From d0dfcde4fbbcd42d948366af13ad55c3ec02d6bb Mon Sep 17 00:00:00 2001 From: Lionel Ulmer Date: Wed, 14 Jun 2000 21:15:38 +0000 Subject: [PATCH] Updated OpenGL documentation. --- documentation/opengl | 116 +++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 113 insertions(+), 3 deletions(-) diff --git a/documentation/opengl b/documentation/opengl index 647dde46942..49df0b80470 100644 --- a/documentation/opengl +++ b/documentation/opengl @@ -95,7 +95,91 @@ and to run Wine with the '--desktop' option. III How it all works ==================== -(to be done later) +The core OpenGL function calls are the same between Windows and +Linux. So what is the difficulty to support it in Wine ? Well, there +is two different problems : + + - 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). + + - 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 braindead programs (using GL calls without setting-up +a context or deleting three time the same context) and you have still +some work to do :-) + + +III.1 The Windowing system integration +-------------------------------------- + +This integration is done at two levels : + + - 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 'graphics/x11drv/opengl.c' (all these functions are + part of Wine's graphic driver function pointer table and thus could + be reimplented if ever Wine works on another Windowing system than + X). + + - in the OpenGL32.DLL itself for all other functionalities (context + creation / deletion, querying of extension functions, ...). This is + done in 'dlls/opengl32/wgl.c'. + + +III.2 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 +CVS 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 two arguments : + + - the first is the path to the OpenGL registry. Now, you will all ask + 'but what is the OpenGL registry ?' :-) Well, it's part of the + OpenGL sample implementation source tree from SGI (more + informations at this URL : http://oss.sgi.com/projects/ogl-sample/). + + To summarize, these files contains human-readable but easily parsed + informations on ALL OpenGL core functions and ALL registered + extensions (for example the prototype, the OpenGL version, ...). + + - the second is the OpenGL 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. Windows is + based, for now, on OpenGL 1.1, but the thunks that are in the CVS + tree are generated for OpenGL 1.2. + + This option can have three values '1.0', '1.1' and '1.2'. + +This script generates three files : + + - 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. + + - 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. + + - 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. @@ -155,6 +239,32 @@ If you have this, run with --debugmsg +opengl and send me (lionel.ulmer@free.fr) the TRACE. +IV.5 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 : + + - create a dummy .c file : + +int main(void) { + return 0; +} + + - 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 + + - 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). + + - Lionel Ulmer (lionel.ulmer@free.fr) - last modification : 2000/06/12 + Lionel Ulmer (lionel.ulmer@free.fr) + last modification : 2000/06/13 -- 2.11.4.GIT