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368 lines
13 KiB
Text
368 lines
13 KiB
Text
<chapter id="opengl">
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<title>Wine and OpenGL</title>
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<sect1 id="opengl-required">
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<title>What is needed to have OpenGL support in Wine</title>
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<para>
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Basically, if you have a Linux OpenGL ABI compliant libGL
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(<ulink url="http://oss.sgi.com/projects/ogl-sample/ABI/">
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http://oss.sgi.com/projects/ogl-sample/ABI/</ulink>)
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installed on your computer, you should have everything
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that is needed.
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</para>
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<para>
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To be more clear, I will detail one step after another what
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the <command>configure</command> script checks.
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</para>
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<para>
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If, after Wine compiles, OpenGL support is not compiled in,
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you can always check <filename>config.log</filename> to see
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which of the following points failed.
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</para>
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<sect2>
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<title>Header files</title>
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<para>
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The needed header files to build OpenGL support in Wine are :
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</para>
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<variablelist>
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<varlistentry>
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<term><filename>gl.h:</filename></term>
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<listitem>
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<para>
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the definition of all OpenGL core functions, types and enumerants
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>glx.h:</filename></term>
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<listitem>
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<para>
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how OpenGL integrates in the X Window environment
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><filename>glext.h:</filename></term>
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<listitem>
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<para>
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the list of all registered OpenGL extensions
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>
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The latter file (<filename>glext.h</filename>) is, as of
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now, not necessary to build Wine. But as this file can be
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easily obtained from SGI
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(<ulink url="http://oss.sgi.com/projects/ogl-sample/ABI/glext.h">
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http://oss.sgi.com/projects/ogl-sample/ABI/glext.h</ulink>),
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and that all OpenGL should provide one, I decided to keep it here.
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</para>
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</sect2>
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<sect2>
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<title>OpenGL library itself</title>
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<para>
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To check for the presence of 'libGL' on the system, the
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script checks if it defines the
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<function>glXCreateContext</function> function.
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</para>
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</sect2>
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<sect2>
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<title>glXGetProcAddressARB function</title>
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<para>
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The core of Wine's OpenGL implementation (at least for all
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extensions) is the <function>glXGetProcAddressARB</function>
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function. Your OpenGL library needs to have this function
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defined for Wine to be able to support OpenGL.
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</para>
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</sect2>
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</sect1>
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<sect1 id="opengl-works">
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<title>How it all works</title>
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<para>
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The core OpenGL function calls are the same between Windows
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and Linux. So what is the difficulty to support it in Wine ?
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Well, there are two different problems :
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</para>
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<orderedlist>
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<listitem>
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<para>
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the interface to the windowing system is different for
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each OS. It's called 'GLX' for Linux (well, for X Window)
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and 'wgl' for Windows. Thus, one need first to emulate one
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(wgl) with the other (GLX).
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</para>
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</listitem>
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<listitem>
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<para>
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the calling convention between Windows (the 'Pascal'
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convention or 'stdcall') is different from the one used on
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Linux (the 'C' convention or 'cdecl'). This means that
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each call to an OpenGL function must be 'translated' and
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cannot be used directly by the Windows program.
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</para>
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</listitem>
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</orderedlist>
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<para>
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Add to this some brain-dead programs (using GL calls without
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setting-up a context or deleting three time the same context)
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and you have still some work to do :-)
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</para>
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<sect2>
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<title>The Windowing system integration</title>
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<para>
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This integration is done at two levels :
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</para>
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<orderedlist>
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<listitem>
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<para>
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At GDI level for all pixel format selection routines (ie
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choosing if one wants a depth / alpha buffer, the size
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of these buffers, ...) and to do the 'page flipping' in
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double buffer mode. This is implemented in
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<filename>dlls/x11drv/opengl.c</filename> (all these
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functions are part of Wine's graphic driver function
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pointer table and thus could be reimplemented if ever Wine
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works on another Windowing system than X).
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</para>
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</listitem>
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<listitem>
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<para>
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In the <filename>OpenGL32.DLL</filename> itself for all
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other functionalities (context creation / deletion,
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querying of extension functions, ...). This is done in
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<filename>dlls/opengl32/wgl.c</filename>.
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</para>
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</listitem>
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</orderedlist>
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</sect2>
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<sect2>
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<title>The thunks</title>
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<para>
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The thunks are the Wine code that does the calling
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convention translation and they are auto-generated by a Perl
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script. In Wine's CVS tree, these thunks are already
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generated for you. Now, if you want to do it yourself, there
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is how it all works....
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</para>
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<para>
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The script is located in <filename>dlls/opengl32</filename>
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and is called <command>make_opengl</command>. It requires
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Perl5 to work and takes two arguments :
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</para>
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<orderedlist>
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<listitem>
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<para>
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The first is the path to the OpenGL registry. Now, you
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will all ask 'but what is the OpenGL registry ?' :-)
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Well, it's part of the OpenGL sample implementation
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source tree from SGI (more informations at this URL :
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<ulink url="http://oss.sgi.com/projects/ogl-sample/">
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http://oss.sgi.com/projects/ogl-sample/</ulink>.
