Appendix R. The X Composite Extension version X11R6.8.0 contains experimental support for a new X protocol extension called Composite. This extension allows windows to be drawn into pixmaps instead of directly onto the screen. In conjunction with the DAMAGE and RENDER extensions, this allows a program called a composite manager to blend windows together to draw the screen.

Performance can be improved by enabling the RenderAccel option in xorg.conf. See Appendix D, X Config Options for more details.

Full Composite support will require additional driver support. Currently, direct rendering clients such as GLX have no way of knowing that they are supposed to render into a pixmap, and will draw directly to the screen instead. We are currently investigating what is necessary for such clients to interoperate seamlessly with Composite. In the meantime, GLX will be disabled by default when the Composite extension is detected. An option has been provided to re-enable it. See AllowGLXWithComposite in Appendix D, X Config Options.

This issue was discussed on the xorg mailing list:

Composite also causes problems with other driver components:

More information about Composite can be found at