Design mechanism for widgets that may need to "pop up"

[Updownquark]

Right now widgets are given a set of bounds and can only paint and receive events within that boundary. But some widgets, e.g. tool tips, menus, and combo boxes, pop up a widget that needs to be able to render and receive events outside of those bounds somehow.

Some problems:

• The pop up should not be layed out by a layout manager, but should have its bounds manipulated directly by the owning widget. (So can't just add it to the parent).
• The pop up should be displayed on top of and receive mouse events before the owning widget's ancestors, but should be painted under and have its events blocked by siblings or uncles, etc. that have higher Z-index than the sibling that is the ancestor of the owning widget. (So no global glass pane)

[Updownquark]

Added the "paint bounds" concept. The MuisElement.getPaintBounds() method returns a rectangle in element coordinates that describes where the element may draw. This rectangle is used to update the cached bounds as well (though this rectangle is in parent coordinates), which is used by the positional event (e.g. mouse) code; so widgets will also receive events that occur inside their paint bounds. This should enable all the functionality and meet all the requirements outlined in the OP.