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</para>
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<para>
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To summarize, these files contain human-readable but
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easily parsed information on ALL OpenGL core functions
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and ALL registered extensions (for example the
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prototype, the OpenGL version, ...).
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</para>
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</listitem>
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<listitem>
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<para>
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the second is the OpenGL version to 'simulate'. This
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fixes the list of functions that the Windows application
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can link directly to without having to query them from
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the OpenGL driver. Windows is based, for now, on OpenGL
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1.1, but the thunks that are in the CVS tree are
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generated for OpenGL 1.2.
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</para>
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<para>
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This option can have three values:
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<literal>1.0</literal>, <literal>1.1</literal> and
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<literal>1.2</literal>.
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</para>
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</listitem>
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</orderedlist>
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<para>
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This script generates three files :
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</para>
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<orderedlist>
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<listitem>
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<para>
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<filename>opengl32.spec</filename> gives Wine's linker
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the signature of all function in the
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<filename>OpenGL32.DLL</filename> library so that the
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application can link them. Only 'core' functions are
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listed here.
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</para>
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</listitem>
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<listitem>
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<para>
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<filename>opengl_norm.c</filename> contains all the
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thunks for the 'core' functions. Your OpenGL library
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must provide ALL the function used in this file as these
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are not queried at run time.
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</para>
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</listitem>
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<listitem>
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<para>
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<filename>opengl_ext.c</filename> contains all the
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functions that are not part of the 'core' functions.
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Contrary to the thunks in
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<filename>opengl_norm.c</filename>, these functions do
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not depend at all on what your libGL provides.
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</para>
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<para>
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In fact, before using one of these thunks, the Windows
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program first needs to 'query' the function pointer. At
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this point, the corresponding thunk is useless. But as
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we first query the same function in libGL and store the
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returned function pointer in the thunk, the latter
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becomes functional.
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</para>
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</listitem>
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</orderedlist>
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</sect2>
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</sect1>
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<sect1 id="opengl-problems">
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<title>Known problems</title>
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<sect2>
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<title>When running an OpenGL application, the screen flickers</title>
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<para>
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Due to restrictions (that do not exist in Windows) on OpenGL
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contexts, if you want to prevent the screen to flicker when
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using OpenGL applications (all games are using double-buffered
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contexts), you need to set the following option in your
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<filename>~/.wine/config</filename> file
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in the <literal>[x11drv]</literal> section:
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<programlisting>
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DesktopDoubleBuffered = Y
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</programlisting>
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and to run Wine in desktop mode.
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</para>
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</sect2>
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<sect2>
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<title>Unknown extension error message:</title>
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<screen>
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Extension defined in the OpenGL library but NOT in opengl_ext.c...
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Please report (lionel.ulmer@free.fr) !
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</screen>
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<para>
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This means that the extension requested by the application
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is found in the libGL used by Linux (ie the call to
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<function>glXGetProcAddressARB</function> returns a
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non-<constant>NULL</constant> pointer) but that this string
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was NOT found in Wine's extension registry.
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</para>
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<para>
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This can come from two causes:
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<orderedlist>
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<listitem>
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<para>
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The <filename>opengl_ext.c</filename> file is too old
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and needs to be generated again.
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</para>
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</listitem>
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<listitem>
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<para>
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Use of obsolete extensions that are not supported
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anymore by SGI or of 'private' extensions that are not
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registered. An example of the former are
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<function>glMTexCoord2fSGIS</function> and
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<function>glSelectTextureSGIS</function> as used by
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Quake 2 (and apparently also by old versions of Half
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Life). If documentation can be found on these functions,
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they can be added to Wine's extension set.
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</para>
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</listitem>
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</orderedlist>
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</para>
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<para>
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If you have this, run with <parameter>WINEDEBUG=+opengl</parameter>
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and send me <email>lionel.ulmer@free.fr</email> the TRACE.
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</para>
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</sect2>
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<sect2>
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<title><filename>libopengl32.so</filename> is built but it is still not working</title>
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<para>
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This may be caused by some missing functions required by
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<filename>opengl_norm.c</filename> but that your Linux
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OpenGL library does not provide.
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</para>
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<para>
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To check for this, do the following steps :
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</para>
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<orderedlist>
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<listitem>
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<para>
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create a dummy <filename>.c</filename> file :
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</para>
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<programlisting>
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int main(void)
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{
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return 0;
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}
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</programlisting>
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</listitem>
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<listitem>
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<para>
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try to compile it by linking both libwine and
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libopengl32 (this command line supposes that you
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installed the Wine libraries in
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<filename>/usr/local/lib</filename>, YMMV) :
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</para>
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<programlisting>
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gcc dummy.c -L/usr/local/lib -lwine -lopengl32
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</programlisting>
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</listitem>
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<listitem>
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<para>
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if it works, the problem is somewhere else (and you can
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send me an email). If not, you could re-generate the
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thunk files for OpenGL 1.1 for example (and send me your
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OpenGL version so that this problem can be detected at
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configure time).
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</para>
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</listitem>
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</orderedlist>
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</sect2>
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</sect1>
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</chapter>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-parent-document:("wine-devel.sgml" "set" "book" "part" "chapter" "")
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End:
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-->
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