With currently distributed versions of Mesa, calling XFreePixmap()
before glxDestroyPixmap() will cause an X error from DRI. So, we
need to make sure that we get rid of the CoglTexturePixmapX11 before
we XFreePixmap().
clutter_x11_texture_pixmap_dispose(): Call
clutter_x11_texture_pixmap_set_pixmap() instead of using XFreePixmap
directly so that we leverage the text-clearing hack and destroy
things in the right order.
clutter_x11_texture_pixmap_set_pixmap(): Don't do a pointless roundtrip
and trap a pointless error when setting pixmap to None.
clutter_x11_texture_pixmap_set_pixmap(): Free damage resources when
we are setting Pixmap to None.
clutter_x11_texture_pixmap_set_window(): When setting a new window
or setting the window to None, immedediately call
cluter_x11_texture_pixmap_set_pixmap(). This means that set_window(None)
immediately will free any referenced resources related to the window.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2303