glXCreateGLXPixmap creates an off-screen rendering area and returns its XID. Any GLX rendering context that was created with respect to vis can be used to render into this off-screen area. Use glXMakeCurrent to associate the rendering area with a GLX rendering context.The X pixmap identified by pixmap is used as the front left buffer of the resulting off-screen rendering area. All other buffers specified by vis, including color buffers other than the front left buffer, are created without externally visible names. GLX pixmaps with double-buffering are supported. However, glXSwapBuffers is ignored by these pixmaps.
Some implementations may not support GLX pixmaps with direct rendering contexts.