Minimized windows shown as small rectangles
Qt 4.8 and 5.4, Qt Creator 3.1 and 3.3.0 under Ubuntu 12.04
Since installation of Qt 5.4 and Qt Creator 3.3.0 my Qt apps show a defect.
If I minimize a subwindow, its corresponding "tab" that was previously at the bottom left of the main window now shows as a tiny rectangle.
Even if I rebuild with Qt Creator 3.1.2 using Qt 4.8 the defect remains.
I cannot imagine what happened since I did not modified the code since the Qt/Qt Creator upgrade, only recompile the app.
The small rectangle stays active and the window menu can still be used by hovering the mouse curson on it.
Any advice would be very welcome!