and
   My_Neat_File.txt, Wine's behavior when opening MY_neat_FILE.txt
   is undefined.

   As Windows, at the early days, didn't support the notion of
   symbolic links on directories, lots of applications (and some
   old native DLLs) are not ready for this feature. Mainly, they
   imply that the directory structure is a tree, which has lots of
   consequences on navigating in the forest of directories (ie:
   there cannot be two ways for going from directory to another,
   there cannot be cycles...). In order to prevent some bad
   behavior for such applications, Wine sets up an option. By
   default, symbolic links on directories are not followed by
   Wine. There's an options to follow them (see the Wine User
   Guide), but this could be harmful.

   Wine considers that Unix file names are long filename. This
   seems a reasonable approach; this is also the approach followed
   by most of the Unix OSes while mounting Windows partitions
   (with filesystems like FAT, FAT32 or NTFS). Therefore, Wine
   tries to support short names the best it can. Basically, they
   are two options:

     * The filesystem on which the inspected directory lies in a
       real Windows FS (like FAT, or FAT32, or NTFS) and the OS
       has support to access the short filename (for example,
       Linux does this on FAT, FAT32 or VFAT). In this case, Wine
       makes full use of this information and really mimics the
       Windows behavior: the short filename used for any file is
       the same than on Windows.
     * If conditions listed above are not met (either, FS has no
       physical short name support, or OS doesn't provide the
       access access to the short name), Wine decides and computes
       on its own the short filename for a given long filename. We
       cannot ensure that the generated short name is the same
       than on Windows (because the algorithm on Windows takes
       into account the order of creation of files, which cannot
       be implemented in Wine: Wine would have to cache the short
       names of every directory it uses!). The short name is made
       up of part of the long name (first characters) and the rest
       with a hashed value. This has several advantages:
          + The algorithm is rather simple and low cost.
          + The algorithm is stateless (doesn't depend of the
            other files in the directory).
       But, it also has the drawbacks (of the advantages):
          + The algorithm isn't the same as on Windows, which
            means a program cannot use short names generated on
            Windows. This could happen when copying an existing
            installed program from Windows (for example, on a dual
            boot machine).
          + Two long file names can end up with the same short
            name (Windows handles the collision in this case,
            while Wine doesn't). We rely on our hash algorithm to
            lower at most this possibility (even if it exists).

   Wine also allows in most file API to give as a parameter a full
   Unix path name. This is handy when running a Wine (or Winelib)
   program from the command line, and one doesn't need to convert
   the path into the Windows form. However, Wine checks that the
   Unix path given can be accessed from one of the defined drives,
   insuring that only part of the Unix / hierarchy can be
   accessed.

   As a side note, as Unix doesn't widely provide a Unicode
   interface to the filenames, and that Windows implements
   filenames as Unicode strings (even on the physical layer with
   NTFS, the FATs variant are ANSI), we need to properly map
   between the two. At startup, Wine defines what's called the
   Unix Code Page, that's is the code page the Unix kernel uses as
   a reference for the strings. Then Wine uses this code page for
   all the mappings it has to do between a Unicode path (on the
   Windows side) and a Ansi path to be used in a Unix path API.
   Note, that this will work as long as a disk isn't mounted with
   a different code page than the one the kernel uses as a
   default.

   We describe below how Windows devices are mapped to Unix
   devices. Before that, let's finish the pure file round-up with
   some basic operations.
     __________________________________________________________

Access rights and file attributes

   Now that we have looked how Wine converts a Windows pathname
   into a Unix one, we need to cover the various meta-data
   attached to a file or a directory.

   In Windows, access rights are simplistic: a file can be
   read-only or read-write. Wine sets the read-only flag if the
   file doesn't have the Unix user-write flag set. As a matter of
   fact, there's no way Wine can return that a file cannot be read
   (that doesn't exist under Windows). The file will be seen, but
   trying to open it will return an error. The Unix exec-flag is
   never reported. Wine doesn't use this information to
   allow/forbid running a new process (as Unix does with the
   exec-flag). Last but not least: hidden files. This exists on
   Windows but not really on Unix! To be exact, in Windows, the
   hidden flag is a metadata associated to any file or directoy;
   in Unix, it's a convention based on the syntax of the file name
   (whether it starts with a '.' or not). Wine implements two
   behaviors (chosen by configuration). This impacts file names
   and directory names starting by a '.'. In first mode
   (ShowDotFile is FALSE), every file or directory starting by '.'
   is returned with the hidden flag turned on. This is the natural
   behavior on Unix (for ls or even file explorer). In the second
   mode (ShowDotFile is TRUE), Wine never sets the hidden flag,
   hence every file will be seen.

   Last but not least, before opening a file, Windows makes use of
   sharing attributes in order to check whether the file can be
   opened; for example, a process, being the first in the system
   to open a given file, could forbid, while it maintains the file
   opened, that another process opens it for write access, whereas
   open for read access would be granted. This is fully supported
   in Wine by moving all those checks in the Wine server for a
   global view on the system. Note also that what's moved in the
   Wine server is the check, when the file is opened, to implement
   the Windows sharing semantics. Further operation on the file
   (like reading and writing) will not require heavy support from
   the server.

   The other good reason for putting the code for actually opening
   a file in the server is that an opened files in Windows is
   managed through a handle, and handles can only be created in
   Wine server!

   Just a note about attributes on directories: while we can
   easily map the meaning of Windows' FILE_ATTRIBUTE_READONLY on a
   file, we cannot do it for a directory. Windows' semantic (when
   this flag is set) means do not delete the directory, while the
   w attribute in Unix means don't write nor delete it. Therefore,
   Wine uses an asymetric mapping here: if the directory (in Unix)
   isn't writable, then Wine reports the FILE_ATTRIBUTE_READONLY
   attribute; on the other way around, when asked to set a
   directory with FILE_ATTRIBUTE_READONLY attribute, Wine simply
   does nothing.
     __________________________________________________________

Operations on file

Reading and writing

   Reading and writing are the basic operations on files. Wine of
   course implements this, and bases the implementation on client
   side calls to Unix equivalents (like read() or write()). Note,
   that the Wine server is involved in any read or write
   operation, as Wine needs to transform the Windows-handle to the
   file into a Unix file descriptor it can pass to any Unix file
   function.
     __________________________________________________________

Getting a Unix fd

   This is major operation in any file related operation.
   Basically, each file opened (at the Windows level), is first
   opened in the Wine server, where the fd is stored. Then, Wine
   (on client side) uses recvmsg() to pass the fd from the wine
   server process to the client process. Since this operation
   could be lengthy, Wine implement some kind of cache mechanism
   to send it only once, but getting a fd from a handle on a file
   (or any other Unix object which can be manipulated through a
   file descriptor) still requires a round trip to the Wine
   server.
     __________________________________________________________

Locking

   Windows provides file locking capabilities. When a lock is set
   (and a lock can be set on any contiguous range in a file), it
   controls how other processes in the system will have access to
   the range in the file. Since locking range on a file are
   defined on a system wide manner, its implementation resides in
   wineserver. It tries to make use Unix file locking (if the
   underlying OS and the mounted disk where the file sits support
   this feature) with fcntl() and the F_SETLK command. If this
   isn't supported, then wineserver just pretends it works.
     __________________________________________________________

I/O control

   There's no need (so far) to implement support (for files and
   directories) for DeviceIoControl(), even if this is supported
   by Windows, but for very specific needs (like compression
   management, or file system related information). This isn't the
   case for devices (including disks), but we'll cover this in the
   hereafter section related to devices.
     __________________________________________________________

Buffering

   Wine doesn't do any buffering on file accesses but rely on the
   underlying Unix kernel for that (when possible). This scheme is
   needed because it's easier to implement multiple accesses on
   the same file at the kernel level, rather than at Wine levels.
   Doing lots of small reads on the same file can turn into a
   performance hog, because each read operation needs a round trip
   to the server in order to get a file descriptor (see above).
     __________________________________________________________

Overlapped I/O

   Windows introduced the notion of overlapped I/O. Basically, it
   just means that an I/O operation (think read / write to start
   with) will not wait until it's completed, but rather return to
   the caller as soon as possible, and let the caller handle the
   wait operation and determine when the data is ready (for a read
   operation) or has been sent (for a write operation). Note that
   the overlapped operation is linked to a specific thread.

   There are several interests to this: a server can handle
   several clients without requiring multi-threading techniques;
   you can handle an event driven model more easily (ie how to
   kill properly a server while waiting in the lengthy read()
   operation).

   Note that Microsoft's support for this feature evolved along
   the various versions of Windows. For example, Windows 95 or 98
   only supports overlapped I/O for serial and parallel ports,
   while NT supports also files, disks, sockets, pipes, or
   mailslots.

   Wine implements overlapped I/O operations. This is mainly done
   by queueing in the server a request that will be triggered when
   something the current state changes (like data available for a
   read operation). This readiness is signaled to the calling
   processing by queueing a specific APC, which will be called
   within the next waiting operation the thread will have. This
   specific APC will then do the hard work of the I/O operation.
   This scheme allows to put in place a wait mechanism, to attach
   a routine to be called (on the thread context) when the state
   changes, and to be done is a rather transparent manner
   (embedded any the generic wait operation). However, it isn't
   100% perfect. As the heavy operations are done in the context
   of the calling threads, if those operations are lengthy, there
   will be an impact on the calling thread, especially its
   latency. In order to provide an effective support for this
   overlapped I/O operations, we would need to rely on Unix kernel
   features (AIO is a good example).
     __________________________________________________________

Devices & volume management

   We've covered so far the ways file names are mapped into Unix
   paths. There's still need to cover it for devices. As a regular
   file, devices are manipulated in Windows with both read / write
   operations, but also control mechanisms (speed or parity of a
   serial line; volume name of a hard disk...). Since, this is
   also supported in Linux, there's also a need to open (in a Unix
   sense) a device when given a Windows device name. This section
   applies to DOS device names, which are seen in NT as nicknames
   to other devices.

   Firstly, Wine implements the Win32 to NT mapping as described
   above, hence every device path (in NT sense) is of the
   following form: /??/devicename (or /DosDevices/devicename). As
   Windows device names are case insensitive, Wine also converts
   them to lower case before any operation. Then, the first
   operation Wine tries is to check whether
   $(WINEPREFIX)/dosdevices/devicename exists. If so, it's used as
   the final Unix path for the device. The configuration process
   is in charge of creating for example, a symbolic link between
   $(WINEPREFIX)/dosdevices/PhysicalDrive0 and /dev/hda0. If such
   a link cannot be found, and the device name looks like a DOS
   disk name (like C:), Wine first tries to get the Unix device
   from the path $(WINEPREFIX)/dosdevices/c: (i.e. the device
   which is mounted on the target of the symbol link); if this
   doesn't give a Unix device, Wine tries whether
   $(WINEPREFIX)/dosdevices/c:: exists. If so, it's assumed to be
   a link to the actual Unix device. For example, for a CD Rom,
   $(WINEPREFIX)/dosdevices/e:: would be a symbolic link to
   /dev/cdrom. If this doesn't exist (we're still handling the a
   device name of the C: form), Wine tries to get the Unix device
   from the system information (/etc/mtab and /etc/fstab on
   Linux). We cannot apply this method in all the cases, because
   we have no insurance that the directory can actually be found.
   One could have, for example, a CD Rom which he/she want only to
   use as audio CD player (ie never mounted), thus not having any
   information of the device itself. If all of this doesn't work
   either, some basic operations are checked: if the devicename is
   NUL, then /dev/null is returned. If the device name is a
   default serial name (COM1 up to COM9) (resp. printer name LPT1
   up to LPT9), then Wine tries to open the Nth serial (resp.
   printer) in the system. Otherwise, some basic old DOS name
   support is done AUX is transformed into COM1 and PRN into
   LPT1), and the whole process is retried with those new names.

   To sum up:

   Table 3. Mapping of Windows device names into Unix device names
   Windows device name NT device name Mapping to Unix device name
   <any_path>AUX >\Global??\AUX Treated as an alias to COM1
   <any_path>PRN \Global??\PRN Treated as an alias to LPT1
   <any_path>COM1 \Global??\COM1 $(WINEPREFIX)/dosdevices/com1 (if
   the symbol link exists) or the Nth serial line in the system
   (on Linux, /dev/ttyS0).
   <any_path>LPT1 \Global??\LPT1 $(WINEPREFIX)/dosdevices/lpt1 (if
   the symbol link exists) or the Nth printer in the system (on
   Linux, /dev/lp0).
   <any_path>NUL \Global??\NUL /dev/null
   \\.\E: \Global??\E: $(WINEPREFIX)/dosdevices/e:: (if the
   symbolic link exists) or guessing the device from /etc/mtab or
   /etc/fstab.
   \\.\<device_name> \Global??\<device_name>
   $(WINEPREFIX)/dosdevices/<device_name> (if the symbol link
   exists).

   Now that we know which Unix device to open for a given Windows
   device, let's cover the operation on it. Those operations can
   either be read / write, io control (and even others).

   Read and write operations are supported on Real disks & CDROM
   devices, under several conditions:

     * Foremost, as the ReadFile() and WriteFile() calls are
       mapped onto the Unix read() and write() calls, the user
       (from the Unix perspective of the one running the Wine
       executable) must have read (resp. write) access to the
       device. It wouldn't be wise to let a user write directly to
       a hard disk!!!
     * Blocks' size for read and write but be of the size of a
       physical block (generally 512 for a hard disk, depends on
       the type of CD used), and offsets must also be a multiple
       of the block size.

   Wine also reads (if the first condition above about access
   rights is met) the volume information from a hard disk or a CD
   ROM to be displayed to a user.

