When using native dock widgets on macOS, it will currently
fail if you try to drag on a dock widget inside QMainWindow
to make it floating. The reason is that the drag will
basically start as as drag inside one NSWindow (QMainWindow),
but continue as a drag on another NSWindow (QDockWidget).
And this is not handled well by AppKit, especially since the
NSView where the drag was started is reparented into a new
NSWindow (the floating QDockWidget) while the dragging is
ongoing. And there seems to be no practical solution to how
we can support this from the cocoa QPA plugin
This patch will therefore change the logic in QDockWidget to
simply make the dock widget floating if you drag on it, rather
than actually starting a drag (but only for the described case).
Pick-to: 6.1 5.15
Fixes: QTBUG-70137
Change-Id: Ic309ee8f419b9c14894255205867bce11dc0c414
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
3224c6d7d1