Rendering sub tools on vertical toolbar

Question

I was wondering how ex Photoshop and Expression Design render sub tools. These show up when for example you hold your mouse down on the fill tool, a sub menu comes up to your right with the fill and gradient tools. I'm just not sure how to go about this because this sub menu would essentially have to be an extension of my toolbar, but then it would find itself on my Frame control. How is this handled? Would it be a good idea to just paint on my frame? Thanks

Answer 1

I'm pretty sure that they are created as bona fide transient windows much as the pop-up File menu and sub-menus are. I'd look at the source of GTK or similar to see how precisely that is done.

Painting directly on the frame tends to make a window system unhappy.