   Wine also recognizes VxD as devices. But those VxD must be the
   Wine builtin ones (Wine will never allow to load native VxD).
   Those are configured with symbolic links in the
   $(WINEPREFIX)/dosdevices/ directory, and point to the actual
   builtin DLL. This DLL exports a single entry point, that Wine
   will use when a call to DeviceIoControl is made, with a handle
   opened to this VxD. This allows to provide some kind of
   compatibility for old Win9x apps, still talking directly to
   VxD. This is no longer supported on Windows NT, newest programs
   are less likely to make use of this feature, so we don't expect
   lots of development in this area, even though the framework is
   there and working. Note also that Wine doesn't provide support
   for native VxDs (as a game, report how many times this
   information is written in the documentation; as an advanced
   exercise, find how many more occurrences we need in order to
   stop questions whether it's possible or not).
     __________________________________________________________

NTDLL module

   NTDLL provides most of the services you'd expect from a kernel.
   In lots of cases, KERNEL32 APIs are just wrappers to NTDLL
   APIs. There are however, some difference in the APIs (the NTDLL
   ones have quite often a bit wider semantics than their KERNEL32
   counterparts). All the detailed functions we've described since
   the beginning of this chapter are in fact implemented in NTDLL,
   plus a great numbers of others we haven's written about yet.
     __________________________________________________________

KERNEL32 Module

   As already explained, KERNEL32 maps quite a few of its APIs to
   NTDLL. There are however a couple of things which are handled
   directly in KERNEL32. Let's cover a few of them...
     __________________________________________________________

Console

NT implementation

   Windows implements console solely in the Win32 subsystem. Under
   NT, the real implementation uses a dedicated subsystem
   csrss.exe Client/Server Run-time SubSystem) which is in charge,
   amont other things, of animating the consoles. Animating
   includes for example handling several processes on the same
   console (write operations must be atomic, but also a character
   keyed on the console must be read by a single process), or
   sending some information back to the processes (changing the
   size or attributes of the console, closing the console).
   Windows NT uses a dedicated (RPC based) protocol between each
   process being attached to a console and the csrss.exe
   subsystem, which is in charge of the UI of every console in the
   system.
     __________________________________________________________

Wine implementation

   Wine tries to integrate as much as possible into the Unix
   consoles, but the overall situation isn't perfect yet.
   Basically, Wine implements three kinds of consoles:

     * the first one is a direct mapping of the Unix console into
       the Windows environment. From the windows program point of
       view, it won't run in a Windows console, but it will see
       its standard input and output streams redirected to files;
       thoses files are hooked into the Unix console's output and
       input streams respectively. This is handy for running
       programs from a Unix command line (and use the result of
       the program as it was a Unix programs), but it lacks all
       the semantics of the Windows consoles.
     * the second and third ones are closer to the NT scheme,
       albeit different from what NT does. The wineserver plays
       the role of the csrss.exe subsystem (all requests are sent
       to it), and are then dispatched to a dedicated wine
       process, called (surprise!) wineconsole which manages the
       UI of the console. There is a running instance of
       wineconsole for every console in the system. Two flavors of
       this scheme are actually implemented: they vary on the
       backend for the wineconsole. The first one, dubbed user,
       creates a real GUI window (hence the USER name) and renders
       the console in this window. The second one uses the
       (n)curses library to take full control of an existing Unix
       console; of course, interaction with other Unix programs
       will not be as smooth as the first solution.

   The following table describes the main implementation
   differences between the three approaches.

   Table 4. Function consoles implementation comparison
   Function Bare streams Wineconsole & user backend Wineconsole &
   curses backend
   Console as a Win32 Object (and associated handles) No specific
   Win32 object is used in this case. The handles manipulated for
   the standard Win32 streams are in fact "bare handles" to their
   corresponding Unix streams. The mode manipulation functions
   (GetConsoleMode() / SetConsoleMode()) are not supported.
   Implemented in server, and a specific Winelib program
   (wineconsole) is in charge of the rendering and user input. The
   mode manipulation functions behave as expected. Implemented in
   server, and a specific Winelib program (wineconsole) is in
   charge of the rendering and user input. The mode manipulation
   functions behave as expected.
   Inheritance (including handling in CreateProcess() of
   CREATE_DETACHED, CREATE_NEW_CONSOLE flags). Not supported.
   Every process child of a process will inherit the Unix streams,
   so will also inherit the Win32 standard streams. Fully
   supported (each new console creation will be handled by the
   creation of a new USER32 window) Fully supported, except for
   the creation of a new console, which will be rendered on the
   same Unix terminal as the previous one, leading to
   unpredictable results.
   ReadFile() / WriteFile() operations Fully supported Fully
   supported Fully supported
   Screen-buffer manipulation (creation, deletion, resizing...)
   Not supported Fully supported Partly supported (this won't work
   too well as we don't control (so far) the size of underlying
   Unix terminal
   APIs for reading/writing screen-buffer content, cursor position
   Not supported Fully supported Fully supported
   APIs for manipulating the rendering window size Not supported
   Fully supported Partly supported (this won't work too well as
   we don't control (so far) the size of underlying Unix terminal
   Signaling (in particular, Ctrl-C handling) Nothing is done,
   which means that Ctrl-C will generate (as usual) a SIGINT which
   will terminate the program. Partly supported (Ctrl-C behaves as
   expected, however the other Win32 CUI signaling isn't properly
   implemented). Partly supported (Ctrl-C behaves as expected,
   however the other Win32 CUI signaling isn't properly
   implemented).

   The Win32 objects behind a console can be created in several
   occasions:

     * When the program is started from wineconsole, a new console
       object is created and will be used (inherited) by the
       process launched from wineconsole.
     * When a program, which isn't attached to a console, calls
       AllocConsole(), Wine then launches wineconsole, and
       attaches the current program to this console. In this mode,
       the USER32 mode is always selected as Wine cannot tell the
       current state of the Unix console.

   Please also note, that starting a child process with the
   CREATE_NEW_CONSOLE flag, will end-up calling AllocConsole() in
   the child process, hence creating a wineconsole with the USER32
   backend.

   Another interesting point to note is that Windows implements
   handles to console objects (input and screen buffers) only in
   the KERNEL32 DLL, and those are not sent nor seen from the
   NTDLL level, albeit, for example, console are waitable on
   input. How is this possible? Well, Windows NT is a bit tricky
   here. Regular handles have an interesting property: their
   integral value is always a multiple of four (they are likely to
   be offsets from the beginning of a table). Console handles, on
   the other hand, are not multiple of four, but have the two
   lower bit set (being a multiple of four means having the two
   lower bits reset). When KERNEL32 sees a handle with the two
   lower bits set, it then knows it's a console handle and takes
   appropriate decisions. For example, in the various
   kernel32!WaitFor*() functions, it transforms any console handle
   (input and output - strangely enough handles to console's
   screen buffers are waitable) into a dedicated wait event for
   the targetted console. There's an (undocumented) KERNEL32
   function GetConsoleInputWaitHandle() which returns the handle
   to this event in case you need it. Another interesting handling
   of those console's handles is in ReadFile() (resp.
   WriteFile()), which behavior, for console's handles, is
   transferred to ReadConsole() (resp. WriteConsole()). Note
   that's always the ANSI version of ReadConsole() /
   WriteConsole() which is called, hence using the default
   console's code page. There are some other spots affected, but
   you can look in dlls/kernel to find them all. All of this is
   implemented in Wine.

   Wine also implements the same layout of the registry for
   storing the preferences of the console as Windows does. Those
   settings can either be defined globally, or on a per process
   name basis. wineconsole provides the choice to the user to pick
   you which registry part (global, current running program) it
   wishes to modify the settings for.

   Table 5. Console registry settings
   Name Default value Purpose
   CursorSize 25 Percentage of cell height to which the cursor
   extents
   CursorVisible 1 Whether the cursor is visible or not
   EditionMode 0 The way the edition takes place in the console: 0
   is insertion mode, 1 is overwrite mode.
   ExitOnDie 1 Whether the console should close itself when last
   running program attached to it dies
   FaceName No default Name of the font to be used for display.
   When none is given, wineconsole tries its best to pick up a
   decent font
   FontSize 0x0C08 The high word in the font's cell height, and
   the low word is the font cell's width. The default value is 12
   pixels in height and 8 pixels in width.
   FontWeight 0 Weigth of the font. If none is given (or 0)
   wineconsole picks up a decent font size
   HistoryBufferSize 50 Number of entries in history buffer (not
   actually used)
   HistoryNoDup 0 Whether the history should store twice the same
   entry
   MenuMask 0 This mask only exists for Wine console handling. It
   allows to know which combination of extra keys are need to open
   the configuration window on right click. The mask can include
   MK_CONTROL or MK_SHIFT bits. This can be needed when programs
   actually need the right click to be passed to them instead of
   being intercepted by wineconsole.
   QuickEdit 0 If null, mouse events are sent to the application.
   If non null, mouse events are used to select text on the
   window. This setting must really be set on a application per
   application basis, because it deals with the fact the CUI
   application will use or not the mouse events.
   ScreenBufferSize 0x1950 The high word is the number of font
   cells in the height of the screen buffer, while the low word is
   the number of font cells in the width of the screen buffer.
   ScreenColors 0x000F Default color attribute for the screen
   buffer (low char is the foreground color, and high char is the
   background color)
   WindowSize 0x1950 The high word is the number of font cells in
   the height of the window, while the low word is the number of
   font cells in the width of the window. This window is the
   visible part of the screen buffer: this implies that a screen
   buffer must always be bigger than its window, and that the
   screen buffer can be scrolled so that every cell of the screen
   buffer can be seen in the window.
     __________________________________________________________

Win16 processes support

Starting a NE (Win16) process

   Wine is also able to run 16 bit processes, but this feature is
   only supported on Intel IA-32 architectures.

   When Wine is requested to run a NE (Win 16 process), it will in
   fact hand over the execution of it to a specific executable
   winevdm. VDM stands for Virtual DOS Machine. This winevdm is a
   Winelib application, but will in fact set up the correct 16 bit
   environment to run the executable. We will get back later on in
   details to what this means.

   Any new 16 bit process created by this executable (or its
   children) will run into the same winevdm instance. Among one
   instance, several functionalities will be provided to those 16
   bit processes, including the cooperative multitasking, sharing
   the same address space, managing the selectors for the 16 bit
   segments needed for code, data and stack.

   Note that several winevdm instances can run in the same Wine
   session, but the functionalities described above are only
   shared among a given instance, not among all the instances.
   winevdm is built as Winelib application, and hence has access
   to any facility a 32 bit application has.

   Each Win16 application is implemented in winevdm as a Win32
   thread. winevdm then implements its own scheduling facilities
   (in fact, the code for this feature is in the krnl386.exe DLL).
   Since the required Win16 scheduling is non pre-emptive, this
   doesn't require any underlying OS kernel support.
     __________________________________________________________

SysLevels

   SysLevels are an undocumented Windows-internal thread-safety
   system dedicated to 16 bit applications (or 32 bit applications
   that call - directly or indirectly - 16 bit code). They are
   basically critical sections which must be taken in a particular
   order. The mechanism is generic but there are always three
   syslevels:

     * level 1 is the Win16 mutex,
     * level 2 is the USER mutex,
     * level 3 is the GDI mutex.

   When entering a syslevel, the code (in dlls/kernel/syslevel.c)
   will check that a higher syslevel is not already held and
   produce an error if so. This is because it's not legal to enter
   level 2 while holding level 3 - first, you must leave level 3.

   Throughout the code you may see calls to _ConfirmSysLevel() and
   _CheckNotSysLevel(). These functions are essentially assertions
   about the syslevel states and can be used to check that the
   rules have not been accidentally violated. In particular,
   _CheckNotSysLevel() will break probably into the debugger) if
   the check fails. If this happens the solution is to get a
   backtrace and find out, by reading the source of the wine
   functions called along the way, how Wine got into the invalid
   state.
     __________________________________________________________

Memory management

   Every Win16 address is expressed in the form of
   selector:offset. The selector is an entry in the LDT, but a 16
   bit entry, limiting each offset to 64 KB. Hence, the maximum
   available memory to a Win16 process is 512 MB. Note, that the
   processor runs in protected mode, but using 16 bit selectors.

   Windows, for a 16 bit process, defines a few selectors to
   access the "real" memory (the one provided) by DOS. Basically,
   Wine also provides this area of memory.
     __________________________________________________________

DOS processes support

   The behaviour we just described also applies to DOS
   executables, which are handled the same way by winevdm. This is
   only supported on Intel IA-32 architectures.

   Wine implements also most of the DOS support in a Wine specific
   DLL (winedos). This DLL is called under certain conditions,
   like:

     * In winevdm, when trying to launch a DOS application (.EXE
       or .COM, .PIF).
     * In kernel32, when an attempt is made in the binary code to
       call some DOS or BIOS interrupts (like Int 21h for
       example).

   When winevdm runs a DOS program, this one runs in real mode (in
   fact in V86 mode from the IA-32 point of view).

   Wine also supports part of the DPMI (DOS Protected Mode
   Interface).

   Wine, when running a DOS programs, needs to map the 1 MB of
   virtual memory to the real memory (as seen by the DOS program).
   When this is not possible (like when someone else is already
   using this area), the DOS support is not possible. Not also
   that by doing so, access to linear address 0 is enabled (as
   it's also real mode address 0 which is valid). Hence, NULL
   pointer dereference faults are no longer caught.
     __________________________________________________________

Graphical modules

GDI Module

X Windows System interface

   The X libraries used to implement X clients (such as Wine) do
   not work properly if multiple threads access the same display
   concurrently. It is possible to compile the X libraries to
   perform their own synchronization (initiated by calling
   XInitThreads()). However, Wine does not use this approach.
   Instead Wine performs its own synchronization using the
   wine_tsx11_lock() / wine_tsx11_unlock() functions. This locking
   protects library access with a critical section, and also
   arranges things so that X libraries compiled without
   -D_REENTRANT (eg. with global errno variable) will work with
   Wine.

