[Development] Fix for the Regression caused by the fix for QTBUG-16252 (QTBUG-68939)

[René J.V. Bertin]

Hi,

I have come up with a PoC fix for the rendering glitch regression that was introduced by the fix for QTBUG-16252.
In fact, it seems this fix forgot that the size(hint) for a dock area should be (0,0) when none of the widgets attached to that area are visible; failing to take that into account causes the dock area to be rendered as an empty space. To the user this looks as if the content view in the area surrounded by the docks doesn't size to take up all space available to it.

My PoC fix just scans over all widgets attached to each of the dock areas under consideration, until it finds one that is not skipped, visible and not floating. I looked for but couldn't find a QDockArea state variable that registers whether or not the area in question is collapsed or expanded - did I miss something?

Thanks,
R.