PinchHandler QML Type
Handler for pinch gestures. More...
Properties
- acceptedButtons : flags
- active : bool
- activeRotation : real
- activeScale : real
- activeTranslation : QPointF
- centroid : QtQuick::handlerPoint
- maximumRotation : real
- maximumScale : real
- minimumRotation : real
- minimumScale : real
- persistentRotation : real
- persistentScale : real
- persistentTranslation : QPointF
- rotation : QVector2D
- rotationAxis
- rotationAxis.activeValue : real
- rotationAxis.enabled : bool
- rotationAxis.maximum : real
- rotationAxis.minimum : real
- scale : QVector2D
- scaleAxis
- scaleAxis.activeValue : real
- scaleAxis.enabled : bool
- scaleAxis.maximum : real
- scaleAxis.minimum : real
- translation : QVector2D
- xAxis
- xAxis.activeValue : real
- xAxis.enabled : bool
- xAxis.maximum : real
- xAxis.minimum : real
- yAxis
- yAxis.activeValue : real
- yAxis.enabled : bool
- yAxis.maximum : real
- yAxis.minimum : real
Signals
- rotationChanged(qreal delta)
- scaleChanged(qreal delta)
- translationChanged(QVector2D delta)
Detailed Description
\inherits
MultiPointHandler \inqmlmodule
QtQuick \ingroup
qtquick-input-handlers
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.
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 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 Window { width: 320; height: 240 visible: true title: handler.persistentRotation.toFixed(1) + "° " + handler.persistentTranslation.x.toFixed(1) + ", " + handler.persistentTranslation.y.toFixed(1) + " " + (handler.persistentScale * 100).toFixed(1) + "%" PinchHandler { id: handler target: null persistentScale: 0.25 onTranslationChanged: (delta) => { image.x -= delta.x image.y -= delta.y } } Image { id: image source: "images/album-cover.jpg" scale: handler.persistentScale x: -600; y: -450 } }
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, QPointerEvent::pointCount(), QNativeGestureEvent::fingerCount(), and Qt Quick Examples - Pointer Handlers.
Property Documentation
acceptedButtons : flags |
\internal
This property is not used in PinchHandler.
[read-only] active : bool |
\readonly
This property is true
when all the constraints (epecially minimumPointCount and maximumPointCount) are satisfied and the target, if any, is being manipulated.
[read-only] activeRotation : real |
\readonly
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 added to its rotation. Otherwise, bindings can be used to do arbitrary things with this value.
See also QtQuick::PinchHandler::rotationAxis.activeValue.
[read-only] activeScale : real |
\readonly
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.
See also QtQuick::PinchHandler::scaleAxis.activeValue.
[read-only] activeTranslation : QPointF |
\readonly
The translation of the cluster of points while the pinch gesture is being performed. It is 0, 0
when the gesture begins, and increases as the eventPoint(s) are dragged downward and to the right. After the gesture ends, it stays the same; and when the next pinch gesture begins, it is reset to 0, 0
again.
Note: On some touchpads, such as on a macOS trackpad, native gestures do not generate any translation values, and this property stays at (0, 0)
.
[read-only] centroid : QtQuick::handlerPoint |
\readonly
A point exactly in the middle of the currently-pressed touch points. The target will be rotated around this point.
maximumRotation : real |
\deprecated
[6.5] Use rotationAxis.maximum
The maximum acceptable rotation to be applied to the target.
maximumScale : real |
minimumRotation : real |
\deprecated
[6.5] Use rotationAxis.minimum
The minimum acceptable rotation to be applied to the target.
minimumScale : real |
persistentRotation : real |
The rotation to be applied to 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, activeRotation is continuously added; after the gesture ends, it stays the same; and when the next pinch gesture begins, it begins to be modified by activeRotation again.
It's possible to set this property, as a way of synchronizing the basis rotation with a rotation that was set in some other way, for example by another handler. If you set this property directly, activeRotation
does not change, and rotationChanged(0)
is emitted.
persistentScale : 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.
