1. Make buffer for message large enough to hold very long file names.

[wine/multimedia.git] / DEVELOPERS-HINTS

This document should help new developers get started. Like all of Wine, it
is a work in progress.


SOURCE TREE STRUCTURE
=====================

The Wine source tree is loosely based on the original Windows modules. 
Most of the source is concerned with implementing the Wine API, although
there are also various tools, documentation, sample Winelib code, and
code specific to the binary loader.

Wine API directories:
---------------------

KERNEL:

        files/                  - file I/O
        loader/                 - Win16-, Win32-binary loader
        memory/                 - memory management
        msdos/                  - DOS features and BIOS calls (interrupts)
        scheduler/              - process and thread management

GDI:

        graphics/               - graphics drivers
                x11drv/         - X11 display driver
                win16drv/       -> see below 
                ttydrv/         - tty display driver
                psdrv/          - PostScript graphics driver
                metafiledrv/    - metafile driver
                enhmetafiledrv/ - enhanced metafile driver
        objects/                - logical objects

USER:

        controls/               - built-in widgets
        resources/              - built-in menu and message box resources
        windows/                - window management

Other DLLs:

        dlls/                   - Other system DLLs implemented by Wine
                advapi32/       - crypto, systeminfo, security, eventlogging
                avifil32/       - COM object to play AVI files
                comctl32/       - common controls
                commdlg/        - common dialog boxes (both 16 & 32 bit)
                dplayx/         - DirectX dplayx
                dsound/         - DirectX dsound
                imagehlp/       - PE (Portable Executable) Image Helper lib
                imm32/
                lzexpand/       - Liv-Zempel compression/decompression
                mpr/            - Multi-Protocol Router (interface to various 
                                  network transport protocols)
                msacm/          - audio compression manager (multimedia) (16 bit)
                msacm32/        - audio compression manager (multimedia) (32 bit)
                msnet/
                msvideo/        - 16 bit video manager
                ole32/          - 32 bit OLE 2.0 librairies
                oleaut32/       - 32 bit OLE 2.0 automation
                olecli/         - 16 bit OLE client
                oledlg/         - OLE 2.0 user interface support
                olesvr/         - 16 bit OLE server
                ntdll/          - NT implementation of kernel calls
                psapi/          - process status API
                rasapi32/       - remote access server API
                shell32/        - COM object implementing shell views
                sound/          - Sound on loudspeaker (not sound card)
                tapi32/         - telephone API
                ver/            - File Installation Library (16 bit)
                version/        - File Installation Library (32 bit)
                win32s
                win87em         - 80387 math-emulation
                winaspi/        - 16 bit Advanced SCSI Peripheral Interface
                windebug/       - Windows debugger
                wing/           - WinG (for games) internface
                winmm/          - multimedia (16 & 32 bit)
                        mciXXX/ - various MCI drivers
                        wineoss/- MM driver for OSS systems
                        wavemap/- audio mapper
                        midimap/- midi mapper
                winspool/       - Printing & Print Spooler 
                wnaspi32/       - 32 bit ASPI

Miscellaneous:

        misc/                   - shell, registry, winsock, etc.
        ipc/                    - SysV IPC based interprocess communication
        win32/                  - misc Win32 functions
        ole/                    - OLE code 
                nls/            - National Language Support 
                                  configuration files

Tools:
------

        rc/                     - old resource compiler
        tools/                  - relay code builder, new rc, bugreport
                                  generator, wineconfigurator, etc.
        documentation/          - some documentation


Binary loader specific directories:
-----------------------------------

        debugger/               - built-in debugger
        if1632/                 - relay code
        miscemu/                - hardware instruction emulation
        graphics/win16drv/      - Win16 printer driver
        server/                 - the main, controlling thread of wine
        tsx11/                  - thread-safe X11 wrappers (auto generated)

Winelib specific directories:
-----------------------------

        library/                - Required code for programs using Winelib
        libtest/                - Small samples and tests
        programs/               - Extended samples / system utilities


IMPLEMENTING NEW API CALLS
==========================

This is the simple version, and covers only Win32. Win16 is slightly uglier,
because of the Pascal heritage and the segmented memory model.

