<H1>Environment Variables</H1>
<p>
-Mesa supports the following environment variables:
+Normally, no environment variables need to be set. Most of the environment
+variables used by Mesa/Gallium are for debugging purposes, but they can
+sometimes be useful for debugging end-user issues.
</p>
+
+
+<H2>LibGL environment variables</H2>
+
+<ul>
+<li>LIBGL_DEBUG - If defined debug information will be printed to stderr.
+ If set to 'verbose' additional information will be printed.
+<li>LIBGL_DRIVERS_PATH - colon-separated list of paths to search for DRI drivers
+<li>LIBGL_ALWAYS_INDIRECT - forces an indirect rendering context/connection.
+<li>LIBGL_ALWAYS_SOFTWARE - if set, always use software rendering
+<li>LIBGL_NO_DRAWARRAYS - if set do not use DrawArrays GLX protocol (for debugging)
+</ul>
+
+
+
+<H2>Core Mesa environment variables</H2>
+
<ul>
<li>MESA_NO_ASM - if set, disables all assembly language optimizations
<li>MESA_NO_MMX - if set, disables Intel MMX optimizations
<li>MESA_NO_3DNOW - if set, disables AMD 3DNow! optimizations
<li>MESA_NO_SSE - if set, disables Intel SSE optimizations
-<li>MESA_DEBUG - if set, error messages are printed to stderr.
-If the value of MESA_DEBUG is "FP" floating point arithmetic errors will
-generate exceptions.
-<li>MESA_NO_DITHER - if set, disables dithering, overriding glEnable(GL_DITHER)
+<li>MESA_DEBUG - if set, error messages are printed to stderr. For example,
+ if the application generates a GL_INVALID_ENUM error, a corresponding error
+ message indicating where the error occured, and possibly why, will be
+ printed to stderr.<br>
+ If the value of MESA_DEBUG is 'FP' floating point arithmetic errors will
+ generate exceptions.
<li>MESA_TEX_PROG - if set, implement conventional texture env modes with
fragment programs (intended for developers only)
<li>MESA_TNL_PROG - if set, implement conventional vertex transformation
<li>MESA_EXTENSION_OVERRIDE - can be used to enable/disable extensions.
A value such as "GL_EXT_foo -GL_EXT_bar" will enable the GL_EXT_foo extension
and disable the GL_EXT_bar extension.
-<li>MESA_GLSL - <a href="shading.html#envvars">shading language options</a>
+<li>MESA_EXTENSION_MAX_YEAR - The GL_EXTENSIONS string returned by Mesa is sorted
+by extension year.
+If this variable is set to year X, only extensions defined on or before year
+X will be reported.
+This is to work-around a bug in some games where the extension string is
+copied into a fixed-size buffer without truncating.
+If the extension string is too long, the buffer overrun can cause the game
+to crash.
+This is a work-around for that.
+<li>MESA_GL_VERSION_OVERRIDE - changes the value returned by
+glGetString(GL_VERSION). Valid values are point-separated version numbers,
+such as "3.0". Mesa will not really implement all the features of the given
+version if it's higher than what's normally reported.
+<li>MESA_GLSL_VERSION_OVERRIDE - changes the value returned by
+glGetString(GL_SHADING_LANGUAGE_VERSION). Valid values are integers, such as
+"130". Mesa will not really implement all the features of the given language version
+if it's higher than what's normally reported. (for developers only)
+<li>MESA_GLSL - <a href="shading.html#envvars">shading language compiler options</a>
</ul>
+
+<H2>Mesa Xlib driver environment variables</H2>
+
<p>
-The following are only applicable to the Xlib software driver.
+The following are only applicable to the Mesa Xlib software driver.
See the <A HREF="xlibdriver.html">Xlib software driver page</A> for details.
</p>
<ul>
<li>MESA_GAMMA - gamma correction coefficients for red, green, blue channels
<li>MESA_XSYNC - enable synchronous X behavior (for debugging only)
<li>MESA_GLX_FORCE_CI - if set, force GLX to treat 8bpp visuals as CI visuals
-<li>MESA_GLX_FX - set to either "fullscreen" for full-screen rendering,
- "window" to render into a window, or "disable" to disable the Glide driver.
<li>MESA_GLX_FORCE_ALPHA - if set, forces RGB windows to have an alpha channel.
<li>MESA_GLX_DEPTH_BITS - specifies default number of bits for depth buffer.
<li>MESA_GLX_ALPHA_BITS - specifies default number of bits for alpha channel.
</ul>
+<h2>i945/i965 driver environment variables (non-Gallium)</h2>
+
+<ul>
+<li>INTEL_STRICT_CONFORMANCE - if set to 1, enable sw fallbacks to improve
+ OpenGL conformance. If set to 2, always use software rendering.
+<li>INTEL_NO_BLIT - if set, disable hardware-accelerated glBitmap,
+ glCopyPixels, glDrawPixels.
+</ul>
+
+
+<h2>Radeon R300 driver environment variables (non-Gallium)</h2>
+
+<ul>
+<li>R300_NO_TCL - if set, disable hardware-accelerated Transform/Clip/Lighting.
+</ul>
+
+
+<h2>EGL environment variables</h2>
+
+<p>
+Mesa EGL supports different sets of environment variables. See the
+<a href="egl.html">Mesa EGL</a> page for the details.
+</p>
+
+
+<h2>Gallium environment variables</h2>
+
+<ul>
+<li>GALLIUM_PRINT_OPTIONS - if non-zero, print all the Gallium environment
+ variables which are used, and their current values.
+<li>GALLIUM_NOSSE - if non-zero, do not use SSE runtime code generation for
+ shader execution
+<li>GALLIUM_NOPPC - if non-zero, do not use PPC runtime code generation for
+ shader execution
+<li>GALLIUM_DUMP_CPU - if non-zero, print information about the CPU on start-up
+<li>TGSI_PRINT_SANITY - if set, do extra sanity checking on TGSI shaders and
+ print any errors to stderr.
+<LI>DRAW_FSE - ???
+<LI>DRAW_NO_FSE - ???
+<li>DRAW_USE_LLVM - if set to zero, the draw module will not use LLVM to execute
+ shaders, vertex fetch, etc.
+</ul>
+
+<h3>Softpipe driver environment variables</h3>
+<ul>
+<li>SOFTPIPE_DUMP_FS - if set, the softpipe driver will print fragment shaders
+ to stderr
+<li>SOFTPIPE_DUMP_GS - if set, the softpipe driver will print geometry shaders
+ to stderr
+<li>SOFTPIPE_NO_RAST - if set, rasterization is no-op'd. For profiling purposes.
+<li>SOFTPIPE_USE_LLVM - if set, the softpipe driver will try to use LLVM JIT for
+ vertex shading procesing.
+</ul>
+
+
+<h3>LLVMpipe driver environment variables</h3>
+<ul>
+<li>LP_NO_RAST - if set LLVMpipe will no-op rasterization
+<li>LP_DEBUG - a comma-separated list of debug options is acceptec. See the
+ source code for details.
+<li>LP_PERF - a comma-separated list of options to selectively no-op various
+ parts of the driver. See the source code for details.
+<li>LP_NUM_THREADS - an integer indicating how many threads to use for rendering.
+ Zero turns of threading completely. The default value is the number of CPU
+ cores present.
+</ul>
+
+
+<p>
+Other Gallium drivers have their own environment variables. These may change
+frequently so the source code should be consulted for details.
+</p>
+
+
+<br>
+<br>
+
+
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