   In the past, all calls to X used to go through a wrapper called
   TSX...() (for "Thread Safe X ..."). While it is still being
   used in the code, it's inefficient as the lock is potentially
   acquired and released unnecessarily. New code should explicitly
   acquire the lock.
     __________________________________________________________

Windowing system

USER Module

   USER implements windowing and messaging subsystems. It also
   contains code for common controls and for other miscellaneous
   stuff (rectangles, clipboard, WNet, etc). Wine USER code is
   located in windows/, controls/, and misc/ directories.
     __________________________________________________________

Windowing subsystem

   windows/win.c

   windows/winpos.c

   Windows are arranged into parent/child hierarchy with one
   common ancestor for all windows (desktop window). Each window
   structure contains a pointer to the immediate ancestor (parent
   window if WS_CHILD style bit is set), a pointer to the sibling
   (returned by GetWindow(..., GW_NEXT)), a pointer to the owner
   window (set only for popup window if it was created with valid
   hwndParent parameter), and a pointer to the first child window
   (GetWindow(.., GW_CHILD)). All popup and non-child windows are
   therefore placed in the first level of this hierarchy and their
   ancestor link (wnd->parent) points to the desktop window.
   Desktop window                       - root window
    |     \      `-.
    |      \        `-.
   popup -> wnd1  ->  wnd2              - top level windows
    |       \   `-.      `-.
    |        \     `-.      `-.
   child1  child2 -> child3  child4     - child windows

   Horizontal arrows denote sibling relationship, vertical lines -
   ancestor/child. To summarize, all windows with the same
   immediate ancestor are sibling windows, all windows which do
   not have desktop as their immediate ancestor are child windows.
   Popup windows behave as topmost top-level windows unless they
   are owned. In this case the only requirement is that they must
   precede their owners in the top-level sibling list (they are
   not topmost). Child windows are confined to the client area of
   their parent windows (client area is where window gets to do
   its own drawing, non-client area consists of caption, menu,
   borders, intrinsic scrollbars, and minimize/maximize/close/help
   buttons).

   Another fairly important concept is z-order. It is derived from
   the ancestor/child hierarchy and is used to determine
   "above/below" relationship. For instance, in the example above,
   z-order is
child1->popup->child2->child3->wnd1->child4->wnd2->desktop.

   Current active window ("foreground window" in Win32) is moved
   to the front of z-order unless its top-level ancestor owns
   popup windows.

   All these issues are dealt with (or supposed to be) in
   windows/winpos.c with SetWindowPos() being the primary
   interface to the window manager.

   Wine specifics: in default and managed mode each top-level
   window gets its own X counterpart with desktop window being
   basically a fake stub. In desktop mode, however, only desktop
   window has an X window associated with it. Also, SetWindowPos()
   should eventually be implemented via Begin/End/DeferWindowPos()
   calls and not the other way around.
     __________________________________________________________

Visible region, clipping region and update region

   windows/dce.c

   windows/winpos.c

   windows/painting.c
    ________________________
   |_________               |  A and B are child windows of C
   |    A    |______        |
   |         |      |       |
   |---------'      |       |
   |   |      B     |       |
   |   |            |       |
   |   `------------'       |
   |                   C    |
   `------------------------'

   Visible region determines which part of the window is not
   obscured by other windows. If a window has the WS_CLIPCHILDREN
   style then all areas below its children are considered
   invisible. Similarly, if the WS_CLIPSIBLINGS bit is in effect
   then all areas obscured by its siblings are invisible. Child
   windows are always clipped by the boundaries of their parent
   windows.

   B has a WS_CLIPSIBLINGS style:
   .          ______
   :         |      |
   |   ,-----'      |
   |   |      B     | - visible region of B
   |   |            |
   :   `------------'

   When the program requests a display context (DC) for a window
   it can specify an optional clipping region that further
   restricts the area where the graphics output can appear. This
   area is calculated as an intersection of the visible region and
   a clipping region.

   Program asked for a DC with a clipping region:
          ______
      ,--|--.   |     .    ,--.
   ,--+--'  |   |     :   _:  |
   |  |   B |   |  => |  |    | - DC region where the painting will
   |  |     |   |     |  |    |   be visible
   `--|-----|---'     :  `----'
      `-----'

   When the window manager detects that some part of the window
   became visible it adds this area to the update region of this
   window and then generates WM_ERASEBKGND and WM_PAINT messages.
   In addition, WM_NCPAINT message is sent when the uncovered area
   intersects a nonclient part of the window. Application must
   reply to the WM_PAINT message by calling the
   BeginPaint()/EndPaint() pair of functions. BeginPaint() returns
   a DC that uses accumulated update region as a clipping region.
   This operation cleans up invalidated area and the window will
   not receive another WM_PAINT until the window manager creates a
   new update region.

   A was moved to the left:
    ________________________       ...          / C update region
   |______                  |     :      .___ /
   | A    |_________        |  => |   ...|___|..
   |      |         |       |     |   :  |   |
   |------'         |       |     |   :  '---'
   |   |      B     |       |     |   :      \
   |   |            |       |     :            \
   |   `------------'       |                    B update region
   |                   C    |
   `------------------------'

   Windows maintains a display context cache consisting of entries
   that include the DC itself, the window to which it belongs, and
   an optional clipping region (visible region is stored in the DC
   itself). When an API call changes the state of the window tree,
   window manager has to go through the DC cache to recalculate
   visible regions for entries whose windows were involved in the
   operation. DC entries (DCE) can be either private to the
   window, or private to the window class, or shared between all
   windows (Windows 3.1 limits the number of shared DCEs to 5).
     __________________________________________________________

Messaging subsystem

   windows/queue.c

   windows/message.c

   Each Windows task/thread has its own message queue - this is
   where it gets messages from. Messages can be:

    1. generated on the fly (WM_PAINT, WM_NCPAINT, WM_TIMER)
    2. created by the system (hardware messages)
    3. posted by other tasks/threads (PostMessage)
    4. sent by other tasks/threads (SendMessage)

   Message priority:

   First the system looks for sent messages, then for posted
   messages, then for hardware messages, then it checks if the
   queue has the "dirty window" bit set, and, finally, it checks
   for expired timers. See windows/message.c.

   From all these different types of messages, only posted
   messages go directly into the private message queue. System
   messages (even in Win95) are first collected in the system
   message queue and then they either sit there until
   Get/PeekMessage gets to process them or, as in Win95, if system
   queue is getting clobbered, a special thread ("raw input
   thread") assigns them to the private queues. Sent messages are
   queued separately and the sender sleeps until it gets a reply.
   Special messages are generated on the fly depending on the
   window/queue state. If the window update region is not empty,
   the system sets the QS_PAINT bit in the owning queue and
   eventually this window receives a WM_PAINT message (WM_NCPAINT
   too if the update region intersects with the non-client area).
   A timer event is raised when one of the queue timers expire.
   Depending on the timer parameters DispatchMessage either calls
   the callback function or the window procedure. If there are no
   messages pending the task/thread sleeps until messages appear.

   There are several tricky moments (open for discussion) -

     * System message order has to be honored and messages should
       be processed within correct task/thread context. Therefore
       when Get/PeekMessage encounters unassigned system message
       and this message appears not to be for the current
       task/thread it should either skip it (or get rid of it by
       moving it into the private message queue of the target
       task/thread - Win95, AFAIK) and look further or roll back
       and then yield until this message gets processed when
       system switches to the correct context (Win16). In the
       first case we lose correct message ordering, in the second
       case we have the infamous synchronous system message queue.
       Here is a post to one of the OS/2 newsgroup I found to be
       relevant:



   " Here's the problem in a nutshell, and there is no good
   solution. Every possible solution creates a different problem.
   With a windowing system, events can go to many different
   windows. Most are sent by applications or by the OS when things
   relating to that window happen (like repainting, timers, etc.)
   Mouse input events go to the window you click on (unless some
   window captures the mouse).
   So far, no problem. Whenever an event happens, you put a
   message on the target window's message queue. Every process has
   a message queue. If the process queue fills up, the messages
   back up onto the system queue.
   This is the first cause of apps hanging the GUI. If an app
   doesn't handle messages and they back up into the system queue,
   other apps can't get any more messages. The reason is that the
   next message in line can't go anywhere, and the system won't
   skip over it.
   This can be fixed by making apps have bigger private message
   queues. The SIQ fix does this. PMQSIZE does this for systems
   without the SIQ fix. Applications can also request large queues
   on their own.
   Another source of the problem, however, happens when you
   include keyboard events. When you press a key, there's no easy
   way to know what window the keystroke message should be
   delivered to.
   Most windowing systems use a concept known as "focus". The
   window with focus gets all incoming keyboard messages. Focus
   can be changed from window to window by apps or by users
   clicking on windows.
   This is the second source of the problem. Suppose window A has
   focus. You click on window B and start typing before the window
   gets focus. Where should the keystrokes go? On the one hand,
   they should go to A until the focus actually changes to B. On
   the other hand, you probably want the keystrokes to go to B,
   since you clicked there first.
   OS/2's solution is that when a focus-changing event happens
   (like clicking on a window), OS/2 holds all messages in the
   system queue until the focus change actually happens. This way,
   subsequent keystrokes go to the window you clicked on, even if
   it takes a while for that window to get focus.
   The downside is that if the window takes a real long time to
   get focus (maybe it's not handling events, or maybe the window
   losing focus isn't handling events), everything backs up in the
   system queue and the system appears hung.
   There are a few solutions to this problem.
   One is to make focus policy asynchronous. That is, focus
   changing has absolutely nothing to do with the keyboard. If you
   click on a window and start typing before the focus actually
   changes, the keystrokes go to the first window until focus
   changes, then they go to the second. This is what X-windows
   does.
   Another is what NT does. When focus changes, keyboard events
   are held in the system message queue, but other events are
   allowed through. This is "asynchronous" because the messages in
   the system queue are delivered to the application queues in a
   different order from that with which they were posted. If a bad
   app won't handle the "lose focus" message, it's of no
   consequence - the app receiving focus will get its "gain focus"
   message, and the keystrokes will go to it.
   The NT solution also takes care of the application queue
   filling up problem. Since the system delivers messages
   asynchronously, messages waiting in the system queue will just
   sit there and the rest of the messages will be delivered to
   their apps.
   The OS/2 SIQ solution is this: When a focus-changing event
   happens, in addition to blocking further messages from the
   application queues, a timer is started. When the timer goes
   off, if the focus change has not yet happened, the bad app has
   its focus taken away and all messages targeted at that window
   are skipped. When the bad app finally handles the focus change
   message, OS/2 will detect this and stop skipping its messages.
   As for the pros and cons:
   The X-windows solution is probably the easiest. The problem is
   that users generally don't like having to wait for the focus to
   change before they start typing. On many occasions, you can
   type and the characters end up in the wrong window because
   something (usually heavy system load) is preventing the focus
   change from happening in a timely manner.
   The NT solution seems pretty nice, but making the system
   message queue asynchronous can cause similar problems to the
   X-windows problem. Since messages can be delivered out of
   order, programs must not assume that two messages posted in a
   particular order will be delivered in that same order. This can
   break legacy apps, but since Win32 always had an asynchronous
   queue, it is fair to simply tell app designers "don't do that".
   It's harder to tell app designers something like that on OS/2 -
   they'll complain "you changed the rules and our apps are
   breaking."
   The OS/2 solution's problem is that nothing happens until you
   try to change window focus, and then wait for the timeout.
   Until then, the bad app is not detected and nothing is done."

       --by David Charlap
     * Intertask/interthread SendMessage. The system has to inform
       the target queue about the forthcoming message, then it has
       to carry out the context switch and wait until the result
       is available. Win16 stores necessary parameters in the
       queue structure and then calls DirectedYield() function.
       However, in Win32 there could be several messages pending
       sent by preemptively executing threads, and in this case
       SendMessage has to build some sort of message queue for
       sent messages. Another issue is what to do with messages
       sent to the sender when it is blocked inside its own
       SendMessage.
     __________________________________________________________

Accelerators

   There are three differently sized accelerator structures
   exposed to the user:

    1. Accelerators in NE resources. This is also the internal
       layout of the global handle HACCEL (16 and 32) in Windows
       95 and Wine. Exposed to the user as Win16 global handles
       HACCEL16 and HACCEL32 by the Win16/Win32 API. These are 5
       bytes long, with no padding:

BYTE   fVirt;
WORD   key;
WORD   cmd;

    2. Accelerators in PE resources. They are exposed to the user
       only by direct accessing PE resources. These have a size of
       8 bytes:

BYTE   fVirt;
BYTE   pad0;
WORD   key;
WORD   cmd;
WORD   pad1;

    3. Accelerators in the Win32 API. These are exposed to the
       user by the CopyAcceleratorTable and CreateAcceleratorTable
       functions in the Win32 API. These have a size of 6 bytes:

BYTE   fVirt;
BYTE   pad0;
WORD   key;
WORD   cmd;

   Why two types of accelerators in the Win32 API? We can only
   guess, but my best bet is that the Win32 resource compiler
   can/does not handle struct packing. Win32 ACCEL is defined
   using #pragma(2) for the compiler but without any packing for
   RC, so it will assume #pragma(4).
     __________________________________________________________

X Windows System interface
     __________________________________________________________

Keyboard mapping

   Wine now needs to know about your keyboard layout. This
   requirement comes from a need from many apps to have the
   correct scancodes available, since they read these directly,
   instead of just taking the characters returned by the X server.
   This means that Wine now needs to have a mapping from X keys to
   the scancodes these programs expect.

   On startup, Wine will try to recognize the active X layout by
   seeing if it matches any of the defined tables. If it does,
   everything is alright. If not, you need to define it.

   To do this, open the file dlls/winex11.drv/keyboard.c and take
   a look at the existing tables.

   What you really would need to do, is find out which scancode
   each key needs to generate. Find it in the main_key_scan table,
   which looks like this:
static const int main_key_scan[MAIN_LEN] =
{
/* this is my (102-key) keyboard layout, sorry if it doesn't quite match
 yours */
0x29,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,
0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x18,0x19,0x1A,0x1B,
0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x28,0x2B,
0x2C,0x2D,0x2E,0x2F,0x30,0x31,0x32,0x33,0x34,0x35,
0x56 /* the 102nd key (actually to the right of l-shift) */
};

   Next, assign each scancode the characters imprinted on the
   keycaps. This was done (sort of) for the US 101-key keyboard,
   which you can find near the top in keyboard.c. It also shows
   that if there is no 102nd key, you can skip that.

   However, for most international 102-key keyboards, we have done
   it easy for you. The scancode layout for these already pretty
   much matches the physical layout in the main_key_scan, so all
   you need to do is to go through all the keys that generate
   characters on your main keyboard (except spacebar), and stuff
   those into an appropriate table. The only exception is that the
   102nd key, which is usually to the left of the first key of the
   last line (usually Z), must be placed on a separate line after
   the last line.