All of the Win32 APIs known to Wine are listed in [relay32/*.spec]. An
unimplemented call will look like (from gdi32.spec)
  269 stub PolyBezierTo
To implement this call, you need to do the following four things.

1. Find the appropriate parameters for the call, and add a prototype to
the correct header file. In this case, that means [include/wingdi.h],
and it might look like
  BOOL WINAPI PolyBezierTo(HDC, LPCVOID, DWORD);
If the function has both an ASCII and a Unicode version, you need to
define both and add a #define WINELIB_NAME_AW declaration. See below
for discussion of function naming conventions.
  
2. Modify the .spec file to tell Wine that the function has an
implementation, what the parameters look like and what Wine function
to use for the implementation. In Win32, things are simple--everything
is 32-bits. However, the relay code handles pointers and pointers to
strings slightly differently, so you should use 'str' and 'wstr' for
strings, 'ptr' for other pointer types, and 'long' for everything else.
  269 stdcall PolyBezierTo(long ptr long) PolyBezierTo
The 'PolyBezierTo' at the end of the line is which Wine function to use
for the implementation.

3. Implement the function as a stub. Once you add the function to the .spec
file, you must add the function to the Wine source before it will link.
Add a function called 'PolyBezierTo' somewhere. Good things to put
into a stub:
  o a correct prototype, including the WINAPI
  o header comments, including full documentation for the function and
    arguments (see documentation/README.documentation)
  o A FIXME message and an appropriate return value are good things to
    put in a stub.

  /************************************************************
   *                    PolyBezierTo   (GDI32.269)  
   *  
   * Draw many Bezier curves
   *
   * RETURNS
   *   nonzero on success or zero on faillure
   *
   * BUGS
   *   Unimplemented
   */
   BOOL WINAPI PolyBezierTo(HDC hdc,     /* handle to device context */
                            LPCVOID p,   /* ptr to array of Point structs */
                            DWORD count  /* nr of points in array */
   ) 
   {
      /* tell the user they've got a substandard implementation */
      FIXME(gdi, ":(%x,%p,%d): stub\n", hdc, p, count);

      /* some programs may be able to compensate, 
       * if they know what happened 
       */
      SetLastError(ERROR_CALL_NOT_IMPLEMENTED);  
      return FALSE;    /* error value */
   }

4. Implement and test the rest of the function.


IMPLEMENTING A NEW DLL
======================

Generic directions
------------------

Apart from writing the set of needed .c files, you also need to do the 
following:

1.  Create a directory <MyDll> where to store the implementation of
    the DLL. 

    If the DLL exists under Windows as both 16 and 32 bit DLL, you can
    either create one directory for each, or have a single directory
    with both implementations. 

    This (those) directory(ies) have to be put under the dlls/
    directory in Wine tree structure.

2.  Create the Makefile.in in the ./dlls/<MyDll>/ directory. You can
    copy an existing Makefile.in from another ./dlls/ subdirectory.

    You need at least to change the MODULE, SPEC_SRCS, and C_SRCS
    macros. 

3.  Add the directory (and the generated .o file for the module) in: 
    + ./configure.in (in AC_OUTPUT macro at the end of the file to
      trigger the Makefile generation),
    + ./Makefile.in (in LIBSUBDIRS and LIBOBJS macros)
    + ./dlls/Makefile.in (in SUBDIRS macro)

4.  You can now regenerate ./configure file (with 'make configure')
    and the various Makefiles (with 'configure; make depend') (run
    from the top of Wine's tree).

    You shall now have a Makefile file in ./dlls/<MyDll>/

5.  You now need to declare the DLL in the module lists. This is done
    by adding the corresponding descriptor in ./if1632/builtin.c if
    your DLL is 16 bit (resp. ./relay32/builtin.c for a 32 bit DLL)
    (or both if your directory contains the dual 16/32
    implementations). 

