The fix for
QTBUG-16252 introduced a regression which I have so far only seen in KDevelop.
There, document views behave as if hidden dock widgets are in fact expanded, with the result that they are too narrow and not high enough. Expanding a dock widget (on any edge) and changing its width or height (or changing the width/height of an already expanded dock widget) restores the proper doc view dimensions. This fix persists when the dock widget is hidden again (= the doc view takes up all available space) but not when I change to another doc view (in KDevelop's tabbed interface).
Resizing the entire window doesn't help; doc views and the unoccupied space are resized proportionally.
This issue disappears when I revert commit #cbfb6bda1d1ce3e169db6a0deb9bd901076653e4 .