Problem when move the QDockWidget to under the window's Taskbar

1. Create and show some QDockWidget. I used 2 existing example of Qt: "Dock Widget Example" and "Main window"

2. Float one of DockWidgets

3. Move floated DockWidget to under the window's taskbar completely. This mean the DockWidget will be hidden by the taskbar

4. Resize the mainwindow to see the abnormal behavior of application:

• Child widget do not resize follow the mainwindow's resizing.
• Missing status bar.