Priority: P2: Important
Affects Version/s: 4.6.2
Fix Version/s: None
Component/s: GUI: Look'n'Feel
MacOS/X 10.6.2 running on a Mac Pro (8 core, 2GB RAM)
When use the QTreeView class on a Mac, with the app's style set to QWindowsStyle, the GUI is really slow/laggy/jerky as I resize the window, resize column headers, scroll the view, etc. Doing any of those things also causes one core of my Mac's CPU to shoot up to 90+%. If the QWindowsStyle is not applied, however, then the GUI is quite responsive and CPU load stays negligible.
1) Add the following lines to $QTDIR/examples/itemviews/simpletreemodel/main.cpp:
app.setStyle(new QWindowsStyle); // add this just after the QApplication object is declared
view.expandAll(); // add this just before view.show()
2) Compile and run the application, and see what the app's GUI performance is like (as described above)
3) Command out the app.setStyle() command (above) and then recompile and test the GUI performance is like again. It should be a LOT faster/smoother now.
Relevant part of the shark report - looks like the windows style hits a particularly slow path in the Core Graphics paint engine.