    Note: the name of the descriptor is based on the module name, not
    on the file name (they are the same in most of the case, but for
    some DLLs it's not the case).

6.  You also need to define the loadorder for the created DLL
    (./wine.ini and ./loader/loadorder.c). Usually, "native,builtin"
    is ok. If you have written a paired 16/32 bit implementation, don't
    forget to define it also in those files. 

7.  Create the .spec file for the DLL export points in your
    directory. Refer to 'Implementation of new API calls' earlier in
    this document for more information on this part.

8.  Don't forget the .cvsignore file. The .cvsignore contain (on a per
    directory basis) all the files generated by the compilation
    process, why cvs shall ignore when processing the dir. 
    *.o is in there by default, but in Wine case you will find:
    - Makefile (generated from Makefile.in)
    - *.spec.c: those c files are generated by tools/build from the
      .spec file
    - when thunking down to 16 bit DLLs, you'll get some others (.glue.c)
    - result of .y => .c translation (by yacc or bison)
    - result of .rc compilation
    - ...
    For a simple DLL, listing in .cvsignore Makefile and
    <MyDll>.spec.c will do. 

9.  You can now start adding .c files.

10. For the .h files, if they are standard Windows one, put them in
    include/. If they are linked to *your* implementation of the DLL,
    put them in your newly created directory.

Debug channels
--------------

If you need to create a new debug channel, just add the
DECLARE_DEBUG_CHANNEL to your .c file(s) and rerun
tools/make_debug. When sending out your patch, you don't need to
provide nor ./configure nor the ./include/debugdefs.h diffs. Just
indicate that those files need to be regenerated.

Resources
---------

If you also need to add resources to your DLL, the create the .rc
file. Since, the .rc file will be translated into a .s file, and then
compiled as a .o file, its basename must be different from the
basename of any .c file.
Add to your ./dlls/<MyDll>/Makefile.in, in the RC_SRCS macro, the list 
of .rc files to add to the DLL. You may also have to add the following
directives
1/ to tell gnumake to translate .rc into .s files,
        $(RC_SRCS:.rc=.s): $(WRC)
2/ to give some parameters to wrc for helping the translation.
        WRCEXTRA  = -s -p$(MODULE)

See dlls/comctl32/ for an example of this.

Thunking
--------

If you're building a 16 & 32 bit DLLs pair, then from the 32 bit code
you might need to call 16 bit routine. The way to do it to add in the
code, fragments like:
/* ### Start build ### */
extern WORD CALLBACK <PREFIX>_CallTo16_word_wwlll(FARPROC16,WORD,WORD,LONG,LONG,LONG);
/* ### stop build ### */
Where <PREFIX>_ is an internal prefix for your module. The first
parameter is always of type FARPROC16. Then, you can get the regular
list of parameters. The _word_wwlll indicates the type of return (long
or word) and the size of the parameters (here l=>long, w=>word; which
maps to WORD,WORD,LONG,LONG,LONG.
You can put several functions between the Start/Stop build pair.

You can also read tools/build.txt for more details on this.

Then, add to ./dlls/<MyDll>/Makefile.in to the macro GLUE the list of
.c files containing the /* ### Start build ### */ directives.

See dlls/winmm/ for an example of this.

MEMORY AND SEGMENTS
===================

NE (Win16) executables consist of multiple segments.  The Wine loader
loads each segment into a unique location in the Wine processes memory
and assigns a selector to that segment.  Because of this, it's not
possible to exchange addresses freely between 16-bit and 32-bit code.
Addresses used by 16-bit code are segmented addresses (16:16), formed
by a 16-bit selector and a 16-bit offset.  Those used by the Wine code
are regular 32-bit linear addresses.

