How to display marquee animation of QProgressBar properly when using it in QTreeView

[wysota]

Is it possible to tell the QItemDelegate to call paint() more frequent?

You can connect a timer's timeout() signal to the view's update slot() (possibly passing in the coordinates of the item containing the progress bar). But don't be suprised if CPU usage will go sky high.

Is it possible to display an QProgressBar directly, instead of calling QApplication::style()->drawControl(...)?

Yes but you will have to control its geometry yourself (including clipping and showing/hiding the widget). An alternative is to use setIndexWidget() but then the bar will not be tied to your model in any way.