QPinchGesture Class Reference

The QPinchGesture class describes a pinch gesture made by the user.

  1. #include <QPinchGesture>

Inherits: QGesture.

This class was introduced in Qt 4.6.

Detailed Description

The QPinchGesture class describes a pinch gesture made by the user.

A pinch gesture is a form of touch user input in which the user typically touches two points on the input device with a thumb and finger, before moving them closer together or further apart to change the scale factor, zoom, or level of detail of the user interface.

For an overview of gesture handling in Qt and information on using gestures in your applications, see the Gestures Programming document.

Instead of repeatedly applying the same pinching gesture, the user may continue to touch the input device in one place, and apply a second touch to a new point, continuing the gesture. When this occurs, gesture events will continue to be delivered to the target object, containing an instance of QPinchGesture in the Qt::GestureUpdated state.

See also QPanGesture and QSwipeGesture.

Public Types

Toggle detailsenum QPinchGesture::

ChangeFlagChangeFlag { ScaleFactorChanged , RotationAngleChanged , CenterPointChanged 0x4 ...} { ScaleFactorChanged , RotationAngleChanged , CenterPointChanged 0x4 }

This enum describes the changes that can occur to the properties of the gesture object.

ConstantValueDescription
QPinchGesture::ScaleFactorChanged 0x1 The scale factor held by scaleFactor changed.
QPinchGesture::RotationAngleChanged 0x2 The rotation angle held by rotationAngle changed.
QPinchGesture::CenterPointChanged 0x4 The center point held by centerPoint changed.

See also changeFlags and totalChangeFlags.

Look up this member in the source code.

    Properties

    Toggle detailscenterPointcenterPoint : QPointF

    This property holds the current center point

    The center point is the midpoint between the two input points in the gesture.

    See also startCenterPoint and lastCenterPoint.

    Access functions:

    Look up this member in the source code.

    Toggle detailschangeFlagschangeFlags : ChangeFlags

    This property holds the property of the gesture that has changed in the current step

    This property indicates which of the other properties has changed since the previous gesture event included information about this gesture. You can use this information to determine which aspect of your user interface needs to be updated.

    See also totalChangeFlags, scaleFactor, rotationAngle, and centerPoint.

    Access functions:

    Look up this member in the source code.

    Toggle detailslastCenterPointlastCenterPoint : QPointF

    This property holds the last position of the center point recorded for this gesture

    See also centerPoint and startCenterPoint.

    Access functions:

    Look up this member in the source code.

    Toggle detailslastRotationAnglelastRotationAngle : qreal

    This property holds the last reported angle covered by the gesture motion

    The last rotation angle is the angle as reported in the rotationAngle property when a previous gesture event was delivered for this gesture.

    See also rotationAngle and totalRotationAngle.

    Access functions:

    Look up this member in the source code.

    Toggle detailslastScaleFactorlastScaleFactor : qreal

    This property holds the last scale factor recorded for this gesture

    The last scale factor contains the scale factor reported in the scaleFactor property when a previous gesture event included information about this gesture.

    If no previous event was delivered with information about this gesture (i.e., this gesture object contains information about the first movement in the gesture) then this property contains zero.

    See also scaleFactor and totalScaleFactor.

    Access functions:

    Look up this member in the source code.

    Toggle detailsrotationAnglerotationAngle : qreal

    This property holds the angle covered by the gesture motion

    See also totalRotationAngle and lastRotationAngle.

    Access functions:

    Look up this member in the source code.

    Toggle detailsscaleFactorscaleFactor : qreal

    This property holds the current scale factor

    The scale factor measures the scale factor associated with the distance between two of the user's inputs on a touch device.

    See also totalScaleFactor and lastScaleFactor.

    Access functions:

    Look up this member in the source code.

    Toggle detailsstartCenterPointstartCenterPoint : QPointF

    This property holds the starting position of the center point

    See also centerPoint and lastCenterPoint.

    Access functions:

    Look up this member in the source code.

    Toggle detailstotalChangeFlagstotalChangeFlags : ChangeFlags

    This property holds the property of the gesture that has change

    This property indicates which of the other properties has changed since the gesture has started. You can use this information to determine which aspect of your user interface needs to be updated.

    See also changeFlags, scaleFactor, rotationAngle, and centerPoint.

    Access functions:

    Look up this member in the source code.

    Toggle detailstotalRotationAngletotalRotationAngle : qreal

    This property holds the total angle covered by the gesture

    This total angle measures the complete angle covered by the gesture. Usually, this is equal to the value held by the rotationAngle property, except in the case where the user performs multiple rotations by removing and repositioning one of the touch points, as described above. In this case, the total angle will be the sum of the rotation angles for the multiple stages of the gesture.

    See also rotationAngle and lastRotationAngle.

    Access functions:

    Look up this member in the source code.

    Toggle detailstotalScaleFactortotalScaleFactor : qreal

    This property holds the total scale factor

    The total scale factor measures the total change in scale factor from the original value to the current scale factor.

    See also scaleFactor and lastScaleFactor.

    Access functions:

    Look up this member in the source code.

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