How to add toggle fullscreen button into QDockWidget in PyQt4?

Question

By default, there are two small buttons on the QDockWidget toolbar: "detach" and "close".

How can I add a new button: "toggle fullscreen"?

Answer 1

The QDockWidget.setTitleBarWidget function can be used to replace the existing titlebar (including buttons) with a custom widget of your own.

However, it's not possible to use QDockWidget.titleBarWidget get a reference to the default titlebar widget and add extra buttons to it.