   After you have written such a table, you need to add it to the
   main_key_tab[] layout index table. This will look like this:
static struct {
WORD lang, ansi_codepage, oem_codepage;
const char (*key)[MAIN_LEN][4];
} main_key_tab[]={
...
...
{MAKELANGID(LANG_NORWEGIAN,SUBLANG_DEFAULT),  1252, 865, &main_key_NO},
...

   After you have added your table, recompile Wine and test that
   it works. If it fails to detect your table, try running
WINEDEBUG=+key,+keyboard wine > key.log 2>&1

   and look in the resulting key.log file to find the error
   messages it gives for your layout.

   Note that the LANG_* and SUBLANG_* definitions are in
   include/winnls.h, which you might need to know to find out
   which numbers your language is assigned, and find it in the
   WINEDEBUG output. The numbers will be (SUBLANG * 0x400 + LANG),
   so, for example the combination LANG_NORWEGIAN (0x14) and
   SUBLANG_DEFAULT (0x1) will be (in hex) 14 + 1*400 = 414, so
   since I'm Norwegian, I could look for 0414 in the WINEDEBUG
   output to find out why my keyboard won't detect.
     __________________________________________________________

COM in Wine

Writing COM Components for Wine

   This section describes how to create your own natively compiled
   COM components.
     __________________________________________________________

Macros to define a COM interface

   The goal of the following set of definitions is to provide a
   way to use the same header file definitions to provide both a C
   interface and a C++ object oriented interface to COM
   interfaces. The type of interface is selected automatically
   depending on the language but it is always possible to get the
   C interface in C++ by defining CINTERFACE.

   It is based on the following assumptions:

     * all COM interfaces derive from IUnknown, this should not be
       a problem.
     * the header file only defines the interface, the actual
       fields are defined separately in the C file implementing
       the interface.

   The natural approach to this problem would be to make sure we
   get a C++ class and virtual methods in C++ and a structure with
   a table of pointer to functions in C. Unfortunately the layout
   of the virtual table is compiler specific, the layout of g++
   virtual tables is not the same as that of an egcs virtual table
   which is not the same as that generated by Visual C++. There
   are work arounds to make the virtual tables compatible via
   padding but unfortunately the one which is imposed to the Wine
   emulator by the Windows binaries, i.e. the Visual C++ one, is
   the most compact of all.

   So the solution I finally adopted does not use virtual tables.
   Instead I use in-line non virtual methods that dereference the
   method pointer themselves and perform the call.

   Let's take Direct3D as an example:
#define ICOM_INTERFACE IDirect3D
#define IDirect3D_METHODS \
    ICOM_METHOD1(HRESULT,Initialize,    REFIID,) \
    ICOM_METHOD2(HRESULT,EnumDevices,   LPD3DENUMDEVICESCALLBACK,, LPVOI
D,) \
    ICOM_METHOD2(HRESULT,CreateLight,   LPDIRECT3DLIGHT*,, IUnknown*,) \
    ICOM_METHOD2(HRESULT,CreateMaterial,LPDIRECT3DMATERIAL*,, IUnknown*,
) \
    ICOM_METHOD2(HRESULT,CreateViewport,LPDIRECT3DVIEWPORT*,, IUnknown*,
) \
    ICOM_METHOD2(HRESULT,FindDevice,    LPD3DFINDDEVICESEARCH,, LPD3DFIN
DDEVICERESULT,)
#define IDirect3D_IMETHODS \
    IUnknown_IMETHODS \
    IDirect3D_METHODS
ICOM_DEFINE(IDirect3D,IUnknown)
#undef ICOM_INTERFACE

#ifdef ICOM_CINTERFACE
// *** IUnknown methods *** //
#define IDirect3D_QueryInterface(p,a,b) ICOM_CALL2(QueryInterface,p,a,b)
#define IDirect3D_AddRef(p)             ICOM_CALL (AddRef,p)
#define IDirect3D_Release(p)            ICOM_CALL (Release,p)
// *** IDirect3D methods *** //
#define IDirect3D_Initialize(p,a)       ICOM_CALL1(Initialize,p,a)
#define IDirect3D_EnumDevices(p,a,b)    ICOM_CALL2(EnumDevice,p,a,b)
#define IDirect3D_CreateLight(p,a,b)    ICOM_CALL2(CreateLight,p,a,b)
#define IDirect3D_CreateMaterial(p,a,b) ICOM_CALL2(CreateMaterial,p,a,b)
#define IDirect3D_CreateViewport(p,a,b) ICOM_CALL2(CreateViewport,p,a,b)
#define IDirect3D_FindDevice(p,a,b)     ICOM_CALL2(FindDevice,p,a,b)
#endif

   Comments:

   The ICOM_INTERFACE macro is used in the ICOM_METHOD macros to
   define the type of the 'this' pointer. Defining this macro here
   saves us the trouble of having to repeat the interface name
   everywhere. Note however that because of the way macros work, a
   macro like ICOM_METHOD1 cannot use 'ICOM_INTERFACE##_VTABLE'
   because this would give 'ICOM_INTERFACE_VTABLE' and not
   'IDirect3D_VTABLE'.

   ICOM_METHODS defines the methods specific to this interface. It
   is then aggregated with the inherited methods to form
   ICOM_IMETHODS.

   ICOM_IMETHODS defines the list of methods that are inheritable
   from this interface. It must be written manually (rather than
   using a macro to generate the equivalent code) to avoid macro
   recursion (which compilers don't like).

   The ICOM_DEFINE finally declares all the structures necessary
   for the interface. We have to explicitly use the interface name
   for macro expansion reasons again. Inherited methods are
   inherited in C by using the IDirect3D_METHODS macro and the
   parent's Xxx_IMETHODS macro. In C++ we need only use the
   IDirect3D_METHODS since method inheritance is taken care of by
   the language.

   In C++ the ICOM_METHOD macros generate a function prototype and
   a call to a function pointer method. This means using once 't1
   p1, t2 p2, ...' and once 'p1, p2' without the types. The only
   way I found to handle this is to have one ICOM_METHOD macro per
   number of parameters and to have it take only the type
   information (with const if necessary) as parameters. The 'undef
   ICOM_INTERFACE' is here to remind you that using ICOM_INTERFACE
   in the following macros will not work. This time it's because
   the ICOM_CALL macro expansion is done only once the
   'IDirect3D_Xxx' macro is expanded. And by that time
   ICOM_INTERFACE will be long gone anyway.

   You may have noticed the double commas after each parameter
   type. This allows you to put the name of that parameter which I
   think is good for documentation. It is not required and since I
   did not know what to put there for this example (I could only
   find doc about IDirect3D2), I left them blank.

   Finally the set of 'IDirect3D_Xxx' macros is a standard set of
   macros defined to ease access to the interface methods in C.
   Unfortunately I don't see any way to avoid having to duplicate
   the inherited method definitions there. This time I could have
   used a trick to use only one macro whatever the number of
   parameters but I preferred to have it work the same way as
   above.

   You probably have noticed that we don't define the fields we
   need to actually implement this interface: reference count,
   pointer to other resources and miscellaneous fields. That's
   because these interfaces are just that: interfaces. They may be
   implemented more than once, in different contexts and sometimes
   not even in Wine. Thus it would not make sense to impose that
   the interface contains some specific fields.
     __________________________________________________________

Bindings in C

   In C this gives:
typedef struct IDirect3DVtbl IDirect3DVtbl;
struct IDirect3D {
    IDirect3DVtbl* lpVtbl;
};
struct IDirect3DVtbl {
    HRESULT (*fnQueryInterface)(IDirect3D* me, REFIID riid, LPVOID* ppvO
bj);
    ULONG (*fnAddRef)(IDirect3D* me);
    ULONG (*fnRelease)(IDirect3D* me);
    HRESULT (*fnInitialize)(IDirect3D* me, REFIID a);
    HRESULT (*fnEnumDevices)(IDirect3D* me, LPD3DENUMDEVICESCALLBACK a,
LPVOID b);
    HRESULT (*fnCreateLight)(IDirect3D* me, LPDIRECT3DLIGHT* a, IUnknown
* b);
    HRESULT (*fnCreateMaterial)(IDirect3D* me, LPDIRECT3DMATERIAL* a, IU
nknown* b);
    HRESULT (*fnCreateViewport)(IDirect3D* me, LPDIRECT3DVIEWPORT* a, IU
nknown* b);
    HRESULT (*fnFindDevice)(IDirect3D* me, LPD3DFINDDEVICESEARCH a, LPD3
DFINDDEVICERESULT b);
};

#ifdef ICOM_CINTERFACE
// *** IUnknown methods *** //
#define IDirect3D_QueryInterface(p,a,b) (p)->lpVtbl->fnQueryInterface(p,
a,b)
#define IDirect3D_AddRef(p)             (p)->lpVtbl->fnAddRef(p)
#define IDirect3D_Release(p)            (p)->lpVtbl->fnRelease(p)
// *** IDirect3D methods *** //
#define IDirect3D_Initialize(p,a)       (p)->lpVtbl->fnInitialize(p,a)
#define IDirect3D_EnumDevices(p,a,b)    (p)->lpVtbl->fnEnumDevice(p,a,b)
#define IDirect3D_CreateLight(p,a,b)    (p)->lpVtbl->fnCreateLight(p,a,b
)
#define IDirect3D_CreateMaterial(p,a,b) (p)->lpVtbl->fnCreateMaterial(p,
a,b)
#define IDirect3D_CreateViewport(p,a,b) (p)->lpVtbl->fnCreateViewport(p,
a,b)
#define IDirect3D_FindDevice(p,a,b)     (p)->lpVtbl->fnFindDevice(p,a,b)
#endif

   Comments:

   IDirect3D only contains a pointer to the IDirect3D virtual/jump
   table. This is the only thing the user needs to know to use the
   interface. Of course the structure we will define to implement
   this interface will have more fields but the first one will
   match this pointer.

   The code generated by ICOM_DEFINE defines both the structure
   representing the interface and the structure for the jump
   table. ICOM_DEFINE uses the parent's Xxx_IMETHODS macro to
   automatically repeat the prototypes of all the inherited
   methods and then uses IDirect3D_METHODS to define the IDirect3D
   methods.

   Each method is declared as a pointer to function field in the
   jump table. The implementation will fill this jump table with
   appropriate values, probably using a static variable, and
   initialize the lpVtbl field to point to this variable.

   The IDirect3D_Xxx macros then just dereference the lpVtbl
   pointer and use the function pointer corresponding to the macro
   name. This emulates the behavior of a virtual table and should
   be just as fast.

   This C code should be quite compatible with the Windows headers
   both for code that uses COM interfaces and for code
   implementing a COM interface.
     __________________________________________________________

Bindings in C++

   And in C++ (with gcc's g++):
typedef struct IDirect3D: public IUnknown {
    private: HRESULT (*fnInitialize)(IDirect3D* me, REFIID a);
    public: inline HRESULT Initialize(REFIID a) { return ((IDirect3D*)t.
lpVtbl)->fnInitialize(this,a); };
    private: HRESULT (*fnEnumDevices)(IDirect3D* me, LPD3DENUMDEVICESCAL
LBACK a, LPVOID b);
    public: inline HRESULT EnumDevices(LPD3DENUMDEVICESCALLBACK a, LPVOI
D b)
        { return ((IDirect3D*)t.lpVtbl)->fnEnumDevices(this,a,b); };
    private: HRESULT (*fnCreateLight)(IDirect3D* me, LPDIRECT3DLIGHT* a,
 IUnknown* b);
    public: inline HRESULT CreateLight(LPDIRECT3DLIGHT* a, IUnknown* b)
        { return ((IDirect3D*)t.lpVtbl)->fnCreateLight(this,a,b); };
    private: HRESULT (*fnCreateMaterial)(IDirect3D* me, LPDIRECT3DMATERI
AL* a, IUnknown* b);
    public: inline HRESULT CreateMaterial(LPDIRECT3DMATERIAL* a, IUnknow
n* b)
        { return ((IDirect3D*)t.lpVtbl)->fnCreateMaterial(this,a,b); };
    private: HRESULT (*fnCreateViewport)(IDirect3D* me, LPDIRECT3DVIEWPO
RT* a, IUnknown* b);
    public: inline HRESULT CreateViewport(LPDIRECT3DVIEWPORT* a, IUnknow
n* b)
        { return ((IDirect3D*)t.lpVtbl)->fnCreateViewport(this,a,b); };
    private:  HRESULT (*fnFindDevice)(IDirect3D* me, LPD3DFINDDEVICESEAR
CH a, LPD3DFINDDEVICERESULT b);
    public: inline HRESULT FindDevice(LPD3DFINDDEVICESEARCH a, LPD3DFIND
DEVICERESULT b)
        { return ((IDirect3D*)t.lpVtbl)->fnFindDevice(this,a,b); };
};

   Comments:

   In C++ IDirect3D does double duty as both the virtual/jump
   table and as the interface definition. The reason for this is
   to avoid having to duplicate the method definitions: once to
   have the function pointers in the jump table and once to have
   the methods in the interface class. Here one macro can generate
   both. This means though that the first pointer, t.lpVtbl
   defined in IUnknown, must be interpreted as the jump table
   pointer if we interpret the structure as the interface class,
   and as the function pointer to the QueryInterface method,
   t.fnQueryInterface, if we interpret the structure as the jump
   table. Fortunately this gymnastic is entirely taken care of in
   the header of IUnknown.

   Of course in C++ we use inheritance so that we don't have to
   duplicate the method definitions.

   Since IDirect3D does double duty, each ICOM_METHOD macro
   defines both a function pointer and a non-virtual inline method
   which dereferences it and calls it. This way this method
   behaves just like a virtual method but does not create a true
   C++ virtual table which would break the structure layout. If
   you look at the implementation of these methods you'll notice
   that they would not work for void functions. We have to return
   something and fortunately this seems to be what all the COM
   methods do (otherwise we would need another set of macros).

   Note how the ICOM_METHOD generates both function prototypes
   mixing types and formal parameter names and the method
   invocation using only the formal parameter name. This is the
   reason why we need different macros to handle different numbers
   of parameters.

