Hover and Highlight QTable and QTree Items

[jpn]

Have you enabled mouse tracking on the viewport and also installed the event filter on the viewport?

treeWidget->viewport()->setMouseTracking(true);
treeWidget->viewport()->installEventFilter(this);

treeWidget->viewport()->setMouseTracking(true);
treeWidget->viewport()->installEventFilter(this);

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Edit: is the tree massive, containing huge amount of items in a complex hierarchy?