
cairo_region_copy, while valid to call on a NULL pointer, gives us an empty region instead of an infinitely big region, so the interesction won't give us what we want. Just check for this case explicitly. https://bugzilla.gnome.org/show_bug.cgi?id=707081
Intro ===== Fix me. Env Vars ======== MUTTER_DISABLE_MIPMAPS - set to disable use of mipmaped windows.