/* set the allocation for the whole button */
CLUTTER_ACTOR_CLASS (cb_button_parent_class)->allocate (actor, box, flags);
- /* make the child (the ClutterBox) fill the parent */
+ /* make the child (the ClutterBox) fill the parent;
+ * note that this allocation box is relative to the
+ * coordinates of the whole button actor, so we can't just
+ * use the box passed into this function; instead, it
+ * is adjusted to span the whole of the actor, from its
+ * top-left corner (0,0) to its bottom-right corner
+ * (width,height)
+ */
child_box.x1 = 0.0;
child_box.y1 = 0.0;
child_box.x2 = clutter_actor_box_get_width (box);