I am puting a QWidget and a QTabWidget next to each other in one horisontal splitter. And the splitter loses it\'s shape, you can know that there is a splitter only by hovering
Thanks to Merula's answer... I tried this and now my splitters are visible and look very nice without looking obtrusive. This code is for Python using PyQt or PySide.
app = QtGui.QApplication(sys.argv)
app.setStyle("Plastique") # set style (using this style shows splitters! :)