There are four ways to obtain a segmented pointer:
  - Use the SEGPTR_* macros in include/heap.h (recommended).
  - Allocate a block of memory from the global heap and use
    WIN16_GlobalLock to get its segmented address.
  - Allocate a block of memory from a local heap, and build the
    segmented address from the local heap selector (see the
    USER_HEAP_* macros for an example of this).
  - Declare the argument as 'segptr' instead of 'ptr' in the spec file
    for a given API function.

Once you have a segmented pointer, it must be converted to a linear
pointer before you can use it from 32-bit code.  This can be done with
the PTR_SEG_TO_LIN() and PTR_SEG_OFF_TO_LIN() macros.  The linear
pointer can then be used freely with standard Unix functions like
memcpy() etc. without worrying about 64k boundaries.  Note: there's no
easy way to convert back from a linear to a segmented address.

In most cases, you don't need to worry about segmented address, as the
conversion is made automatically by the callback code and the API
functions only see linear addresses. However, in some cases it is
necessary to manipulate segmented addresses; the most frequent cases
are:
  - API functions that return a pointer
  - lParam of Windows messages that point to a structure
  - Pointers contained inside structures accessed by 16-bit code.

It is usually a good practice to used the type 'SEGPTR' for segmented
pointers, instead of something like 'LPSTR' or 'char *'.  As SEGPTR is
defined as a DWORD, you'll get a compilation warning if you mistakenly
use it as a regular 32-bit pointer.


STRUCTURE PACKING
=================

Under Windows, data structures are tightly packed, i.e. there is no
padding between structure members. On the other hand, by default gcc
aligns structure members (e.g. WORDs are on a WORD boundary, etc.).
This means that a structure like

struct { BYTE x; WORD y; };

will take 3 bytes under Windows, but 4 with gcc, because gcc will add a
dummy byte between x and y. To have the correct layout for structures
used by Windows code, you need to embed the struct within two special
#include's which will take care of the packing for you:

#include "pshpack1.h"
struct { BYTE x; WORD y; };
#include "poppack1.h"

For alignment on a 2-byte boundary, there is a "pshpack2.h", etc.

The use of the WINE_PACKED attribute is obsolete. Please remove these 
in favour of the above solution. 
Using WINE_PACKED, you would declare the above structure like this:

struct { BYTE x; WORD y WINE_PACKED; };

You had to do this every time a structure member is not aligned
correctly under Windows (i.e. a WORD not on an even address, or a
DWORD on a address that was not a multiple of 4).


NAMING CONVENTIONS FOR API FUNCTIONS AND TYPES
==============================================

In order to support both Win16 and Win32 APIs within the same source
code, the following convention must be used in naming all API
functions and types. If the Windows API uses the name 'xxx', the Wine
code must use:

 - 'xxx16' for the Win16 version,
 - 'xxx'   for the Win32 version when no ASCII/Unicode strings are
   involved,
 - 'xxxA'  for the Win32 version with ASCII strings,
 - 'xxxW'  for the Win32 version with Unicode strings.

If the function has both ASCII and Unicode version, you should then
use the macros WINELIB_NAME_AW(xxx) or DECL_WINELIB_TYPE_AW(xxx)
(defined in include/windef.h) to define the correct 'xxx' function
or type for Winelib. When compiling Wine itself, 'xxx' is _not_
defined, meaning that code inside of Wine must always specify
explicitly the ASCII or Unicode version.

If 'xxx' is the same in Win16 and Win32, you can simply use the same
name as Windows, i.e. just 'xxx'.  If 'xxx' is Win16 only, you could
use the name as is, but it's preferable to use 'xxx16' to make it
clear it is a Win16 function.