   Finally there is no IDirect3D_Xxx macro. These are not needed
   in C++ unless the CINTERFACE macro is defined in which case we
   would not be here.

   This C++ code works well for code that just uses COM
   interfaces. But it will not work with C++ code implement a COM
   interface. That's because such code assumes the interface
   methods are declared as virtual C++ methods which is not the
   case here.
     __________________________________________________________

Implementing a COM interface.

   This continues the above example. This example assumes that the
   implementation is in C.
typedef struct _IDirect3D {
    void* lpVtbl;
    // ...
 } _IDirect3D;

static ICOM_VTABLE(IDirect3D) d3dvt;

// implement the IDirect3D methods here

int IDirect3D_fnQueryInterface(IDirect3D* me)
{
    ICOM_THIS(IDirect3D,me);
    // ...
}

// ...

static ICOM_VTABLE(IDirect3D) d3dvt = {
    ICOM_MSVTABLE_COMPAT_DummyRTTIVALUE
    IDirect3D_fnQueryInterface,
    IDirect3D_fnAdd,
    IDirect3D_fnAdd2,
    IDirect3D_fnInitialize,
    IDirect3D_fnSetWidth
};

   Comments:

   We first define what the interface really contains. This is the
   _IDirect3D structure. The first field must of course be the
   virtual table pointer. Everything else is free.

   Then we predeclare our static virtual table variable, we will
   need its address in some methods to initialize the virtual
   table pointer of the returned interface objects.

   Then we implement the interface methods. To match what has been
   declared in the header file they must take a pointer to an
   IDirect3D structure and we must cast it to an _IDirect3D so
   that we can manipulate the fields. This is performed by the
   ICOM_THIS macro.

   Finally we initialize the virtual table.
     __________________________________________________________

A brief introduction to DCOM in Wine

   This section explains the basic principles behind DCOM remoting
   as used by InstallShield and others.
     __________________________________________________________

Basics

   The basic idea behind DCOM is to take a COM object and make it
   location transparent. That means you can use it from other
   threads, processes and machines without having to worry about
   the fact that you can't just dereference the interface vtable
   pointer to call methods on it.

   You might be wondering about putting threads next to processes
   and machines in that last paragraph. You can access thread safe
   objects from multiple threads without DCOM normally, right? Why
   would you need RPC magic to do that?

   The answer is of course that COM doesn't assume that objects
   actually are thread-safe. Most real-world objects aren't, in
   fact, for various reasons. What these reasons are isn't too
   important here, though; it's just important to realize that the
   problem of thread-unsafe objects is what COM tries hard to
   solve with its apartment model. There are also ways to tell COM
   that your object is truly thread-safe (namely the free-threaded
   marshaller). In general, no object is truly thread-safe if it
   could potentially use another not so thread-safe object,
   though, so the free-threaded marshaller is less used than you'd
   think.

   For now, suffice it to say that COM lets you "marshal"
   interfaces into other "apartments". An apartment (you may see
   it referred to as a context in modern versions of COM) can be
   thought of as a location, and contains objects.

   Every thread in a program that uses COM exists in an apartment.
   If a thread wishes to use an object from another apartment,
   marshalling and the whole DCOM infrastructure gets involved to
   make that happen behind the scenes.

   So. Each COM object resides in an apartment, and each apartment
   resides in a process, and each process resides in a machine,
   and each machine resides in a network. Allowing those objects
   to be used from any of these different places is what DCOM is
   all about.

   The process of marshalling refers to taking a function call in
   an apartment and actually performing it in another apartment.
   Let's say you have two machines, A and B, and on machine B
   there is an object sitting in a DLL on the hard disk. You want
   to create an instance of that object (activate it) and use it
   as if you had compiled it into your own program. This is hard,
   because the remote object is expecting to be called by code in
   its own address space - it may do things like accept pointers
   to linked lists and even return other objects.

   Very basic marshalling is easy enough to understand. You take a
   method on a remote interface (that is a COM interface that is
   implemented on the remote computer), copy each of its
   parameters into a buffer, and send it to the remote computer.
   On the other end, the remote server reads each parameter from
   the buffer, calls the method, writes the result into another
   buffer and sends it back.

   The tricky part is exactly how to encode those parameters in
   the buffer, and how to convert standard stdcall/cdecl method
   calls to network packets and back again. This is the job of the
   RPCRT4.DLL file - or the Remote Procedure Call Runtime.

   The backbone of DCOM is this RPC runtime, which is an
   implementation of DCE RPC. DCE RPC is not naturally object
   oriented, so this protocol is extended with some new constructs
   and by assigning new meanings to some of the packet fields, to
   produce ORPC or Object RPC. You might see it called MS-RPC as
   well.

   RPC packets contain a buffer containing marshalled data in NDR
   format. NDR is short for "Network Data Representation" and is
   similar to the XDR format used in SunRPC (the closest native
   equivalent on Linux to DCE RPC). NDR/XDR are all based on the
   idea of graph serialization and were worked out during the 80s,
   meaning they are very powerful and can do things like marshal
   doubly linked lists and other rather tricky structures.

   In Wine, our DCOM implementation is not currently based on the
   RPC runtime, as while few programs use DCOM even fewer use RPC
   directly so it was developed some time after OLE32/OLEAUT32
   were. Eventually this will have to be fixed, otherwise our DCOM
   will never be compatible with Microsoft's. Bear this in mind as
   you read through the code however.
     __________________________________________________________

Proxies and Stubs

   Manually marshalling and unmarshalling each method call using
   the NDR APIs (NdrConformantArrayMarshall etc) is very tedious
   work, so the Platform SDK ships with a tool called "midl" which
   is an IDL compiler. IDL or the "Interface Definition Language"
   is a tool designed specifically for describing interfaces in a
   reasonably language neutral fashion, though in reality it bears
   a close resemblence to C++.

   By describing the functions you want to expose via RPC in IDL
   therefore, it becomes possible to pass this file to MIDL which
   spits out a huge amount of C source code. That code defines
   functions which have the same prototype as the functions
   described in your IDL but which internally take each argument,
   marshal it using Ndr, send the packet, and unmarshal the
   return.

   Because this code proxies the code from the client to the
   server, the functions are called proxies. Easy, right?

   Of course, in the RPC server process at the other end, you need
   some way to unmarshal the RPCs, so you have functions also
   generated by MIDL which are the inverse of the proxies; they
   accept an NDR buffer, extract the parameters, call the real
   function and then marshal the result back. They are called
   stubs, and stand in for the real calling code in the client
   process.

   The sort of marshalling/unmarshalling code that MIDL spits out
   can be seen in dlls/oleaut32/oaidl_p.c - it's not exactly what
   it would look like as that file contains DCOM proxies/stubs
   which are different, but you get the idea. Proxy functions take
   the arguments and feed them to the NDR marshallers (or
   picklers), invoke an NdrProxySendReceive and then convert the
   out parameters and return code. There's a ton of goop in there
   for dealing with buffer allocation, exceptions and so on - it's
   really ugly code. But, this is the basic concept behind DCE
   RPC.
     __________________________________________________________

Interface Marshalling

   Standard NDR only knows about C style function calls - they can
   accept and even return structures, but it has no concept of COM
   interfaces. Confusingly DCE RPC does have a concept of RPC
   interfaces which are just convenient ways to bundle function
   calls together into namespaces, but let's ignore that for now
   as it just muddies the water. The primary extension made by
   Microsoft to NDR then was the ability to take a COM interface
   pointer and marshal that into the NDR stream.

   The basic theory of proxies and stubs and IDL is still here,
   but it's been modified slightly. Whereas before you could
   define a bunch of functions in IDL, now a new "object" keyword
   has appeared. This tells MIDL that you're describing a COM
   interface, and as a result the proxies/stubs it generates are
   also COM objects.

   That's a very important distinction. When you make a call to a
   remote COM object you do it via a proxy object that COM has
   constructed on the fly. Likewise, a stub object on the remote
   end unpacks the RPC packet and makes the call.

   Because this is object-oriented RPC, there are a few
   complications: for instance, a call that goes via the same
   proxies/stubs may end up at a different object instance, so the
   RPC runtime keeps track of "this" and "that" in the RPC
   packets.

   This leads naturally onto the question of how we got those
   proxy/stub objects in the first place, and where they came
   from. You can use the CoCreateInstanceEx API to activate COM
   objects on a remote machine, this works like CoCreateInstance
   API. Behind the scenes, a lot of stuff is involved to do this
   (like IRemoteActivation, IOXIDResolver and so on) but let's
   gloss over that for now.

   When DCOM creates an object on a remote machine, the DCOM
   runtime on that machine activates the object in the usual way
   (by looking it up in the registry etc) and then marshals the
   requested interface back to the client. Marshalling an
   interface takes a pointer, and produces a buffer containing all
   the information DCOM needs to construct a proxy object in the
   client, a stub object in the server and link the two together.

   The structure of a marshalled interface pointer is somewhat
   complex. Let's ignore that too. The important thing is how COM
   proxies/stubs are loaded.
     __________________________________________________________

COM Proxy/Stub System

   COM proxies are objects that implement both the interfaces
   needing to be proxied and also IRpcProxyBuffer. Likewise, COM
   stubs implement IRpcStubBuffer and understand how to invoke the
   methods of the requested interface.

   You may be wondering what the word "buffer" is doing in those
   interface names. I'm not sure either, except that a running
   theme in DCOM is that interfaces which have nothing to do with
   buffers have the word Buffer appended to them, seemingly at
   random. Ignore it and don't let it confuse you :) This stuff is
   convoluted enough ...

   The IRpc[Proxy/Stub]Buffer interfaces are used to control the
   proxy/stub objects and are one of the many semi-public
   interfaces used in DCOM.

   DCOM is theoretically an internet RFC and is specced out, but
   in reality the only implementation of it apart from ours is
   Microsoft's, and as a result there are lots of interfaces which
   can be used if you want to customize or control DCOM but in
   practice are badly documented or not documented at all, or
   exist mostly as interfaces between MIDL generated code and COM
   itself. Don't pay too much attention to the MSDN definitions of
   these interfaces and APIs.

   COM proxies and stubs are like any other normal COM object -
   they are registered in the registry, they can be loaded with
   CoCreateInstance and so on. They have to be in process (in
   DLLs) however. They aren't activated directly by COM however,
   instead the process goes something like this:

     * COM receives a marshalled interface packet, and retrieves
       the IID of the marshalled interface from it
     * COM looks in
       HKEY_CLASSES_ROOT/Interface/{whatever-iid}/ProxyStubClsId32
       to retrieve the CLSID of another COM object, which
       implements IPSFactoryBuffer.
     * IPSFactoryBuffer has only two methods, CreateProxy and
       CreateStub. COM calls whichever is appropriate: CreateStub
       for the server, CreateProxy for the client. MIDL will
       normally provide an implementation of this object for you
       in the code it generates.

   Once CreateProxy has been called, the resultant object is
   QueryInterfaced to IRpcProxyBuffer, which only has 1 method,
   IRpcProxyBuffer::Connect. This method only takes one parameter,
   the IRpcChannelBuffer object which encapsulates the "RPC
   Channel" between the client and server.

   On the server side, a similar process is performed - the
   PSFactoryBuffer is created, CreateStub is called, result is QId
   to IRpcStubBuffer, and IRpcStubBuffer::Connect is used to link
   it to the RPC channel.
     __________________________________________________________

RPC Channels

   Remember the RPC runtime? Well, that's not just responsible for
   marshalling stuff, it also controls the connection and
   protocols between the client and server. We can ignore the
   details of this for now, suffice it to say that an RPC Channel
   is a COM object that implements IRpcChannelBuffer, and it's
   basically an abstraction of different RPC methods. For
   instance, in the case of inter-thread marshalling (not covered
   here) the RPC connection code isn't used, only the NDR
   marshallers are, so IRpcChannelBuffer in that case isn't
   actually implemented by RPCRT4 but rather just by the COM/OLE
   DLLS.

   On this topic, Ove Kaaven says: It depends on the Windows
   version, I think. Windows 95 and Windows NT 4 certainly had
   very different models when I looked. I'm pretty sure the
   Windows 98 version of RPCRT4 was able to dispatch messages
   directly to individual apartments. I'd be surprised if some
   similar functionality was not added to Windows 2000. After all,
   if an object on machine A wanted to use an object on machine B
   in an apartment C, wouldn't it be most efficient if the RPC
   system knew about apartments and could dispatch the message
   directly to it? And if RPC does know how to efficiently
   dispatch to apartments, why should COM duplicate this
   functionality? There were, however, no unified way to tell RPC
   about them across Windows versions, so in that old patch of
   mine, I let the COM/OLE dlls do the apartment dispatch, but
   even then, the RPC runtime was always involved. After all, it
   could be quite tricky to tell whether the call is merely
   interthread, without involving the RPC runtime...

   RPC channels are constructed on the fly by DCOM as part of the
   marshalling process. So, when you make a call on a COM proxy,
   it goes like this:

   Your code -> COM proxy object -> RPC Channel -> COM stub object
   -> Their code
     __________________________________________________________

How this actually works in Wine

   Right now, Wine does not use the NDR marshallers or RPC to
   implement its DCOM. When you marshal an interface in Wine, in
   the server process a _StubMgrThread thread is started. I
   haven't gone into the stub manager here. The important thing is
   that eventually a _StubReaderThread is started which accepts
   marshalled DCOM RPCs, and then passes them to
   IRpcStubBuffer::Invoke on the correct stub object which in turn
   demarshals the packet and performs the call. The threads
   started by our implementation of DCOM are never terminated,
   they just hang around until the process dies.

   Remember that I said our DCOM doesn't use RPC? Well, you might
   be thinking "but we use IRpcStubBuffer like we're supposed to
   ... isn't that provided by MIDL which generates code that uses
   the NDR APIs?". If so pat yourself on the back, you're still
   with me. Go get a cup of coffee.
     __________________________________________________________

Typelib Marshaller

   In fact, the reason for the PSFactoryBuffer layer of
   indirection is because not all interfaces are marshalled using
   MIDL generated code. Why not? Well, to understand that you have
   to see that one of the driving forces behind OLE and by
   extension DCOM was the development of Visual Basic. Microsoft
   wanted VB developers to be first class citizens in the COM
   world, but things like writing IDL and compiling them with a C
   compiler into DLLs wasn't easy enough.

