-<HTML>
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
+<html lang="en">
+<head>
+ <meta http-equiv="content-type" content="text/html; charset=utf-8">
+ <title>Xlib Software Driver</title>
+ <link rel="stylesheet" type="text/css" href="mesa.css">
+</head>
+<body>
-<TITLE>Xlib Software Driver</TITLE>
+<div class="header">
+ <h1>The Mesa 3D Graphics Library</h1>
+</div>
-<link rel="stylesheet" type="text/css" href="mesa.css"></head>
+<iframe src="contents.html"></iframe>
+<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
-toolkit tris to minimize colormap <em>flashing</em> by sharing
+toolkit tries to minimize colormap <em>flashing</em> by sharing
colormaps when possible. Specifically, if the visual and depth of the
window matches that of the root window, the root window's colormap
will be shared by the Mesa window. Otherwise, a new, private colormap
</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>
<p>
-For more information about gamma correction see:
-<a href="http://www.inforamp.net/~poynton/notes/colour_and_gamma/GammaFAQ.html"
-the Gamma FAQ</a>
+For more information about gamma correction, see the
+<a href="https://en.wikipedia.org/wiki/Gamma_correction">Wikipedia article</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.
+The following Mesa-specific extensions are implemented in the Xlib driver.
</p>
<h3>GLX_MESA_pixmap_colormap</h3>
extension.
</p>
<p>
-<a href="MESA_pixmap_colormap.spec">GLX_MESA_pixmap_colormap specification</a>
+<a href="specs/MESA_pixmap_colormap.spec">GLX_MESA_pixmap_colormap specification</a>
</p>
XDestroyWindow( dpy, window );
</pre>
<p>
-<a href="MESA_release_buffers.spec">GLX_MESA_release_buffers specification</a>
+<a href="specs/MESA_release_buffers.spec">GLX_MESA_release_buffers specification</a>
</p>
<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
instead of the whole window.
</p>
<p>
-<a href="MESA_copy_sub_buffer.spec">GLX_MESA_copy_sub_buffer specification</a>
+<a href="specs/MESA_copy_sub_buffer.spec">GLX_MESA_copy_sub_buffer specification</a>
</p>
<p>
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>
</body>
</html>
projects / mesa.git / blobdiff