Xwidget is really buggy.
I expect a transparent area not to register a click. It should only register a click event when an opaque section is clicked upon. Xwidget has a serious bug that causes transparent areas to accept clicks.
This is particularly pronounced on circular rotator or image objects as they have a large area of transparency around them at the boundaries. Circular images are not really circular at all. They are square images with circular area upon them but with the rest of the area filled with a transparent mask. This area is clickable and it SHOULD NOT BE.
This bug means that you cannot have circular areas in your widget that have clickable items underneath them. If these underlying objects have click events assigned to them then the click event is never called as you cannot click on these underlying images. The image above extends over them. The only way for the underlying images to take a click is for the upper layer to allow mousethrough. This is not a useful property as it stops the top layer from being clickable.

This relates to a previous forum post where the accidental acceptance of a click on a transparent area was recognised as a BUG - nothing was done about so Xwidget to this day contains this SERIOUS FLAW. It makes Xwidget unusable for many widget types. At least twice now I have set about converting a widget to Xwidget only to find that Xwidget's buggy implementation prevents a normal, usable widget from being created.
http://bbs.xwidget.com/viewtopic.php?f=3&t=3427Xwidget in its current state is buggy and unusable for serious work. It is OK for kiddy stuff but these BASIC bugs need to be fixed before anyone will ever take this product seriously.

This is the Xwidget that I was converting and once again I gave up due to this horrendous bug! Note that all the components sit closely together beneath a circular clockface. That clockface obscures all the underlying objects from being clickable.