   So, type libraries were invented. Actually they were invented
   as part of a parallel line of COM development known as "OLE
   Automation", but let's not get into that here. Type libraries
   are basically binary IDL files, except that despite there being
   two type library formats neither of them can fully express
   everything expressable in IDL. Anyway, with a type library
   (which can be embedded as a resource into a DLL) you have
   another option beyond compiling MIDL output - you can set the
   ProxyStubClsId32 registry entry for your interfaces to the
   CLSID of the "type library marshaller" or "universal
   marshaller". Both terms are used, but in the Wine source it's
   called the typelib marshaller.

   The type library marshaller constructs proxy and stub objects
   on the fly. It does so by having generic marshalling glue which
   reads the information from the type libraries, and takes the
   parameters directly off the stack. The CreateProxy method
   actually builds a vtable out of blocks of assembly stitched
   together which pass control to _xCall, which then does the
   marshalling. You can see all this magic in
   dlls/oleaut32/tmarshal.c

   In the case of InstallShield, it actually comes with typelibs
   for all the interfaces it needs to marshal (fixme: is this
   right?), but they actually use a mix of MIDL and typelib
   marshalling. In order to cover up for the fact that we don't
   really use RPC they're all forced to go via the typelib
   marshaller - that's what the 1 || hack is for and what the
   "Registering non-automation type library!" warning is about (I
   think).
     __________________________________________________________

Apartments

   Before a thread can use COM it must enter an apartment.
   Apartments are an abstraction of a COM objects thread safety
   level. There are many types of apartment but the only two we
   care about right now are single threaded apartments (STAs) and
   the multi-threaded apartment (MTA).

   Any given process may contain at most one MTA and potentially
   many STAs. This is because all objects in MTAs never care where
   they are invoked from and hence can all be treated the same.
   Since objects in STAs do care, they cannot be treated the same.

   You enter an apartment by calling CoInitializeEx() and passing
   the desired thread model in as a parameter. The default if you
   use the deprecated CoInitialize() is a STA, and this is the
   most common type of apartment used in COM.

   An object in the multi-threaded apartment may be accessed
   concurrently by multiple threads: eg, it's supposed to be
   entirely thread safe. It must also not care about
   thread-affinity, the object should react the same way no matter
   which thread is calling it.

   An object inside a STA does not have to be thread safe, and all
   calls upon it should come from the same thread - the thread
   that entered the apartment in the first place.

   The apartment system was originally designed to deal with the
   disparity between the Windows NT/C++ world in which threading
   was given a strong emphasis, and the Visual Basic world in
   which threading was barely supported and even if it had been
   fully supported most developers would not have used it. Visual
   Basic code is not truly multi-threaded, instead if you start a
   new thread you get an entirely new VM, with separate sets of
   global variables. Changes made in one thread do not reflect in
   another, which pretty much violates the expected semantics of
   multi-threading entirely but this is Visual Basic, so what did
   you expect? If you access a VB object concurrently from
   multiple threads, behind the scenes each VM runs in a STA and
   the calls are marshaled between the threads using DCOM.

   In the Windows 2000 release of COM, several new types of
   apartment were added, the most important of which are RTAs (the
   rental threaded apartment) in which concurrent access are
   serialised by COM using an apartment-wide lock but thread
   affinity is not guaranteed.
     __________________________________________________________

Structure of a marshaled interface pointer

   When an interface is marshaled using CoMarshalInterface(), the
   result is a serialized OBJREF structure. An OBJREF actually
   contains a union, but we'll be assuming the variant that embeds
   a STDOBJREF here which is what's used by the system provided
   standard marshaling. A STDOBJREF (standard object reference)
   consists of the magic signature 'MEOW', then some flags, then
   the IID of the marshaled interface. Quite what MEOW stands for
   is a mystery, but it's definitely not "Microsoft Extended
   Object Wire". Next comes the STDOBJREF flags, identified by
   their SORF_ prefix. Most of these are reserved, and their
   purpose (if any) is unknown, but a few are defined.

   After the SORF flags comes a count of the references
   represented by this marshaled interface. Typically this will be
   5 in the case of a normal marshal, but may be 0 for
   table-strong and table-weak marshals (the difference between
   these is explained below). The reasoning is this: In the
   general case, we want to know exactly when an object is
   unmarshaled and released, so we can accurately control the
   lifetime of the stub object. This is what happens when
   cPublicRefs is zero. However, in many cases, we only want to
   unmarshal an object once. Therefore, if we strengthen the rules
   to say when marshaling that we will only unmarshal once, then
   we no longer have to know when it is unmarshaled. Therefore, we
   can give out an arbitrary number of references when marshaling
   and basically say "don't call me, except when you die."

   The most interesting part of a STDOBJREF is the OXID, OID, IPID
   triple. This triple identifies any given marshaled interface
   pointer in the network. OXIDs are apartment identifiers, and
   are supposed to be unique network-wide. How this is guaranteed
   is currently unknown: the original algorithm Windows used was
   something like the current UNIX time and a local counter.

   OXIDs are generated and registered with the OXID resolver by
   performing local RPCs to the RPC subsystem (rpcss.exe). In a
   fully security-patched Windows system they appear to be
   randomly generated. This registration is done using the
   ILocalOxidResolver interface, however the exact structure of
   this interface is currently unknown.

   OIDs are object identifiers, and identify a stub manager. The
   stub manager manages interface stubs. For each exported COM
   object there are multiple interfaces and therefore multiple
   interface stubs (IRpcStubBuffer implementations). OIDs are
   apartment scoped. Each ifstub is identified by an IPID, which
   identifies a marshaled interface pointer. IPIDs are apartment
   scoped.

   Unmarshaling one of these streams therefore means setting up a
   connection to the object exporter (the apartment holding the
   marshaled interface pointer) and being able to send RPCs to the
   right ifstub. Each apartment has its own RPC endpoint and calls
   can be routed to the correct interface pointer by embedding the
   IPID into the call using RpcBindingSetObject. IRemUnknown,
   discussed below, uses a reserved IPID. Please note that this is
   true only in the current implementation. The native version
   generates an IPID as per any other object and simply notifies
   the SCM of this IPID.

   Both standard and handler marshaled OBJREFs contains an OXID
   resolver endpoint which is an RPC string binding in a
   DUALSTRINGARRAY. This is necessary because an OXID alone is not
   enough to contact the host, as it doesn't contain any network
   address data. Instead, the combination of the remote OXID
   resolver RPC endpoint and the OXID itself are passed to the
   local OXID resolver. It then returns the apartment string
   binding.

   This step is an optimisation: technically the OBJREF itself
   could contain the string binding of the apartment endpoint and
   the OXID resolver could be bypassed, but by using this DCOM can
   optimise out a server round-trip by having the local OXID
   resolver cache the query results. The OXID resolver is a
   service in the RPC subsystem (rpcss.exe) which implements a raw
   (non object-oriented) RPC interface called IOXIDResolver.
   Despite the identical naming convention this is not a COM
   interface.

   Unmarshaling an interface pointer stream therefore consists of
   reading the OXID, OID and IPID from the STDOBJREF, then reading
   one or more RPC string bindings for the remote OXID resolver.
   Then RpcBindingFromStringBinding is used to convert this remote
   string binding into an RPC binding handle which can be passed
   to the local IOXIDResolver::ResolveOxid implementation along
   with the OXID. The local OXID resolver consults its list of
   same-machine OXIDs, then its cache of remote OXIDs, and if not
   found does an RPC to the remote OXID resolver using the binding
   handle passed in earlier. The result of the query is stored for
   future reference in the cache, and finally the unmarshaling
   application gets back the apartment string binding, the IPID of
   that apartments IRemUnknown implementation, and a security hint
   (let's ignore this for now).

   Once the remote apartments string binding has been located the
   unmarshalling process constructs an RPC Channel Buffer
   implementation with the connection handle and the IPID of the
   needed interface, loads and constructs the IRpcProxyBuffer
   implementation for that IID and connects it to the channel.
   Finally the proxy is passed back to the application.
     __________________________________________________________

Handling IUnknown

   There are some subtleties here with respect to IUnknown.
   IUnknown itself is never marshaled directly: instead a version
   of it optimised for network usage is used. IRemUnknown is
   similar in concept to IUnknown except that it allows you to add
   and release arbitrary numbers of references at once, and it
   also allows you to query for multiple interfaces at once.

   IRemUnknown is used for lifecycle management, and for
   marshaling new interfaces on an object back to the client. Its
   definition can be seen in dcom.idl - basically the
   IRemUnknown::RemQueryInterface method takes an IPID and a list
   of IIDs, then returns STDOBJREFs of each new marshaled
   interface pointer.

   There is one IRemUnknown implementation per apartment, not per
   stub manager as you might expect. This is OK because IPIDs are
   apartment not object scoped (In fact, according to the DCOM
   draft spec, they are machine-scoped, but this implies
   apartment-scoped).
     __________________________________________________________

Table marshaling

   Normally once you have unmarshaled a marshaled interface
   pointer that stream is dead, you can't unmarshal it again.
   Sometimes this isn't what you want. In this case, table
   marshaling can be used. There are two types: strong and weak.
   In table-strong marshaling, selected by a specific flag to
   CoMarshalInterface(), a stream can be unmarshaled as many times
   as you like. Even if all the proxies are released, the
   marshaled object reference is still valid. Effectively the
   stream itself holds a ref on the object. To release the object
   entirely so its server can shut down, you must use
   CoReleaseMarshalData() on the stream.

   In table-weak marshaling the stream can be unmarshaled many
   times, however the stream does not hold a ref. If you unmarshal
   the stream twice, once those two proxies have been released
   remote object will also be released. Attempting to unmarshal
   the stream at this point will yield CO_E_DISCONNECTED.
     __________________________________________________________

RPC dispatch

   Exactly how RPC dispatch occurs depends on whether the exported
   object is in a STA or the MTA. If it's in the MTA then all is
   simple: the RPC dispatch thread can temporarily enter the MTA,
   perform the remote call, and then leave it again. If it's in a
   STA things get more complex, because of the requirement that
   only one thread can ever access the object.

   Instead, when entering a STA a hidden window is created
   implicitly by COM, and the user must manually pump the message
   loop in order to service incoming RPCs. The RPC dispatch thread
   performs the context switch into the STA by sending a message
   to the apartments window, which then proceeds to invoke the
   remote call in the right thread.

   RPC dispatch threads are pooled by the RPC runtime. When an
   incoming RPC needs to be serviced, a thread is pulled from the
   pool and invokes the call. The main RPC thread then goes back
   to listening for new calls. It's quite likely for objects in
   the MTA to therefore be servicing more than one call at once.
     __________________________________________________________

Message filtering and re-entrancy

   When an outgoing call is made from a STA, it's possible that
   the remote server will re-enter the client, for instance to
   perform a callback. Because of this potential re-entrancy, when
   waiting for the reply to an RPC made inside a STA, COM will
   pump the message loop. That's because while this thread is
   blocked, the incoming callback will be dispatched by a thread
   from the RPC dispatch pool, so it must be processing messages.

   While COM is pumping the message loop, all incoming messages
   from the operating system are filtered through one or more
   message filters. These filters are themselves COM objects which
   can choose to discard, hold or forward window messages. The
   default message filter drops all input messages and forwards
   the rest. This is so that if the user chooses a menu option
   which triggers an RPC, they then cannot choose that menu option
   *again* and restart the function from the beginning. That type
   of unexpected re-entrancy is extremely difficult to debug, so
   it's disallowed.

   Unfortunately other window messages are allowed through,
   meaning that it's possible your UI will be required to repaint
   itself during an outgoing RPC. This makes programming with STAs
   more complex than it may appear, as you must be prepared to run
   all kinds of code any time an outgoing call is made. In turn
   this breaks the idea that COM should abstract object location
   from the programmer, because an object that was originally
   free-threaded and is then run from a STA could trigger new and
   untested codepaths in a program.
     __________________________________________________________

Wrapup

   Theres are still a lot of topics that have not been covered:

     * Format strings/MOPs
     * IRemoteActivation
     * Complex/simple pings, distributed garbage collection
     * Marshalling IDispatch
     * ICallFrame
     * Interface pointer swizzling
     * Runtime class object registration (CoRegisterClassObject),
       ROT
     * Exactly how InstallShield uses DCOM
     __________________________________________________________

Further Reading

   Most of these documents assume you have knowledge only
   contained in other documents. You may have to reread them a few
   times for it all to make sense. Don't feel you need to read
   these to understand DCOM, you don't, you only need to look at
   them if you're planning to help implement it.

     * http://www-csag.ucsd.edu/individual/achien/cs491-f97/projec
       ts/dcom-writeup.ps
     * http://msdn.microsoft.com/library/default.asp?url=/library/
       en-us/com/htm/cmi_n2p_459u.asp
     * http://msdn.microsoft.com/library/default.asp?url=/library/
       en-us/com/htm/cmi_q2z_5ygi.asp
     * http://www.microsoft.com/msj/0398/dcom.aspx
     * http://www.microsoft.com/ntserver/techresources/appserv/COM
       /DCOM/4_ConnectionMgmt.asp
     * http://www.idevresource.com/com/library/articles/comonlinux
       .asp (unfortunately part 2 of this article does not seem to
       exist anymore, if it was ever written)
     __________________________________________________________

Wine and OpenGL

What is needed to have OpenGL support in Wine

   Basically, if you have a Linux OpenGL ABI compliant libGL (
   http://oss.sgi.com/projects/ogl-sample/ABI/) installed on your
   computer, you should have everything that is needed.

   To be more clear, I will detail one step after another what the
   configure script checks.

