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-<TITLE>Xlib Software Driver</TITLE>
+<div class="header">
+ <h1>The Mesa 3D Graphics Library</h1>
+</div>
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+<div class="content">
-<BODY>
-
-<H1>Xlib Software Driver</H1>
+<h1>Xlib Software Driver</h1>
<p>
Mesa's Xlib driver provides an emulation of the GLX interface so that
<p>
Since the Xlib driver <em>emulates</em> the GLX extension, it's not
-totally conformance with a true GLX implementation.
+totally conformant with a true GLX implementation.
The differences are fairly obscure, however.
</p>
</p>
-<H2>X Display Modes</H2>
+<h2>X Visual Selection</h2>
<p>
Mesa supports RGB(A) rendering into almost any X visual type and depth.
</p>
</pre>
-<H2>Double buffering</H2>
+<h2>Double Buffering</h2>
<p>
-Mesa can use either an X Pixmap or XImage as the backbuffer when in
-double buffer mode. Using GLX, the default is to use an XImage. The
-<b>MESA_BACK_BUFFER</b> environment variable can override this. The valid
-values for <b>MESA_BACK_BUFFER</b> are: <b>Pixmap</b> and <b>XImage</b>
-(only the first letter is checked, case doesn't matter).
+Mesa can use either an X Pixmap or XImage as the back color buffer when in
+double-buffer mode.
+The default is to use an XImage.
+The <b>MESA_BACK_BUFFER</b> environment variable can override this.
+The valid values for <b>MESA_BACK_BUFFER</b> are: <b>Pixmap</b> and
+<b>XImage</b> (only the first letter is checked, case doesn't matter).
</p>
<p>
-A pixmap is faster when drawing simple lines and polygons while an
-XImage is faster when Mesa has to do pixel-by-pixel rendering. If you
-need depth buffering the XImage will almost surely be faster.
+Using XImage is almost always faster than a Pixmap since it resides in
+the application's address space.
+When glXSwapBuffers() is called, XPutImage() or XShmPutImage() is used
+to transfer the XImage to the on-screen window.
+</p>
+<p>
+A Pixmap may be faster when doing remote rendering of a simple scene.
+Some OpenGL features will be very slow with a Pixmap (for example, blending
+will require a round-trip message for pixel readback.)
+</p>
+<p>
Experiment with the MESA_BACK_BUFFER variable to see which is faster
for your application.
</p>
-<H2>Colormaps</H2>
+<h2>Colormaps</h2>
<p>
When using Mesa directly or with GLX, it's up to the application
writer to create a window with an appropriate colormap. The GLUT
</p>
-<H2>Gamma correction</H2>
+<h2>Gamma Correction</h2>
<p>
To compensate for the nonlinear relationship between pixel values
and displayed intensities, there is a gamma correction feature in
% export MESA_GAMMA="2.0" // same gamma for R,G,B
</pre>
<p>
-The progs/demos/gamma.c program may help you to determine reasonable gamma
-value for your display. With correct gamma values, the color intensities
-displayed in the top row (drawn by dithering) should nearly match those
-in the bottom row (drawn as grays).
+The <code>demos/gamma.c</code> program in mesa/demos repository may help
+you to determine reasonable gamma value for your display. With correct
+gamma values, the color intensities displayed in the top row (drawn by
+dithering) should nearly match those in the bottom row (drawn as grays).
</p>
<p>
<p>
For more information about gamma correction see:
-<a href="http://www.inforamp.net/~poynton/notes/colour_and_gamma/GammaFAQ.html"
+<a href="http://www.inforamp.net/~poynton/notes/colour_and_gamma/GammaFAQ.html">
the Gamma FAQ</a>
</p>
-<H2>Overlay Planes</H2>
+<h2>Overlay Planes</h2>
<p>
Hardware overlay planes are supported by the Xlib driver. To
determine if your X server has overlay support you can test for the
</pre>
-<H2>HPCR glClear(GL_COLOR_BUFFER_BIT) dithering</H2>
+<h2>HPCR Dithering</h2>
<p>
If you set the <b>MESA_HPCR_CLEAR</b> environment variable then dithering
will be used when clearing the color buffer. This is only applicable
to HP systems with the HPCR (Color Recovery) feature.
+This incurs a small performance penalty.
</p>
-<H2>Extensions</H2>
+<h2>Extensions</h2>
<p>
The following MESA-specific extensions are implemented in the Xlib driver.
</p>
This extension was added in Mesa 2.0.
</p>
-<H3>GLX_MESA_copy_sub_buffer</H3>
+<h3>GLX_MESA_copy_sub_buffer</h3>
<p>
This extension adds the glXCopySubBufferMESA() function. It works
like glXSwapBuffers() but only copies a sub-region of the window
This extension was added in Mesa 2.6
</p>
-<h2>Summary of X-related environment variables</H2>
+<h2>Summary of X-related environment variables</h2>
<pre>
MESA_RGB_VISUAL - specifies the X visual and depth for RGB mode (X only)
MESA_CI_VISUAL - specifies the X visual and depth for CI mode (X only)
MESA_GAMMA - gamma correction coefficients (X only)
</pre>
-
+</div>
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</html>
projects / mesa.git / blobdiff