It's possible to set this property, as a way of synchronizing the basis scale with a scale that was set in some other way, for example by another handler. If you set this property directly, activeScale
does not change, and scaleChanged(1)
is emitted.
persistentTranslation : QPointF |
The translation to be applied to 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, activeTranslation is continuously added to it; after the gesture ends, it stays the same.
It's possible to set this property, as a way of synchronizing the basis translation with a translation that was set in some other way, for example by another handler. If you set this property directly, activeTranslation
does not change, and translationChanged({0, 0})
is emitted.
Note: On some touchpads, such as on a macOS trackpad, native gestures do not generate any translation values, and this property stays at (0, 0)
.
[read-only] rotation : QVector2D |
\readonly
\deprecated
[6.5] Use activeRotation
rotationAxis
controls the constraints for setting the rotation of the target item according to the rotation of the group of touchpoints.
minimum
is the minimum acceptable rotation. maximum
is the maximum acceptable rotation. If enabled
is true, rotation is allowed. activeValue
is the same as QtQuick::PinchHandler::activeRotation.
The activeValueChanged
signal is emitted when activeValue
changes, to provide the increment by which it changed. This is intended for incrementally adjusting one property via multiple handlers.
import QtQuick Rectangle { width: 100; height: 100 color: "lightsteelblue"; antialiasing: true PinchHandler { id: handler target: null xAxis.onActiveValueChanged: (delta) => parent.radius -= delta yAxis.onActiveValueChanged: (delta) => parent.border.width += delta rotationAxis.onActiveValueChanged: (delta) => parent.rotation += delta // add scaleAxis.onActiveValueChanged: (delta) => parent.scale *= delta // multiply } WheelHandler { acceptedModifiers: Qt.NoModifier property: "rotation" } WheelHandler { acceptedModifiers: Qt.ControlModifier property: "scale" } }
Note: The snippet is contrived: PinchHandler already knows how to move, scale and rotate its parent item, but this code achieves different behavior in a less-declarative way, to illustrate how to use activeValueChanged
in special cases.
[read-only] scale : QVector2D |
\readonly
\deprecated
[6.5] Use persistentScale
scaleAxis
controls the constraints for setting the scale of the target item according to the distance between the touchpoints.
minimum
is the minimum acceptable scale. maximum
is the maximum acceptable scale. If enabled
is true, scaling is allowed. activeValue
is the same as QtQuick::PinchHandler::activeScale.
The activeValueChanged
signal is emitted when activeValue
changes, to provide the multiplier for the incremental change. This is intended for incrementally adjusting one property via multiple handlers.
import QtQuick Rectangle { width: 100; height: 100 color: "lightsteelblue"; antialiasing: true PinchHandler { id: handler target: null xAxis.onActiveValueChanged: (delta) => parent.radius -= delta yAxis.onActiveValueChanged: (delta) => parent.border.width += delta rotationAxis.onActiveValueChanged: (delta) => parent.rotation += delta // add scaleAxis.onActiveValueChanged: (delta) => parent.scale *= delta // multiply } WheelHandler { acceptedModifiers: Qt.NoModifier property: "rotation" } WheelHandler { acceptedModifiers: Qt.ControlModifier property: "scale" } }
Note: The snippet is contrived: PinchHandler already knows how to move, scale and rotate its parent item, but this code achieves different behavior in a less-declarative way, to illustrate how to use activeValueChanged
in special cases.
[read-only] translation : QVector2D |
\readonly
\deprecated
[6.5] Use activeTranslation
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.
