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| -rw-r--r-- | docs/xlibdriver.html | 25 |
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> |