I've been working with panels a bunch lately, but there's quite a limited amount of functionality to them.

One such thing is sizing.

My usecase involves floating elements over the desktop. Where a panel, even if invisible and disabled, still occupies a space that denies the area of desktop, or perhaps even another panel beneath it.

For the use as a floating element, some elements will be shown or hidden on demand.

The one pixel panel trick works for cases where you want the panel present but out of the way, but falls apart for something that is toggled. For example, an expanding menu that creates controls, then destroys them. For this menu, the panel whom is allowed to expand, will grow to accommodate the size of its contents (windowclass + controls). However, if the windowinstance deletes all of its controls and shrinks to 1x1 pixel, the panel will keep the size and shape of the windowinstance when it was at its largest, with no way to access it.

You can use <dynamic/> but that requires user interaction as opposed to something you'd want automated, such as shrinking menus etc...