[Regression] QTabWidget documentMode not working correctly on Mac

On Mac, QTabWidget with setDocumentMode(true) should be visually "unified" with the titlebar.

Indeed, that is the very intention of the call to setDocumentMode. See this Qt Labs blog post (particularly the screenshot): http://labs.trolltech.com/blogs/2008/07/02/some-qtabbar-qtabwidget-love/

Unfortunately, the tabs and window titlebar do not get "unified". I've tried the latest 4.5 and 4.6 versions, using both Carbon and Cocoa. Here is what it actually looks like: http://boxybutgood.com/~jeff/QTabWidget.png

The problem happens both when you programatically set a QTabWidget as the QMainWindow's central widget and also when using Qt Designer. Interesting to note: when using Qt Designer, the PREVIEW mode displays the desired behavior! But when you actually use the class in your application, you get the non-unified appearance.

Also, fwiw, setUnifiedTitleAndToolBarOnMac(true) has no effect on this.