An opaque type that tracks a #CoglOnscreenDirtyCallback and associated
user data. A #CoglOnscreenDirtyClosure pointer will be returned from
cogl_onscreen_add_dirty_callback() and it allows you to remove a
callback later using cogl_onscreen_remove_dirty_callback().
An opaque type that tracks a #CoglOnscreenDirtyCallback and associated user data. A #CoglOnscreenDirtyClosure pointer will be returned from cogl_onscreen_add_dirty_callback() and it allows you to remove a callback later using cogl_onscreen_remove_dirty_callback().