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HighDPI: Disable scrolling for non-integer deltas 

Disable the scrolling optimization in QBackingStore
and fall back to repainting for non-integer deltas.
The existing rendered pixels are not re-usable in
this case.

The test is made on the delta, and not on the scale
factor. This means that user code can cooperate and
generate (logical delta, scale factor) combinations
that result in integer pixel deltas (which _can_ be
scrolled).

Change-Id: I36eb5d9e00449428bc9095edd8732782b996db16
Task-number: QTBUG-52452
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
bb10
Morten Johan Sørvig 2016-07-26 13:16:53 +02:00
parent 97318a3d5f
commit a2157df28b
1 changed files with 9 additions and 4 deletions
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13
src/gui/painting/qbackingstore.cpp
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@ -230,11 +230,16 @@ QSize QBackingStore::size() const
*/
bool QBackingStore::scroll(const QRegion &area, int dx, int dy)
{
Q_UNUSED(area);
Q_UNUSED(dx);
Q_UNUSED(dy);
// Disable scrolling for non-integer scroll deltas. For this case
// the the existing rendered pixels can't be re-used, and we return
// false to signal that a repaint is needed.
const qreal nativeDx = QHighDpi::toNativePixels(qreal(dx), d_ptr->window);
const qreal nativeDy = QHighDpi::toNativePixels(qreal(dy), d_ptr->window);
if (qFloor(nativeDx) != nativeDx || qFloor(nativeDy) != nativeDy)
return false;
return d_ptr->platformBackingStore->scroll(QHighDpi::toNativeLocalRegion(area, d_ptr->window), QHighDpi::toNativePixels(dx, d_ptr->window), QHighDpi::toNativePixels(dy, d_ptr->window));
return d_ptr->platformBackingStore->scroll(QHighDpi::toNativeLocalRegion(area, d_ptr->window),
nativeDx, nativeDy);
}
/*!