DragHandler QML Type

The mouse buttons that can activate this DragHandler.

By default, this property is set to Qt.LeftButton. It can be set to an OR combination of mouse buttons, and will ignore events from other buttons.

For example, if a component (such as TextEdit) already handles left-button drags in its own way, it can be augmented with a DragHandler that does something different when dragged via the right button:

The types of pointing devices that can activate this DragHandler.

By default, this property is set to PointerDevice.AllDevices. If you set it to an OR combination of device types, it will ignore events from non-matching devices.

If this property is set, it will require the given keyboard modifiers to be pressed in order to react to pointer events, and otherwise ignore them.

For example, two DragHandlers can perform two different drag-and-drop operations, depending on whether the Control modifier is pressed:

GridView {
    id: root
    width: 320
    height: 480
    cellWidth: 80
    cellHeight: 80
    interactive: false

    displaced: Transition {
        NumberAnimation {
            properties: "x,y"
            easing.type: Easing.OutQuad
        }
    }

    model: DelegateModel {
        id: visualModel
        model: 24
        property var dropTarget: undefined
        property bool copy: false
        delegate: DropArea {
            id: delegateRoot

            width: 80
            height: 80

            onEntered: drag => {
                if (visualModel.copy) {
                    if (drag.source !== icon)
                        visualModel.dropTarget = icon
                } else {
                    visualModel.items.move(drag.source.DelegateModel.itemsIndex, icon.DelegateModel.itemsIndex)
                }
            }

            Rectangle {
                id: icon
                objectName: DelegateModel.itemsIndex

                property string text
                Component.onCompleted: {
                    color = Qt.rgba(0.2 + (48 - DelegateModel.itemsIndex) * Math.random() / 48,
                                    0.3 + DelegateModel.itemsIndex * Math.random() / 48,
                                    0.4 * Math.random(),
                                    1.0)
                    text = DelegateModel.itemsIndex
                }
                border.color: visualModel.dropTarget === this ? "black" : "transparent"
                border.width: 2
                radius: 3
                width: 72
                height: 72
                anchors {
                    horizontalCenter: parent.horizontalCenter
                    verticalCenter: parent.verticalCenter
                }

                states: [
                    State {
                        when: dragHandler.active || controlDragHandler.active
                        ParentChange {
                            target: icon
                            parent: root
                        }

                        AnchorChanges {
                            target: icon
                            anchors {
                                horizontalCenter: undefined
                                verticalCenter: undefined
                            }
                        }
                    }
                ]

                Text {
                    anchors.centerIn: parent
                    color: "white"
                    font.pointSize: 14
                    text: controlDragHandler.active ? "+" : icon.text
                }

                DragHandler {
                    id: dragHandler
                    acceptedModifiers: Qt.NoModifier
                    onActiveChanged: if (!active) visualModel.dropTarget = undefined
                }

                DragHandler {
                    id: controlDragHandler
                    acceptedModifiers: Qt.ControlModifier
                    onActiveChanged: {
                        visualModel.copy = active
                        if (!active) {
                            visualModel.dropTarget.text = icon.text
                            visualModel.dropTarget.color = icon.color
                            visualModel.dropTarget = undefined
                        }
                    }
                }

                Drag.active: dragHandler.active || controlDragHandler.active
                Drag.source: icon
                Drag.hotSpot.x: 36
                Drag.hotSpot.y: 36
            }
        }
    }
}

If this property is set to Qt.KeyboardModifierMask (the default value), then the DragHandler ignores the modifier keys.

If you set acceptedModifiers to an OR combination of modifier keys, it means all of those modifiers must be pressed to activate the handler.

The available modifiers are as follows:

See also Qt::KeyboardModifier.

The types of pointing instruments (finger, stylus, eraser, etc.) that can activate this DragHandler.

By default, this property is set to PointerDevice.AllPointerTypes. If you set it to an OR combination of device types, it will ignore events from non-matching devices.

This holds true whenever this Input Handler has taken sole responsibility for handing one or more eventPoints, by successfully taking an exclusive grab of those points. This means that it is keeping its properties up-to-date according to the movements of those eventPoints and actively manipulating its target (if any).

