QStyledItemDelegate draws overlapping items in QComboBox

The sizeHint method of the item delegate of a QComboBox is called with very different option.rect values depending on option.state. Thus it is impossible to compute an appropriate sizeHint using option.rect.width(), and when paint is later called, drop-down items are drawn overlapping.

For example, sizeHint is called first with an option.rect with width 624, then 0, then 27, then 640, then 0, then 27, then finally 50.
paint is only called with an option.rect with a (correct) width of 50.

I've attached an example that illustrates the problem as well as an image with the incorrectly drawn combo drop-down.

cheers,
-Mark