QMainWindow: When there is no central widget then it is not always possible to resize a dock widget. In the example attached you can resize vertically but once you try to resize again it will not allow it to get smaller, it will only get bigger.

Steps to reproduce:

• Enlarge bottom dock labeled "console" vertically by dragging its top border up
• Try to do the reverse: Dock cannot be shrunk. Works with central widget ("-c")