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authorBrian Paul <brian.paul@tungstengraphics.com>2006-06-07 14:01:31 +0000
committerBrian Paul <brian.paul@tungstengraphics.com>2006-06-07 14:01:31 +0000
commit808809b061e2ffa57b7d09cedbd57a190855100c (patch)
treecd666f673dc97ff3311060b7e0f8d47e6597993c
parent37474eca68ce5be9ac3746f700bc220b0f4c5420 (diff)
updated Pixmap vs. XImage info
-rw-r--r--docs/xlibdriver.html25
1 files changed, 17 insertions, 8 deletions
diff --git a/docs/xlibdriver.html b/docs/xlibdriver.html
index 6bb6532533..d95f4d579c 100644
--- a/docs/xlibdriver.html
+++ b/docs/xlibdriver.html
@@ -70,17 +70,26 @@ Here are some examples:
<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>