OpenGL documentation.
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Lionel Ulmer
Alexandre Julliard
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I What is needed to have OpenGL support in Wine
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===============================================
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Basically, if you have a Linux OpenGL ABI compliant libGL
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(http://oss.sgi.com/projects/ogl-sample/ABI/) installed on your
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computer, you should everything that is needed.
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To be more clear, I will detail one step after another what the
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configure script checks.
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If, after Wine compiles, OpenGL support is not compiled in, you can
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always check 'config.log' to see which of the following points failed.
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I.1 Header files
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----------------
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The needed header files to build OpenGL support in Wine are :
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- gl.h : the definition of all OpenGL core functions, types and
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enumerants
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- glx.h : how OpenGL integrates in the X Window environment
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- glext.h : the list of all registered OpenGL extensions
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The latter file (glext.h) is, as of now, not necessary to build
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Wine. But as this file can be easily obtained from SGI
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(http://oss.sgi.com/projects/ogl-sample/ABI/glext.h), and that all
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OpenGL should provide one, I decided to keep it here.
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I.2 OpenGL library thread-safety
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--------------------------------
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After that, the script checks if the OpenGL library relies or not on
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the pthread library to provide thread safety (most 'modern' OpenGL
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libraries do).
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If the OpenGL library explicitely links in libpthread (you can check
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it with a 'ldd libGL.so'), you need to force OpenGL support by
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starting configure with the '--enable-opengl' flag.
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The reason to this is that Wine contains some hacks done by Ove to
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cohabit with pthread that are known to work well in most of the cases
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(glibc 2.1.x). On the other hand, we never got Wine to work with glibc
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2.0.6. Thus, I deemed preferable to play it safe : by default, I
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suppose that the hack won't work and that it's the user's
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responsability to enable it.
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Anyway, it should be pretty safe to build with '--enable-opengl'.
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I.3 OpenGL library itself
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-------------------------
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To check for the presence of 'libGL' on the system, the script checks
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if it defines the 'glXCreateContext' function. There should be no
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problem here.
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I.4 glXGetProcAddressARB function
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---------------------------------
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The core of Wine's OpenGL implementation (at least for all extensions)
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is the glXGetProcAddressARB function. Your OpenGL library needs to
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have this function defined for Wine to be able to support OpenGL.
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If your library does not provide it, you are out of luck.
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(Note: this is not completely true as one could rewrite a
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glXGetProcAddressARB replacement using 'dlopen' and friends,
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but well, telling people to upgrade is easier :-) ).
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II How to configure
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===================
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Configuration is quite easy : once OpenGL support has been built in
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Wine, this internal OpenGL driver will be used each time an
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application tries to load 'opengl32.dll'.
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Due to restrictions (that do not exist in Windows) on OpenGL contexts,
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if you want to prevent the screen to flicker when using OpenGL
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applications (all games are using double-buffered contexts), you need
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to set the following option in your .winerc / wine.ini in the [x11drv]
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section :
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DesktopDoubleBuffered = Y
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and to run Wine with the '--desktop' option.
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III How it all works
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====================
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(to be done later)
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IV Known problems - shortcomings
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=================================
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IV.1 Missing GLU32.DLL
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----------------------
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GLU is a library that is layered upon OpenGL. There is a 100 %
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corespondance between the libGLU.so that is used on Linux and
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GLU32.DLL.
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As for the moment, I did not create a set of thunks to support this
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library natively in Wine (it would easy to do, but I am waiting for a
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better solution than adding another autogenerated thunk file), you can
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always download anywhere on the net (it's free) a GLU32.DLL file (by
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browsing, for example, http://ftpsearch.lycos.com/).
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IV.2 OpenGL not detected at configure time
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------------------------------------------
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See section (I) for a detailed explanation of the configure
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requirements.
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IV.3 When running an OpenGL application, the screen flickers
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------------------------------------------------------------
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See section (II) for how to create the context double-buffered and
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thus preventing this flicker effect.
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IV.4 Wine gives me the following error message :
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------------------------------------------------
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Extension defined in the OpenGL library but NOT in opengl_ext.c... Please report
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(lionel.ulmer@free.fr) !
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This means that the extension requested by the application is found in
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the libGL used by Linux (ie the call to glXGetProcAddressARB returns a
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non NULL pointer) but that this string was NOT found in Wine's
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extension registry.
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This can come from two causes :
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- the opengl_ext.c file is too old and need to be generated again.
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- use of obsolete extensions that are not supported anymore by SGI or
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of 'private' extensions that are not registered. An example of the
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former are 'glMTexCoord2fSGIS' and 'glSelectTextureSGIS' as used by
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Quake 2 (and apparently also by old versions of Half Life). If
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documentation can be found on these functions, they can be added to
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Wine's extension set.
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If you have this, run with --debugmsg +opengl and send me
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(lionel.ulmer@free.fr) the TRACE.
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Lionel Ulmer (lionel.ulmer@free.fr)
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last modification : 2000/06/12
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