Endless Loop with QTreeView and QGraphicsView

When I embed a QTreeView in a QGraphicsView and call .setHeaderHidden(true) on the tree view then when the graphics view is shown, the CPU usage indefinitely spikes to 100% and Qt appears to be in an endless loop of painting.

Steps to reproduce:

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I used PySide2 in Python to reproduce the bug but I believe the same can be done in C++.

1) Download the attached test_tree_view.py.

2) Run "python test_tree_view.py" in a terminal to execute the script.

3) Hover the mouse over the opened PySide2/Qt window.

4) Python will now use 100% CPU for an indefinite period of time.

Other Notes:

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• Commenting out the `.setHeaderHidden(True)` line in the script avoids the bug.
• From my initial debugging it appeared to be an endless loop where QGraphicsView would paint, which caused the QTreeView to re-layout, which triggered the QGraphicsView to paint again, which caused the QTreeView to re-layout again, etc.
• The bug only occurs if QTreeView is embedded in a QGraphicsView.