Undocked panels/docks hard to re-dock on macOS

[Boris Dalstein]

More generally, VPaint docks are incredibly frustrating to use on macOS (tried on macOS 10.11). Sometimes, trying to simply resize them cause them to be undocked, and then trying to redock them is either really hard or impossible. Undocking+redocking another dock sometimes helps.

I reported this here: https://bugreports.qt.io/browse/QTBUG-69922

Since this creates so much frustration, I'm considering disabling the ability to create floating docks. In VGC, I'll probably implement my own panel system, more similar to how Blender / Qt Creator does it, since QDockWidget seems often broken (see Qt bug history), inconsistent across platforms, and doesn't have nice features we might meed (e.g., "+" icon next to tabs to add new Panel, and better management of PanelArea layout). And quite frankly, the fact that Qt Creator don't use them means that the Qt team is quite likely not to polish them in the future (they are not personally affected by QDockWidget bugs), and that even expert Qt developers prefer not to use them.

Related:
https://bugreports.qt.io/browse/QTBUG-46882
https://codereview.qt-project.org/#/c/232845/
https://bugreports.qt.io/browse/QTBUG-53819?attachmentViewMode=list
https://forum.qt.io/topic/680/qdockwidget-will-not-go-from-floating-back-to-the-docked-state-why