Flickering toolbars

Floating toolbars flicker when undoing/redoing view changes.


They flicker also when opening a scene, meaning they ‘jump’ up/down a pixel.
There seem to be useless UI refresh messages. But even so, how come that their positions changes slightly?

Ideally, there panel/toolbar mechanics would be updated on windows, a dark theme introduced, a good way to save/load/share a custom UI layout added.
An old topic. Lots of old code in there I assume. Hopefully not too much to be realistically fixable.