   If, after Wine compiles, OpenGL support is not compiled in, you
   can always check config.log to see which of the following
   points failed.
     __________________________________________________________

Header files

   The needed header files to build OpenGL support in Wine are :

   gl.h:
          the definition of all OpenGL core functions, types and
          enumerants

   glx.h:
          how OpenGL integrates in the X Window environment

   glext.h:
          the list of all registered OpenGL extensions

   The latter file (glext.h) is, as of now, not necessary to build
   Wine. But as this file can be easily obtained from SGI (
   http://oss.sgi.com/projects/ogl-sample/ABI/glext.h), and that
   all OpenGL should provide one, I decided to keep it here.
     __________________________________________________________

OpenGL library itself

   To check for the presence of 'libGL' on the system, the script
   checks if it defines the glXCreateContext function.
     __________________________________________________________

glXGetProcAddressARB function

   The core of Wine's OpenGL implementation (at least for all
   extensions) is the glXGetProcAddressARB function. Your OpenGL
   library needs to have this function defined for Wine to be able
   to support OpenGL.
     __________________________________________________________

How it all works

   The core OpenGL function calls are the same between Windows and
   Linux. So what is the difficulty to support it in Wine ? Well,
   there are two different problems :

    1. the interface to the windowing system is different for each
       OS. It's called 'GLX' for Linux (well, for X Window) and
       'wgl' for Windows. Thus, one need first to emulate one
       (wgl) with the other (GLX).
    2. the calling convention between Windows (the 'Pascal'
       convention or 'stdcall') is different from the one used on
       Linux (the 'C' convention or 'cdecl'). This means that each
       call to an OpenGL function must be 'translated' and cannot
       be used directly by the Windows program.

   Add to this some brain-dead programs (using GL calls without
   setting-up a context or deleting three time the same context)
   and you have still some work to do :-)
     __________________________________________________________

The Windowing system integration

   This integration is done at two levels :

    1. At GDI level for all pixel format selection routines (ie
       choosing if one wants a depth / alpha buffer, the size of
       these buffers, ...) and to do the 'page flipping' in double
       buffer mode. This is implemented in dlls/x11drv/opengl.c
       (all these functions are part of Wine's graphic driver
       function pointer table and thus could be reimplemented if
       ever Wine works on another Windowing system than X).
    2. In the OpenGL32.DLL itself for all other functionalities
       (context creation / deletion, querying of extension
       functions, ...). This is done in dlls/opengl32/wgl.c.
     __________________________________________________________

The thunks

   The thunks are the Wine code that does the calling convention
   translation and they are auto-generated by a Perl script. In
   Wine's Git tree, these thunks are already generated for you.
   Now, if you want to do it yourself, there is how it all
   works....

   The script is located in dlls/opengl32 and is called
   make_opengl. It requires Perl5 to work and takes an OpenGL
   version as argument. It's the version to 'simulate'. This fixes
   the list of functions that the Windows application can link
   directly to without having to query them from the OpenGL
   driver.

   This option can be 1.0 to 1.5. The default is 1.1.

   This script generates three files :

    1. opengl32.spec gives Wine's linker the signature of all
       function in the OpenGL32.DLL library so that the
       application can link them. Only 'core' functions are listed
       here.
    2. opengl_norm.c contains all the thunks for the 'core'
       functions. Your OpenGL library must provide ALL the
       function used in this file as these are not queried at run
       time.
    3. opengl_ext.c contains all the functions that are not part
       of the 'core' functions. Contrary to the thunks in
       opengl_norm.c, these functions do not depend at all on what
       your libGL provides.
       In fact, before using one of these thunks, the Windows
       program first needs to 'query' the function pointer. At
       this point, the corresponding thunk is useless. But as we
       first query the same function in libGL and store the
       returned function pointer in the thunk, the latter becomes
       functional.
     __________________________________________________________

Known problems

When running an OpenGL application, the screen flickers

   Due to restrictions (that do not exist in Windows) on OpenGL
   contexts, if you want to prevent the screen to flicker when
   using OpenGL applications (all games are using double-buffered
   contexts), you need to set the following option in your
   ~/.wine/config file in the [x11drv] section:
DesktopDoubleBuffered = Y

   and to run Wine in desktop mode.
     __________________________________________________________

Unknown extension error message:

Extension defined in the OpenGL library but NOT in opengl_ext.c...
Please report (lionel.ulmer@free.fr) !

   This means that the extension requested by the application is
   found in the libGL used by Linux (ie the call to
   glXGetProcAddressARB returns a non-NULL pointer) but that this
   string was NOT found in Wine's extension registry.

   This can come from two causes:

    1. The opengl_ext.c file is too old and needs to be generated
       again.
    2. Use of obsolete extensions that are not supported anymore
       by SGI or of 'private' extensions that are not registered.
       An example of the former are glMTexCoord2fSGIS and
       glSelectTextureSGIS as used by Quake 2 (and apparently also
       by old versions of Half Life). If documentation can be
       found on these functions, they can be added to Wine's
       extension set.

   If you have this, run with WINEDEBUG=+opengl and send me
   <lionel.ulmer@free.fr> the TRACE.
     __________________________________________________________

libopengl32.so is built but it is still not working

   This may be caused by some missing functions required by
   opengl_norm.c but that your Linux OpenGL library does not
   provide.

   To check for this, do the following steps :

    1. create a dummy .c file :

int main(void)
{
    return 0;
}

    2. try to compile it by linking both libwine and libopengl32
       (this command line supposes that you installed the Wine
       libraries in /usr/local/lib, YMMV) :

gcc dummy.c -L/usr/local/lib -lwine -lopengl32

    3. if it works, the problem is somewhere else (and you can
       send me an email). If not, you could re-generate the thunk
       files for OpenGL 1.1 for example (and send me your OpenGL
       version so that this problem can be detected at configure
       time).
     __________________________________________________________

Outline of DirectDraw Architecture

   This is an outline of the architecture. Many details are
   skipped, but hopefully this is useful.
     __________________________________________________________

DirectDraw inheritance tree

        Main
         |
        User
         |-----------\
        XVidMode    DGA2

   Most of the DirectDraw functionality is implemented in a common
   base class. Derived classes are responsible for providing
   display mode functions (Enum, Set, Restore), GetCaps, GetDevice
   identifier and internal functions called to create primary and
   backbuffer surfaces.

   User provides for DirectDraw capabilities based on drawing to a
   Wine window. It uses the User DirectDrawSurface implementation
   for primary and backbuffer surfaces.

   XVidMode attempt to use the XFree86 VidMode extension to set
   the display resolution to match the parameters to
   SetDisplayMode.

   DGA2 attempt to use the XFree86 DGA 2.x extension to set the
   display resolution and direct access to the framebuffer, if the
   full-screen-exclusive cooperative level is used. If not, it
   just uses the User implementation.
     __________________________________________________________

DirectDrawSurface inheritance tree

             Main
              |--------------\
              |              |
             DIB        Fake Z-Buffer
              |
              |------\---------\
              |      |         |
             User   DGA2   DIBTexture

   Main provides a very simple base class that does not implement
   any of the image-related functions. Therefore it does not place
   any constraints on how the surface data is stored.

   DIB stores the surface data in a DIB section. It is used by the
   Main DirectDraw driver to create off-screen surfaces.

   User implements primary and backbuffer surfaces for the User
   DirectDraw driver. If it is a primary surface, it will attempt
   to keep itself synchronized to the window.

   DGA2 surfaces claims an appropriate section of framebuffer
   space and lets DIB build its DIB section on top of it.

   Fake Z-Buffer surfaces are used by Direct3D to indicate that a
   primary surface has an associated z-buffer. For a first
   implementation, it doesn't need to store any image data since
   it is just a placeholder.

   (Actually 3D programs will rarely use Lock or GetDC on primary
   surfaces, backbuffers or z-buffers so we may want to arrange
   for lazy allocation of the DIB sections.)
     __________________________________________________________

Interface Thunks

   Only the most recent version of an interface needs to be
   implemented. Other versions are handled by having thunks
   convert their parameters and call the root version.

   Not all interface versions have thunks. Some versions could be
   combined because their parameters were compatible. For example
   if a structure changes but the structure has a dwSize field,
   methods using that structure are compatible, as long as the
   implementation remembers to take the dwSize into account.

   Interface thunks for Direct3D are more complicated since the
   paradigm changed between versions.
     __________________________________________________________

Logical Object Layout

   The objects are split into the generic part (essentially the
   fields for Main) and a private part. This is necessary because
   some objects can be created with CoCreateInstance, then
   Initialized later. Only at initialization time do we know which
   class to use. Each class except Main declares a Part structure
   and adds that to its Impl.

   For example, the DIBTexture DirectDrawSurface implementation
   looks like this:
        struct DIBTexture_DirectDrawSurfaceImpl_Part
        {
                union DIBTexture_data data; /*declared in the real heade
r*/
        };

        typedef struct
        {
                struct DIB_DirectDrawSurfaceImpl_Part dib;
                struct DIBTexture_DirectDrawSurfaceImpl_Part dibtexture;
        } DIBTexture_DirectDrawSurfaceImpl;

   So the DIBTexture surface class is derived from the DIB surface
   class and it adds one piece of data, a union.

   Main does not have a Part structure. Its fields are stored in
   IDirectDrawImpl/IDirectDrawSurfaceImpl.

   To access private data, one says
        DIBTexture_DirectDrawSurfaceImpl* priv = This->private;
        do_something_with(priv->dibtexture.data);
     __________________________________________________________

Creating Objects

   Classes have two functions relevant to object creation, Create
   and Construct. To create a new object, the class' Create
   function is called. It allocates enough memory for
   IDirectDrawImpl or IDirectDrawSurfaceImpl as well as the
   private data for derived classes and then calls Construct.

   Each class's Construct function calls the base class's
   Construct, then does the necessary initialization.

   For example, creating a primary surface with the user ddraw
   driver calls User_DirectDrawSurface_Create which allocates
   memory for the object and calls
   User_DirectDrawSurface_Construct to initialize it. This calls
   DIB_DirectDrawSurface_Construct which calls
   Main_DirectDrawSurface_Construct.
     __________________________________________________________

Wine and Multimedia

   This file contains information about the implementation of the
   multimedia layer of Wine.

   The implementation can be found in the dlls/winmm/ directory
   (and in many of its subdirectories), but also in dlls/msacm/
   (for the audio compression/decompression manager) and
   dlls/msvideo/ (for the video compression/decompression
   manager).
     __________________________________________________________

Overview

   The multimedia stuff is split into 3 layers. The low level
   (device drivers), mid level (MCI commands) and high level
   abstraction layers. The low level layer has also some helper
   DLLs (like the MSACM/MSACM32 and MSVIDEO/MSVFW32 pairs).

   All of those components are defined as DLLs (one by one).

   The low level layer may depend on current hardware and OS
   services (like OSS on Unix). It provides the core of
   playback/record using fine grain objects (audio/midi
   streams...).

   Mid level (MCI) and high level layers must be written
   independently from the hardware and OS services.

   MCI level provides some coarser grain operations (like playing
   a Midi file, or playing a video stream).
     __________________________________________________________

Multimedia architecture

Windows 95 multimedia architecture

             |
Kernel space |                    Client applications
             |
             |           | |         ^ ^       | |          | |
             |        16>| |<32   16>| |<32 16>| |<32    16>| |<32
             |           | v         | |       | v          | v
             |      +----|-----------|---------|------------|-------+
             |      |    |           |         |            |       |  W
inMM.dll
             |      |    |           |         |            |       |
32 bit
             |      +----|-----------|---------|------------|-------+
             |           | |         | ^       | |          |
             |  +------+ | |<16      | |       | |<16       |
             |  |   16>| | |         | |       | |          |
             |  |      v v v         | |       v v          v
             |  |   +---------------+---+-------------+-------------+
             |  |   | waveInXXX     |   | mciXXX      | *playSound* |
             |  |   | waveOutXXX    |   |             | mmioXXX     |
             |  |   | midiInXXX     |   |             | timeXXX     |
             |  |   | midiOutXXX    |   |             | driverXXX   |
             |  |   | midiStreamXXX |   |             |             |  M
MSystem.dll
             |  |   | mixerXXX      |   |             |             |
  16 bit
 +--------+  |  |   | auxXXX    +---+   +---+ mmThread|             |
 |MMDEVLDR|<------->| joyXXX    | Call back | mmTask  |             |
 +--------+  |  |   +-----------+-----------+---------+-------------+
     ^       |  |          |      ^    ^       | ^
     |       |  |       16>|      |<16>|    16>| |<16
     v       |  |          v      |    |       v |
 +--------+  |  |   +-------------+    +----------+
 |  VxD   |<------->|    *.drv    |    | mci*.drv |
 +--------+  |  |   +--------------+   +-----------+
             |  |    |  msacm.drv  |    | mciwave  |
             |  |    +--------------+   +-----------+
             |  |     | midimap.drv |    | mcimidi  |
             |  |     +-------------+    +-----------+
             |  |    Low-level drivers    |    ...   | MCI drivers
             |  |                         +----------+
             |  |                               |
             |  |                               |<16
             |  +-------------------------------+
             |

   The important points to notice are:

     * all drivers (and most of the core code) is 16 bit
     * all hardware (or most of it) dependent code reside in the
       kernel space (which is not surprising)
     __________________________________________________________

Windows NT multimedia architecture

   Note that Win 98 has mixed 95/NT architecture, so when speaking
   about Windows 95 (resp. NT) architecture, it refers to the type
   of architecture, not what's actually implemented. For example,
   Windows 98 implements both types of architectures.

