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QGraphicsView: Create high-dpi background pixmap

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Scale pixmap size by the viewport devicePixelRatio,
and make sure scrolling deltas and expose regions
are correctly scaled.

Change-Id: Ibeac34c5ecd531ca7c09802f0b5e1f45b8e31b65
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
This commit is contained in:
Morten Johan Sørvig 2016-11-23 15:16:09 +01:00
parent 8412009de6
commit 19950b3267
1 changed files with 11 additions and 3 deletions
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14
src/widgets/graphicsview/qgraphicsview.cpp
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@ -3483,7 +3483,9 @@ void QGraphicsView::paintEvent(QPaintEvent *event)
// Recreate the background pixmap, and flag the whole background as
// exposed.
if (d->mustResizeBackgroundPixmap) {
d->backgroundPixmap = QPixmap(viewport()->size());
const qreal dpr = d->viewport->devicePixelRatioF();
d->backgroundPixmap = QPixmap(viewport()->size() * dpr);
d->backgroundPixmap.setDevicePixelRatio(dpr);
QBrush bgBrush = viewport()->palette().brush(viewport()->backgroundRole());
if (!bgBrush.isOpaque())
d->backgroundPixmap.fill(Qt::transparent);
@ -3679,14 +3681,20 @@ void QGraphicsView::scrollContentsBy(int dx, int dy)
&& X11->use_xrender
#endif
) {
// Below, QPixmap::scroll() works in device pixels, while the delta values
// and backgroundPixmapExposed are in device independent pixels.
const qreal dpr = d->backgroundPixmap.devicePixelRatio();
const qreal inverseDpr = qreal(1) / dpr;
// Scroll the background pixmap
QRegion exposed;
if (!d->backgroundPixmap.isNull())
d->backgroundPixmap.scroll(dx, dy, d->backgroundPixmap.rect(), &exposed);
d->backgroundPixmap.scroll(dx * dpr, dy * dpr, d->backgroundPixmap.rect(), &exposed);
// Invalidate the background pixmap
d->backgroundPixmapExposed.translate(dx, dy);
d->backgroundPixmapExposed += exposed;
const QRegion exposedScaled = QTransform::fromScale(inverseDpr, inverseDpr).map(exposed);
d->backgroundPixmapExposed += exposedScaled;
}
// Always replay on scroll.