The activeValueChanged
signal is emitted when activeValue
changes, to provide the increment by which it changed. This is intended for incrementally adjusting one property via multiple handlers.
import QtQuick Rectangle { width: 100; height: 100 color: "lightsteelblue"; antialiasing: true PinchHandler { id: handler target: null xAxis.onActiveValueChanged: (delta) => parent.radius -= delta yAxis.onActiveValueChanged: (delta) => parent.border.width += delta rotationAxis.onActiveValueChanged: (delta) => parent.rotation += delta // add scaleAxis.onActiveValueChanged: (delta) => parent.scale *= delta // multiply } WheelHandler { acceptedModifiers: Qt.NoModifier property: "rotation" } WheelHandler { acceptedModifiers: Qt.ControlModifier property: "scale" } }
Note: The snippet is contrived: PinchHandler already knows how to move, scale and rotate its parent item, but this code achieves different behavior in a less-declarative way, to illustrate how to use activeValueChanged
in special cases.
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.
The activeValueChanged
signal is emitted when activeValue
changes, to provide the increment by which it changed. This is intended for incrementally adjusting one property via multiple handlers.
import QtQuick Rectangle { width: 100; height: 100 color: "lightsteelblue"; antialiasing: true PinchHandler { id: handler target: null xAxis.onActiveValueChanged: (delta) => parent.radius -= delta yAxis.onActiveValueChanged: (delta) => parent.border.width += delta rotationAxis.onActiveValueChanged: (delta) => parent.rotation += delta // add scaleAxis.onActiveValueChanged: (delta) => parent.scale *= delta // multiply } WheelHandler { acceptedModifiers: Qt.NoModifier property: "rotation" } WheelHandler { acceptedModifiers: Qt.ControlModifier property: "scale" } }
Note: The snippet is contrived: PinchHandler already knows how to move, scale and rotate its parent item, but this code achieves different behavior in a less-declarative way, to illustrate how to use activeValueChanged
in special cases.
Signal Documentation
rotationChanged(qreal delta) |
The rotationChanged
signal is emitted when activeRotation (and therefore persistentRotation) changes. The delta value gives the additive change in rotation. For example, if the user moves fingers to change the pinch distance so that activeRotation
changes from 10 to 30 degrees, rotationChanged(20)
will be emitted. You can use that to incrementally change the rotation of an item:
import QtQuick Rectangle { width: 100; height: 100 color: "lightsteelblue" PinchHandler { id: handler target: null onRotationChanged: (delta) => parent.rotation += delta // add onScaleChanged: (delta) => parent.scale *= delta // multiply } }
Note: If you set the persistentRotation property directly, delta
is 0
.
Note: The corresponding handler is onRotationChanged
.
scaleChanged(qreal delta) |
The scaleChanged
signal is emitted when activeScale (and therefore persistentScale) changes. The delta value gives the multiplicative change in scale. For example, if the user moves fingers to change the pinch distance so that activeScale
changes from 2 to 2.5, scaleChanged(1.25)
will be emitted. You can use that to incrementally change the scale of an item:
import QtQuick Rectangle { width: 100; height: 100 color: "lightsteelblue" PinchHandler { id: handler target: null onRotationChanged: (delta) => parent.rotation += delta // add onScaleChanged: (delta) => parent.scale *= delta // multiply } }
Note: If you set the persistentScale property directly, delta
is 1
.
Note: The corresponding handler is onScaleChanged
.
translationChanged(QVector2D delta) |
The translationChanged
signal is emitted when activeTranslation (and therefore persistentTranslation) changes. The delta vector gives the change in translation. You can use that to incrementally change the position of an item:
import QtQuick Window { width: 320; height: 240 visible: true title: handler.persistentRotation.toFixed(1) + "° " + handler.persistentTranslation.x.toFixed(1) + ", " + handler.persistentTranslation.y.toFixed(1) + " " + (handler.persistentScale * 100).toFixed(1) + "%" PinchHandler { id: handler target: null persistentScale: 0.25 onTranslationChanged: (delta) => { image.x -= delta.x image.y -= delta.y } } Image { id: image source: "images/album-cover.jpg" scale: handler.persistentScale x: -600; y: -450 } }
Note: If you set the persistentTranslation property directly, delta
is 0, 0
.
Note: The corresponding handler is onTranslationChanged
.