   The important points to notice (compared to the Windows 95
   architecture) are:

     * drivers (low level, MCIs...) are 32 bit and Unicode
     * the interfaces between kernel and user drivers has changed,
       but it doesn't impact much Wine. Those changes allow some
       good things (like kernel mixing, where different apps share
       the audio hardware) and of course bad things (like kernel
       mixing, which adds latency).
     __________________________________________________________

Wine multimedia architecture

             |
Kernel space |                    Client applications
             |
             |           | |         ^ ^       | |          | |
             |        16>| |<32   16>| |<32 16>| |<32    16>| |<32
             |           | |         | |       | |          | |
             |  +------+ | |         | |       | |          | |
             |  |32/16>| | |         | |       | |          | |
             |  |      v v v         | |       v v          v v
             |  |   +---------------+---+-------------+-------------+
             |  |   | waveInXXX     |   | mciXXX      | *playSound* |
             |  |   | waveOutXXX    |   |             | mmioXXX     | Wi
nMM.dll
             |  |   | midiInXXX     |   |             | timeXXX     |
32 bit
             |  |   | midiOutXXX    |   |             | driverXXX   |
             |  |   | midiStreamXXX |   |             |             | MM
System.dll
             |  |   | mixerXXX      |   |             |             |
16 bit
             |  |   | auxXXX    +---+   +---+ mmThread|             |
             |  |   | joyXXX    | Call back | mmTask  |             |
             |  |   +-----------+-----------+---------+-------------+
             |  |         ||      ^    ^       | ^
             |  |      16>||<32   |<16>|    16>| |<16
             |  |         vv      |<32>|    32>v |<32
+---------+  |  |   +-------------+    +----------+
|HW driver|<------->|    *.drv    |    | mci*.drv |
+---------+  |  |   +--------------+   +-----------+
             |  |    |  msacm.drv  |    | mciwave  |
             |  |    +--------------+   +-----------+
             |  |     | midimap.drv |    | mcimidi  |
             |  |     +-------------+    +-----------+
             |  |    Low-level drivers    |    ...   | MCI drivers
             |  |                         +----------+
             |  |                               |
             |  |                               |<32/16
             |  +-------------------------------+
             |

   From the previous drawings, the most noticeable differences
   are:

     * low-level drivers can either be 16 or 32 bit (in fact, Wine
       supports only native wave and audio mappers).
     * MCI drivers can either be 16 or 32 bit
     * all built-in drivers (low-level and MCI) will be written as
       32 bit drivers

   Wine's WinMM automatically adapts the messages to be sent to a
   driver so that it can convert it to 16 or 32 bit interfaces.
     __________________________________________________________

Low level layers

   The low level drivers abstract the hardware specific features
   from the rest of the multimedia code. Those are implemented on
   top of mmdevapi, as new versions of windows do.

   Please note that native low level drivers are not currently
   supported in Wine, because they either access hardware
   components or require VxDs to be loaded; Wine does not
   correctly supports those two so far.

   There are two specific low level drivers (msacm.drv for wave
   input/output, midimap.drv for MIDI output only). These drivers
   (also present in Windows) allow:

     * choosing one low level driver between many (we'll discuss
       how the choice is made later on)
     * add the possibility to convert stream's format (ie ADPCM =>
       PCM) (this is useful if the format required by the
       application for playback isn't supported by the soundcard).
     * add the possibility to filter a stream (adding echo,
       equalizer... to a wave stream, or modify the instruments
       that have to be played for a MIDI stream).
     __________________________________________________________

Hardware-bound low level drivers

   Wine currently supports the following (kernel) multimedia
   interfaces.

     * Open Sound System (OSS) as supplied in the Linux and
       FreeBSD kernels by 4Front Technologies. The presence of
       this driver is checked by configure (depends on the
       <sys/soundcard.h> file). Source code resides in
       dlls/wineoss.drv.
     * Advanced Linux Sound Architecture (ALSA) as supplied in the
       Linux kernel. Source code resides in dlls/winealsa.drv.
     * Core Audio as introduced in Mac OS X 10.3. Source code
       resides in dlls/winecoreaudio.drv.
     __________________________________________________________

Wave mapper (msacm.drv)

   The Wave mapper device allows to load on-demand audio codecs in
   order to perform software conversion for the types the actual
   low level driver (hardware). Those codecs are provided through
   the standard ACM drivers in MSACM32.DLL.

   Wave mapper driver implementation can be found in
   dlls/winmm/wavemap/ directory. This driver heavily relies on
   MSACM and MSACM32 DLLs which can be found in dlls/msacm and
   dlls/msacm32. Those DLLs load ACM drivers which provide the
   conversion to PCM format (which is normally supported by low
   level drivers). A Law, uLaw, ADPCM, MP3... fit into the
   category of non PCM formats.
     __________________________________________________________

MIDI mapper (midimap.drv)

   Midi mapper allows to map each one of 16 MIDI channels to a
   specific instrument on an installed sound card. This allows for
   example to support different MIDI instrument definitions (XM,
   GM...). It also permits to output on a per channel basis to
   different MIDI renderers.

   A built-in MIDI mapper can be found in dlls/winmm/midimap/. It
   partly provides the same functionality as the Windows' one. It
   allows to pick up destination channels: you can map a given
   channel to a specific playback device channel (see the
   configuration bits for more details).
     __________________________________________________________

Mid level drivers (MCI)

   The mid level drivers are represented by some common API
   functions, mostly mciSendCommand and mciSendString. Wine
   implements several MCI mid level drivers.

   Table 1. Wine MCI drivers
   MCI Name DLL Name Role Location Comments
   CdAudio MciCDA.drv MCI interface to a CD audio player
   dlls/winmm/mcicda/ Relies on NTDLL CdRom raw interface (through
   DeviceIoControl).
   WaveAudio MciWave.drv MCI interface for wave playback and
   record dlls/winmm/mciwave/ It uses the low level audio API.
   Sequencer MciSeq.drv Midi Sequencer (playback)
   dlls/winmm/mciseq/ It uses the low level midi APIs
   AviVideo MciAvi.drv AVI playback and record dlls/winmm/mciavi/
   It rather heavily relies on MSVIDEO/MSVFW32 DLLs pair to work.
   The MCI Name column is the name of the MCI driver, as it is
   searched in configuration. The DLL Name column is the name of
   the DLL the configuration provides as a value. The name listed
   here is the default one (see the configuration section for the
   details).

   Adding a new MCI driver is just a matter of writing the
   corresponding DLL with the correct interface (see existing MCI
   drivers for the details), and to provide the relevant setup
   information for wine.inf
     __________________________________________________________

High level layers

WINMM (and MMSYSTEM)

   The high level layers encompass basically the MMSYSTEM and
   WINMM DLLs exported APIs. It also provides the skeleton for the
   core functionality for multimedia playback and recording. Note
   that native MMSYSTEM and WINMM do not currently work under Wine
   and there is no plan to support them (it would require to also
   fully support VxD, which is not done yet).

   WINMM and MMSYSTEM in Wine can handle both 16 bit and 32 bit
   drivers (for low level and MCI drivers). It will handle all the
   conversions transparently for the all the calls to WINMM and
   MMSYSTEM, as it knows what the driver interface is (16 bit or
   32 bit) and it manages the information sent accordingly.

   MCI drivers are seen as regular Wine modules, and can be loaded
   (with a correct load order between builtin, native), as any
   other DLL. Please note, that MCI drivers module names must bear
   the .drv extension to be correctly understood.

   Multimedia timers are implemented with a dedicated thread, run
   in the context of the calling process, which should correctly
   mimic Windows behavior. The only drawback is that the thread
   will appear the calling process if it enumerates the running
   processes.
     __________________________________________________________

DSOUND

   Wine also provide a DSound (DirectX) DLL with the proper COM
   implementation.

   Note that a Wine specific flag has been added to the wodOpen
   function, so that the DSound DLL can get a reference to a COM
   sound object from a given WINMM wave output device. This should
   be changed in the future.
     __________________________________________________________

MS ACM Dlls

Contents

   The MSACM32 (and its 16 bit sibbling MSACM) provide a way to
   map a given wave format to another format. It also provides
   filtering capabilities. Those DLLs only implement the proper
   switch between a caller and a driver providing the
   implementation of the requested format change or filter
   operation.

   There's nothing specific in Wine's implementation compared to
   Windows' one. Here's however a list of the builtin format
   change drivers (there's no filter driver yet):

   Table 2. Wine ACM drivers
     Name                        Provides
   imaadp32 IMA ADPCM (adaptative PCM)
   msadp32  Microsoft's ADPCM (adaptative PCM)
   msg711   Microsoft's G.711 (A-Law and u-Law)
   winemp3  Wine's MP3 (MPEG Layer 3), based on mpglib library

   Note that Wine also supports native audio codecs as well.

   All builtin ACM drivers are 32 bit Unicode DLLs
     __________________________________________________________

Caching

   The MSACM/MSACM32 keeps some data cached for all known ACM
   drivers. Under the key
          Software\Microsoft\AudioCompressionManager\DriverCache\<driver
 name>

   , are kept for values:

     * aFormatTagCache which contains an array of DWORD. There are
       two DWORDs per cFormatTags entry. The first DWORD contains
       a format tag value, and the second the associated maximum
       size for a WAVEFORMATEX structure. (Fields dwFormatTag and
       cbFormatSize from ACMFORMATDETAILS)
     * cFilterTags contains the number of tags supported by the
       driver for filtering.
     * cFormatTags contains the number of tags support by the
       driver for conversions.
     * fdwSupport (the same as the one returned from
       acmDriverDetails).

   The cFilterTags, cFormatTags, fdwSupport are the same values as
   the ones returned from acmDriverDetails function.
     __________________________________________________________

MS Video Dlls

Contents

   The MSVFW32 (and its 16 bit sibbling MSVIDEO) provide
   encode/decode video streams. Those DLLs only implement the
   proper switch between a caller and a driver providing the
   implementation of the requested format coding/decoding
   operation.

   There's nothing specific in Wine's implementation compared to
   Windows' one. Here's however a list of the builtin decoding
   drivers:

   Table 3. Wine VIDC drivers
     Name                 Provides
   msrle32  Microsoft's RLE (Run-Length encoded)
   msvidc32 Microsoft's Video-1
   iccvid   Radius Cinepak Video Decoder

   Note that Wine also supports native video codecs as well.

   All builtin VIDC drivers are 32 bit Unicode DLLs
     __________________________________________________________

Multimedia configuration

   Unfortunately, multimedia configuration evolved over time:

     * In the early days on Windows 3.x, configuration was stored
       in system.in file, under various sections ([drivers] for
       low level drivers, [mci] (resp. [mci32]) for 16 bit (resp.
       32 bit) MCI drivers...).
     * With the apparition of the registry, in Windows 95,
       configuration as been duplicated there, under the key

HKLM\System\CurrentControlSet\Control\MediaResources

     * Windows NT also adopted the registry, but decided to store
       the configuration information under another key than
       Windows 9x did.

HKLM\Software\Microsoft\Windows NT\CurrentVersion

       And with a different layout of keys and values beneath this
       key.

   Currently, Wine tries to load first a driver (low-level or MCI)
   from the NT registry settings. If it fails, it will try the
   system.ini configuration.

   An out-of-the-box configuration is provided in wine.inf, and
   shall be stored in registry and system.ini at Wine installation
   time. It will setup correctly the MCI drivers' configuration
   (as well as the wave and MIDI mappers). As the low-level
   drivers depend on hardware, their setup will be handled by
   winecfg.

   Table 4. Wine multimedia configuration scheme
   Driver Read from NT registry Read from system.ini Setup by
   wine.inf Setup by winecfg
   MCI drivers Yes (1) Yes (2) Yes No
   Wave and MIDI mappers Yes No Yes No
   Hardware-bound low level drivers Yes No No Yes
   ACM and VIDC drivers (audio & video codecs) No Yes Yes No

   This will allow most settings to be correctly loaded and
   handled. However, it won't if an app tries to search directly
   the registry for the actual configuration, as the three
   potential configuration places may not be in sync.

   It still lacks a correct installation scheme (as any multimedia
   device under Windows), so that all the correct keys are created
   in the registry. This requires an advanced model since, for
   example, the number of wave out devices can only be known on
   the destination system (depends on the sound card driven by the
   OSS interface).

   The following sections describe which type of information
   (depending on the location) Wine's multimedia DLLs understand.
     __________________________________________________________

NT configuration

   Under the
HKLM\Software\Microsoft\Windows NT\CurrentVersion

   key, are stored the names of the DLLs to be loaded for each MCI
   driver name:
            "cdaudio"="mcicda.drv"
            "sequencer"="mciseq.drv"
            "waveaudio"="mciwave.drv"
            "avivideo"="mciavi.drv"
            "videodisc"="mcipionr.drv"
            "vcr"="mcivisca.drv"
            "MPEGVideo"="mciqtz.drv"
     __________________________________________________________

system.ini

   Wine will read the MCI drivers from the [mci] or [mci32]
   section. Wine won't make any difference between the two.

   Here's a sample configuration:
   [mci]
   cdaudio=mcicda.drv
   sequencer=mciseq.drv
   waveaudio=mciwave.drv
   avivideo=mciavi.drv
   videodisc=mcipionr.drv
   vcr=mcivisca.drv
   MPEGVideo=mciqtz.drv

   ACM drivers' configuration is read (only so far) from the
   system.ini (and setup at Wine installation from the wine.inf
   file).
    [drivers32]
    MSACM.imaadpcm=imaadp32.acm
    MSACM.msadpcm=msadp32.acm
    MSACM.msg711=msg711.acm
    MSACM.winemp3=winemp3.acm

   Video (aka vidc) drivers' configuration is read (only so far)
   from the system.ini (and setup at Wine installation from the
   wine.inf file).
    [drivers32]
    VIDC.MRLE=msrle32.dll
    VIDC.MSVC=msvidc32.dll
    VIDC.CVID=iccvid.dll

   See also the configuration part of the User's Guide for other
   information on low level drivers.
     __________________________________________________________

Per driver/DLL configuration

Midi mapper

   The Midi mapper configuration is the same as on Windows 9x.
   Under the key:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Multimedia\M
IDIMap

   if the UseScheme value is not set, or is set to a null value,
   the MIDI mapper will always use the driver identified by the
   CurrentInstrument value. Note: Wine (for simplicity while
   installing) allows to define CurrentInstrument as #n (where n
   is a number), whereas Windows only allows the real device name
   here. If UseScheme is set to a non null value, CurrentScheme
   defines the name of the scheme to map the different channels.
   All the schemes are available with keys like
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\MediaProperties\Priv
ateProperties\Midi\Schemes\%name_of_scheme%

   For every scheme, under this key, will be a sub-key (which name
   is usually a two digit index, starting at 00). Its default
   value is the name of the output driver, and the value Channels
   lists all channels (of the 16 standard MIDI ones) which have to
   be copied to this driver.

   To provide enhanced configuration and mapping capabilities,
   each driver can define under the key
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\MediaProperties\Priv
ateProperties\Midi\Ports\%driver_name%

   a link to and .IDF file which allows to remap channels
   internally (for example 9 -> 16), to change instruments
   identification, event controllers values. See the source file
   dlls/winmm/midimap/midimap.c for the details (this isn't
   implemented yet).
