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| author | Shawn Rutledge <shawn.rutledge@qt.io> | 2017-09-14 15:14:32 +0200 |
|---|---|---|
| committer | Shawn Rutledge <shawn.rutledge@qt.io> | 2018-08-30 04:12:01 +0000 |
| commit | d2c05b0c8557625ce45cdbd98ebf102972d2c2f4 (patch) | |
| tree | 4cf778f249df164b35dd1ea3d5b482506244de73 /examples/widgets/widgets | |
| parent | 09f59271e677259e1e2ffd3b42fff107001f89a5 (diff) | |
Tablet example: paint only the changed areas of the canvas
This improves performance significantly.
Change-Id: I9a8782148ce03a2bc85759c4e8c1eecb37467cf6
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Diffstat (limited to 'examples/widgets/widgets')
| -rw-r--r-- | examples/widgets/widgets/tablet/tabletcanvas.cpp | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/examples/widgets/widgets/tablet/tabletcanvas.cpp b/examples/widgets/widgets/tablet/tabletcanvas.cpp index 3ff26d2ec8..bfcc84e182 100644 --- a/examples/widgets/widgets/tablet/tabletcanvas.cpp +++ b/examples/widgets/widgets/tablet/tabletcanvas.cpp @@ -148,12 +148,14 @@ void TabletCanvas::initPixmap() m_pixmap = newPixmap; } -void TabletCanvas::paintEvent(QPaintEvent *) +void TabletCanvas::paintEvent(QPaintEvent *event) { if (m_pixmap.isNull()) initPixmap(); QPainter painter(this); - painter.drawPixmap(0, 0, m_pixmap); + QRect pixmapPortion = QRect(event->rect().topLeft() * devicePixelRatioF(), + event->rect().size() * devicePixelRatioF()); + painter.drawPixmap(event->rect().topLeft(), m_pixmap, pixmapPortion); } //! [4] |