Zoom Line Example▲
The example shows how to create your own custom zooming effect with QRubberBand by using a mouse and how to use touch gestures for paning and zooming.
Running the Example▲
To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.
Customizing Zooming Effects▲
Let's first create a line series with some example data.
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auto series = new QLineSeries;
for (int i = 0; i < 500; i++) {
QPointF p((qreal) i, qSin(M_PI / 50 * i) * 100);
p.ry() += QRandomGenerator::global()->bounded(20);
*series << p;
}Then we create a custom chart view by deriving from QChartView:
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class ChartView : public QChartViewWe override mouse and key event handling
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protected:
bool viewportEvent(QEvent *event);
void mousePressEvent(QMouseEvent *event);
void mouseMoveEvent(QMouseEvent *event);
void mouseReleaseEvent(QMouseEvent *event);
void keyPressEvent(QKeyEvent *event);Then we implement a custom logic for mouse and key events. For example pressing the '+' key will zoom in and pressing the '-' key will zoom out.
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void ChartView::keyPressEvent(QKeyEvent *event)
{
switch (event->key()) {
case Qt::Key_Plus:
chart()->zoomIn();
break;
case Qt::Key_Minus:
chart()->zoomOut();
break;We also create our own QChart:
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class Chart : public QChartWhere we can handle the gestures:
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bool Chart::sceneEvent(QEvent *event)
{
if (event->type() == QEvent::Gesture)
return gestureEvent(static_cast<QGestureEvent *>(event));
return QChart::event(event);
}
bool Chart::gestureEvent(QGestureEvent *event)
{
if (QGesture *gesture = event->gesture(Qt::PanGesture)) {
auto pan = static_cast<QPanGesture *>(gesture);
QChart::scroll(-(pan->delta().x()), pan->delta().y());
}
if (QGesture *gesture = event->gesture(Qt::PinchGesture)) {
auto pinch = static_cast<QPinchGesture *>(gesture);
if (pinch->changeFlags() & QPinchGesture::ScaleFactorChanged)
QChart::zoom(pinch->scaleFactor());
}
return true;
}Note that you will need to call grabGesture() to both QMainWindow and QChart.