How to "flush" display?

[Caius Aérobus]

Hello,
I have a class inherited from QAbstractItemView in which the mouseReleaseEvent() method have been overloaded so as to perform selection of items. The selection works well and the paintEvent() method is supposed to highlight them. It works well, ie the right items are selected, but I need to cover part of the widget and them show it again for paintEvent() to be executed. I tried almost everything I could think about as a solution, which leads now:

this->update();
QCoreApplication::processEvents();
QCoreApplication::flush();

this->update();
QCoreApplication::processEvents();
QCoreApplication::flush();

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but paintEvent() is still not synchronously called.
So how to cope with this issue?