The translation while the drag gesture is being performed. It is 0, 0 when the gesture begins, and increases as the event point(s) are dragged downward and to the right. After the gesture ends, it stays the same; and when the next drag gesture begins, it is reset to 0, 0 again.

This property holds the cursor shape that will appear whenever the mouse is hovering over the parent item while active is true.

The available cursor shapes are:

• Qt.ArrowCursor
• Qt.UpArrowCursor
• Qt.CrossCursor
• Qt.WaitCursor
• Qt.IBeamCursor
• Qt.SizeVerCursor
• Qt.SizeHorCursor
• Qt.SizeBDiagCursor
• Qt.SizeFDiagCursor
• Qt.SizeAllCursor
• Qt.BlankCursor
• Qt.SplitVCursor
• Qt.SplitHCursor
• Qt.PointingHandCursor
• Qt.ForbiddenCursor
• Qt.WhatsThisCursor
• Qt.BusyCursor
• Qt.OpenHandCursor
• Qt.ClosedHandCursor
• Qt.DragCopyCursor
• Qt.DragMoveCursor
• Qt.DragLinkCursor

The default value is not set, which allows the cursor of parent item to appear. This property can be reset to the same initial condition by setting it to undefined.

This property was introduced in Qt 5.15.

See also Qt::CursorShape, QQuickItem::cursor(), and HoverHandler::cursorShape.

The distance in pixels that the user must drag an eventPoint in order to have it treated as a drag gesture.

The default value depends on the platform and screen resolution. It can be reset back to the default value by setting it to undefined. The behavior when a drag gesture begins varies in different handlers.

This property was introduced in Qt 5.15.

If a PointerHandler is disabled, it will reject all events and no signals will be emitted.

This property specifies the permissions when this handler's logic decides to take over the exclusive grab, or when it is asked to approve grab takeover or cancellation by another handler.

The default is PointerHandler.CanTakeOverFromItems | PointerHandler.CanTakeOverFromHandlersOfDifferentType | PointerHandler.ApprovesTakeOverByAnything which allows most takeover scenarios but avoids e.g. two PinchHandlers fighting over the same touchpoints.

The margin beyond the bounds of the parent item within which an eventPoint can activate this handler. For example, you can make it easier to drag small items by allowing the user to drag from a position nearby:

Rectangle {
    width: 24
    height: 24
    border.color: "steelblue"
    Text {
        text: "it's\ntiny"
        font.pixelSize: 7
        rotation: -45
        anchors.centerIn: parent
    }

    DragHandler {
        margin: 12
    }
}

The Item which is the scope of the handler; the Item in which it was declared. The handler will handle events on behalf of this Item, which means a pointer event is relevant if at least one of its eventPoints occurs within the Item's interior. Initially target() is the same, but it can be reassigned.

See also target and QObject::parent().

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 drag gesture is being performed, activeTranslation is continuously added to it; after the gesture ends, it stays the same.

The Item which this handler will manipulate.

By default, it is the same as the parent, the Item within which the handler is declared. However, it can sometimes be useful to set the target to a different Item, in order to handle events within one item but manipulate another; or to null, to disable the default behavior and do something else instead.

xAxis controls the constraints for horizontal dragging.

minimum is the minimum acceptable value of x to be applied to the target. maximum is the maximum acceptable value of x to be applied to the target. If enabled is true, horizontal dragging is allowed.

yAxis controls the constraints for vertical dragging.

minimum is the minimum acceptable value of y to be applied to the target. maximum is the maximum acceptable value of y to be applied to the target. If enabled is true, vertical dragging is allowed.

If this handler has already grabbed the given point, this signal is emitted when the grab is stolen by a different Pointer Handler or Item.

Note: The corresponding handler is onCanceled.

This signal is emitted when the grab has changed in some way which is relevant to this handler.

The transition (verb) tells what happened. The point (object) is the point that was grabbed or ungrabbed.

Note: The corresponding handler is onGrabChanged.