Qt Documentation

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PinchHandler QML Type

Handler for pinch gestures. More...

Import Statement: import QtQuick 2.12
Inherits:

MultiPointHandler

Properties

Detailed Description

PinchHandler is a handler that interprets a multi-finger gesture to interactively rotate, zoom, and drag an Item. Like other Input Handlers, by default it is fully functional, and manipulates its target, which is the Item within which it is declared.

import QtQuick 2.12

Rectangle {
    width: 400
    height: 300
    color: "lightsteelblue"
    PinchHandler { }
}

It has properties to restrict the range of dragging, rotation, and zoom.

If it is declared within one Item but is assigned a different target, it handles events within the bounds of the outer Item but manipulates the target Item instead:

import QtQuick 2.12

Item {
    width: 640
    height: 480

    Rectangle {
        id: map
        color: "aqua"
        width: 400
        height: 300
    }

    PinchHandler {
        target: map
    }
}

A third way to use it is to set target to null and react to property changes in some other way:

import QtQuick 2.12

Item {
    width: 640
    height: 480

    PinchHandler {
        id: handler
        target: null
    }

    Text {
        color: handler.active ? "darkgreen" : "black"
        text: handler.rotation.toFixed(1) + " degrees\n" +
              handler.translation.x.toFixed(1) + ", " + handler.translation.y.toFixed(1) + "\n" +
              (handler.scale * 100).toFixed(1) + "%"
    }
}

Note: The pinch begins when the number of fingers pressed is between minimumPointCount and maximumPointCount, inclusive. Until then, PinchHandler tracks the positions of any pressed fingers, but if it's a disallowed number, it does not scale or rotate its target, and the active property remains false.

See also PinchArea and QPointerEvent::pointCount().

Property Documentation

active : bool

This property is true when all the constraints (epecially minimumPointCount and maximumPointCount) are satisfied and the target, if any, is being manipulated.


[read-only] activeScale : real

The scale factor while the pinch gesture is being performed. It is 1.0 when the gesture begins, increases as the touchpoints are spread apart, and decreases as the touchpoints are brought together. If target is not null, its scale will be automatically multiplied by this value. Otherwise, bindings can be used to do arbitrary things with this value.


[read-only] centroid : QtQuick::HandlerPoint

A point exactly in the middle of the currently-pressed touch points. The target will be rotated around this point.


maximumRotation : real

The maximum acceptable rotation to be applied to the target.


maximumScale : real

The maximum acceptable scale to be applied to the target.


minimumRotation : real

The minimum acceptable rotation to be applied to the target.


minimumScale : real

The minimum acceptable scale to be applied to the target.


[read-only] rotation : real

The rotation of the pinch gesture in degrees, with positive values clockwise. It is 0 when the gesture begins. If target is not null, this will be automatically applied to its rotation. Otherwise, bindings can be used to do arbitrary things with this value.


[read-only] scale : real

The scale factor that will automatically be set on the target if it is not null. Otherwise, bindings can be used to do arbitrary things with this value. While the pinch gesture is being performed, it is continuously multiplied by activeScale; after the gesture ends, it stays the same; and when the next pinch gesture begins, it begins to be multiplied by activeScale again.


[read-only] translation : QVector2D

The translation of the gesture centroid. It is (0, 0) when the gesture begins.


xAxis group

xAxis.minimum : real

xAxis.maximum : real

xAxis.enabled : bool

xAxis controls the constraints for horizontal translation of the target item.

minimum is the minimum acceptable x coordinate of the translation. maximum is the maximum acceptable x coordinate of the translation. If enabled is true, horizontal dragging is allowed.


yAxis group

yAxis.minimum : real

yAxis.maximum : real

yAxis.enabled : bool

yAxis controls the constraints for vertical translation of the target item.

minimum is the minimum acceptable y coordinate of the translation. maximum is the maximum acceptable y coordinate of the translation. If enabled is true, vertical dragging is allowed.


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