Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Zoom Line Example

The example shows how to create your own custom zooming effect.

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.

series = QLineSeries()
for i in range(0, 500):
    p = QPointF((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 :

class ChartView(QChartView):

We override mouse and key event handling

# protected
    viewportEvent = bool(QEvent event)
    def mousePressEvent(event):
    def mouseMoveEvent(event):
    def mouseReleaseEvent(event):
    def keyPressEvent(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.

def keyPressEvent(self, event):

    switch (event.key()) {
    elif socketError == Qt.Key_Plus:
        chart().zoomIn()
        break
    elif socketError == Qt.Key_Minus:
        chart().zoomOut()
        break

We also create our own QChart :

class Chart(QChart):

Where we can handle the gestures:

def sceneEvent(self, QEvent event):

    if event.type() == QEvent.Gesture:
        return gestureEvent(QGestureEvent(event))
    return QChart.event(event)

def gestureEvent(self, QGestureEvent event):

    if QGesture gesture = event.gesture(Qt.PanGesture):
        pan = QPanGesture(gesture)
        QChart.scroll(-(pan.delta().x()), pan.delta().y())

    if QGesture gesture = event.gesture(Qt.PinchGesture):
        pinch = 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 .

Example project @ code.qt.io