Examples:

typedef struct { /* Win32 ASCII data structure */ } WNDCLASSA;
typedef struct { /* Win32 Unicode data structure */ } WNDCLASSW;
typedef struct { /* Win16 data structure */ } WNDCLASS16;
DECL_WINELIB_TYPE_AW(WNDCLASS);

ATOM RegisterClass16( WNDCLASS16 * );
ATOM RegisterClassA( WNDCLASSA * );
ATOM RegisterClassW( WNDCLASSW * );
#define RegisterClass WINELIB_NAME_AW(RegisterClass)

The Winelib user can then say:

    WNDCLASS wc = { ... };
    RegisterClass( &wc );

and this will use the correct declaration depending on the definition
of the UNICODE symbol.


NAMING CONVENTIONS FOR NON-API FUNCTIONS AND TYPES
==================================================

Functions and data which are internal to your code (or at least shouldn't be
visible to any WineLib or Windows program) should be preceded by
an identifier to the module:

Examples:

ENUMPRINTERS_GetDWORDFromRegistryA()    (in dlls/winspool/info.c)
IAVIFile_fnRelease()                    (in dlls/avifil32/avifile.c)
X11DRV_CreateDC()                       (in graphics/x11drv/init.c)
TIMER_Init()                            (implemented in windows/timer.c,
                                         used in loader/main.c )

if you need prototypes for these, there are a few possibilities:
- within same source file only:
  put the prototypes at the top of your file and mark them as prototypes.
- within the same module:
  create a header file within the subdirectory where that module resides,
  e.g.  graphics/ddraw_private.h
- from a totally different module, or for use in winelib:
  put your header file entry in /include/wine/
  but be careful not to clutter this directory!
under no circumstances, you should add non-api calls to the standard
windoze include files. Unfortunately, this is often the case, e.g.
the above example of TIMER_Init is defined in include/message.h


API ENTRY POINTS
================

Because Win16 programs use a 16-bit stack and because they can only
call 16:16 addressed functions, all API entry points must be at low
address offsets and must have the arguments translated and moved to
Wines 32-bit stack.  This task is handled by the code in the "if1632"
directory.  To define a new API entry point handler you must place a
new entry in the appropriate API specification file.  These files are
named *.spec.  For example, the API specification file for the USER
DLL is contained in the file user.spec.  These entries are processed
by the "build" program to create an assembly file containing the entry
point code for each API call.  The format of the *.spec files is
documented in the file "tools/build-spec.txt".


DEBUG MESSAGES
==============

To display a message only during debugging, you normally write something
like this:

        TRACE(win,"abc...");  or
        FIXME(win,"abc...");  or
        WARN(win,"abc...");   or
        ERR(win,"abc...");

depending on the seriousness of the problem. (documentation/degug-msgs
explains when it is appropriate to use each of them)

These macros are defined in include/debug.h. The macro-definitions are
generated by the shell-script tools/make_debug. It scans the source
code for symbols of this forms and puts the necessary macro
definitions in include/debug.h and include/debugdefs.h. These macros
test whether the debugging "channel" associated with the first
argument of these macros (win in the above example) is enabled and
thus decide whether to actually display the text.  In addition you can
change the types of displayed messages by supplying the "-debugmsg"
option to Wine.  If your debugging code is more complex than just
printf, you can use the symbols TRACE_ON(xxx), WARN_ON(xxx),
ERR_ON(xxx) and FIXME_ON(xxx) as well. These are true when channel xxx
is enabled, either permanent or in the command line. Thus, you can
write:

        if(TRACE_ON(win))DumpSomeStructure(&str);

Don't worry about the inefficiency of the test. If it is permanently 
disabled (that is TRACE_ON(win) is 0 at compile time), the compiler will 
eliminate the dead code.

You have to start tools/make_debug only if you introduced a new macro,
e.g.  TRACE(win32).

For more info about debugging messages, read:

documentation/debug-msgs


MORE INFO
=========

1. There is a FREE online version of the MSDN library (including
   documentation for the Win32 API) on http://www.microsoft.com/msdn/

2. http://www.sonic.net/~undoc/bookstore.html

3. In 1993 Dr. Dobbs Journal published a column called "Undocumented Corner".

4. You might want to check out BYTE from December 1983 as well :-)