QSizeGrip doesn't update corner correctly when undocking from main window

QSizeGrip uses a heuristic to determine how to do the resizing depending on its location in the rectangle of its window. However, if the size grip is on a QDockWidget that is docked and then becomes undocked, the corner is not updated on undocking. That leads to funny effects that depend on where the dock was located in the main window. If the dock was somewhere in the lower right corner, it will work as expected. If it was docked on the left, the left edge of the floating dock window will now move even if the size grip is in the right-hand corner. 

Currently, the corner is set on initialization in QSizeGripPrivate::init and updated (using different logic!) if the QSizeGrip itself is moved. The corner needs to be re-evaluated more often, or perhaps one needs to be able to set it explicitly?

I managed to work around the issue by manually sending a QMoveEvent to the size grip at the moment of docking status change.