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Make scroll wheel zoom less jumpy on fractional-scroll devices like touchpads

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Kevin Mehall
2017-02-04 10:21:26 -08:00
parent 705600ef50
commit 90d798a93b
2 changed files with 19 additions and 9 deletions
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27
plotview.cpp
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@@ -170,15 +170,24 @@ bool PlotView::viewportEvent(QEvent *event) {
if (event->type() == QEvent::Wheel) {
QWheelEvent *wheelEvent = (QWheelEvent*)event;
if (QApplication::keyboardModifiers() & Qt::ControlModifier) {
// `updateViewRange()` keeps the center sample in the same place after zoom. Apply
// a scroll adjustment to keep the sample under the mouse cursor in the same place instead.
int fromCenter = wheelEvent->pos().x() - width()/2;
if (wheelEvent->angleDelta().y() > 0 && zoomLevel < fftSize) {
emit zoomIn();
horizontalScrollBar()->setValue(horizontalScrollBar()->value() + fromCenter * samplesPerLine());
} else if (wheelEvent->angleDelta().y() < 0 && zoomLevel > 1) {
horizontalScrollBar()->setValue(horizontalScrollBar()->value() - fromCenter * samplesPerLine());
emit zoomOut();
bool canZoomIn = zoomLevel < fftSize;
bool canZoomOut = zoomLevel > 1;
int delta = wheelEvent->angleDelta().y();
if ((delta > 0 && canZoomIn) || (delta < 0 && canZoomOut)) {
scrollZoomStepsAccumulated += delta;
// `updateViewRange()` keeps the center sample in the same place after zoom. Apply
// a scroll adjustment to keep the sample under the mouse cursor in the same place instead.
int fromCenter = wheelEvent->pos().x() - width()/2;
if (scrollZoomStepsAccumulated >= 120) {
scrollZoomStepsAccumulated -= 120;
emit zoomIn();
horizontalScrollBar()->setValue(horizontalScrollBar()->value() + fromCenter * samplesPerLine());
} else if (scrollZoomStepsAccumulated <= -120) {
scrollZoomStepsAccumulated += 120;
horizontalScrollBar()->setValue(horizontalScrollBar()->value() - fromCenter * samplesPerLine());
emit zoomOut();
}
}
return true;
}