Details
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Bug
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Resolution: Won't Do
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P2: Important
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None
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4.6.2
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None
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MacOS/X 10.6.2 running on a Mac Pro (8 core, 2GB RAM)
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macOS
Description
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.
To reproduce:
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.
73.8% 73.8% QtGui qt_mac_drawCGImage(CGContext*, CGRect const*, CGImage*) 0.0% 73.7% QtGui qt_mac_draw_pattern(void*, CGContext*) 0.0% 73.7% QtGui QCoreGraphicsPaintEnginePrivate::drawPath(unsigned char, CGPath*) 0.0% 72.9% QtGui QCoreGraphicsPaintEngine::drawRects(QRectF const*, int) 0.0% 72.9% QtGui QPaintEngine::drawRects(QRect const*, int) 0.0% 72.9% QtGui QPainter::drawRects(QRect const*, int) 0.0% 72.0% QtGui QPainter::fillRect(QRect const&, QBrush const&) 0.0% 72.0% QtGui QWindowsStyle::drawPrimitive(QStyle::PrimitiveElement, QStyleOption const*, QPainter*, QWidget const*) const 0.0% 72.0% QtGui QTreeView::drawBranches(QPainter*, QRect const&, QModelIndex const&) const 0.0% 72.0% QtGui QTreeView::drawRow(QPainter*, QStyleOptionViewItem const&, QModelIndex const&) const 0.0% 72.0% QtGui QTreeView::drawTree(QPainter*, QRegion const&) const 0.0% 72.0% QtGui QTreeView::paintEvent(QPaintEvent*)