HoverHandler QML Type

Handler for mouse and tablet hover. More...

Import Statement: import QtQuick
Inherits:

SinglePointHandler

Properties

Signals

Detailed Description

HoverHandler detects a hovering mouse or tablet stylus cursor.

A binding to the hovered property is the easiest way to react when the cursor enters or leaves the parent Item. The point property provides more detail, including the cursor position. The acceptedDevices, acceptedPointerTypes, and acceptedModifiers properties can be used to narrow the behavior to detect hovering of specific kinds of devices or while holding a modifier key.

The cursorShape property allows changing the cursor whenever hovered changes to true.

See also MouseArea and PointHandler.

Property Documentation

acceptedDevices : flags

The types of pointing devices that can activate the pointer handler.

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

For example, an item could be made to respond to mouse hover in one way, and stylus hover in another way, with two handlers:

import QtQuick

Rectangle {
    width: 150; height: 50; radius: 3
    color: mouse.hovered ? "goldenrod" : stylus.hovered ? "tomato" : "wheat"

    HoverHandler {
        id: stylus
        acceptedDevices: PointerDevice.Stylus
        cursorShape: Qt.CrossCursor
    }

    HoverHandler {
        id: mouse
        acceptedDevices: PointerDevice.Mouse
        cursorShape: Qt.PointingHandCursor
    }
}

The available device types are as follows:

ConstantDescription
PointerDevice.MouseA mouse.
PointerDevice.TouchScreenA touchscreen.
PointerDevice.TouchPadA touchpad or trackpad.
PointerDevice.StylusA stylus on a graphics tablet.
PointerDevice.AirbrushAn airbrush on a graphics tablet.
PointerDevice.PuckA digitizer with crosshairs, on a graphics tablet.
PointerDevice.AllDevicesAny type of pointing device.

See also QInputDevice::DeviceType.


acceptedModifiers : flags

If this property is set, a hover event is handled only if the given keyboard modifiers are pressed. The event is ignored without the modifiers.

This property is set to Qt.KeyboardModifierMask by default, resulting in handling hover events regardless of any modifier keys.

For example, an Item could have two handlers of the same type, one of which is enabled only if the required keyboard modifiers are pressed:

import QtQuick

Rectangle {
    width: 150; height: 50; radius: 3
    color: control.hovered ? "goldenrod" : shift.hovered ? "wheat" : "beige"

    HoverHandler {
        id: control
        acceptedModifiers: Qt.ControlModifier
        cursorShape: Qt.PointingHandCursor
    }

    HoverHandler {
        id: shift
        acceptedModifiers: Qt.ShiftModifier
        cursorShape: Qt.CrossCursor
    }
}

The available modifiers are as follows:

ConstantDescription
Qt.NoModifierNo modifier key is allowed.
Qt.ShiftModifierA Shift key on the keyboard must be pressed.
Qt.ControlModifierA Ctrl key on the keyboard must be pressed.
Qt.AltModifierAn Alt key on the keyboard must be pressed.
Qt.MetaModifierA Meta key on the keyboard must be pressed.
Qt.KeypadModifierA keypad button must be pressed.
Qt.GroupSwitchModifierA Mode_switch key on the keyboard must be pressed. X11 only (unless activated on Windows by a command line argument).
Qt.KeyboardModifierMaskThe handler ignores modifier keys.

See also Qt::KeyboardModifier.


acceptedPointerTypes : flags

The types of pointing instruments (generic, stylus, eraser, and so on) that can activate the pointer handler.

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 events.

For example, you could provide feedback by changing the cursor depending on whether a stylus or eraser is hovering over a graphics tablet:

import QtQuick

Rectangle {
    id: rect
    width: 150; height: 150

    HoverHandler {
        id: stylus
        acceptedPointerTypes: PointerDevice.Pen
        cursorShape: Qt.CrossCursor
    }

    HoverHandler {
        id: eraser
        acceptedPointerTypes: PointerDevice.Eraser
        cursorShape: Qt.BlankCursor
        target: Image {
            parent: rect
            source: "images/cursor-eraser.png"
            visible: eraser.hovered
            x: eraser.point.position.x
            y: eraser.point.position.y - 32
        }
    }
}

The available pointer types are as follows:

ConstantDescription
PointerDevice.GenericA mouse or a device that emulates a mouse.
PointerDevice.FingerA finger on a touchscreen (hover detection is unlikely).
PointerDevice.PenA stylus on a graphics tablet.
PointerDevice.EraserAn eraser on a graphics tablet.
PointerDevice.CursorA digitizer with crosshairs, on a graphics tablet.
PointerDevice.AllPointerTypesAny type of pointing device.

See also QPointingDevice::PointerType.


[read-only] active : bool

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 Event Points and actively manipulating its target (if any).


[since 5.15] cursorShape : Qt::CursorShape

This property holds the cursor shape that will appear whenever hovered is true and no other handler is overriding it.

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 of this property is not set, which allows any active handler on the same parent item to determine the cursor shape. This property can be reset to the initial condition by setting it to undefined.

If any handler with defined cursorShape is active, that cursor will appear. Else if the HoverHandler has a defined cursorShape, that cursor will appear. Otherwise, the cursor of parent item will appear.

Note: When this property has not been set, or has been set to undefined, if you read the value it will return Qt.ArrowCursor.

This property was introduced in Qt 5.15.

See also Qt::CursorShape and QQuickItem::cursor().


[since 5.15] dragThreshold : int

The distance in pixels that the user must drag an event point 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.


enabled : bool

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


grabPermissions : flags

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.

ConstantDescription
PointerHandler.TakeOverForbiddenThis handler neither takes from nor gives grab permission to any type of Item or Handler.
PointerHandler.CanTakeOverFromHandlersOfSameTypeThis handler can take the exclusive grab from another handler of the same class.
PointerHandler.CanTakeOverFromHandlersOfDifferentTypeThis handler can take the exclusive grab from any kind of handler.
PointerHandler.CanTakeOverFromItemsThis handler can take the exclusive grab from any type of Item.
PointerHandler.CanTakeOverFromAnythingThis handler can take the exclusive grab from any type of Item or Handler.
PointerHandler.ApprovesTakeOverByHandlersOfSameTypeThis handler gives permission for another handler of the same class to take the grab.
PointerHandler.ApprovesTakeOverByHandlersOfDifferentTypeThis handler gives permission for any kind of handler to take the grab.
PointerHandler.ApprovesTakeOverByItemsThis handler gives permission for any kind of Item to take the grab.
PointerHandler.ApprovesCancellationThis handler will allow its grab to be set to null.
PointerHandler.ApprovesTakeOverByAnythingThis handler gives permission for any any type of Item or Handler to take the grab.

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.


[read-only] hovered : bool

Holds true whenever any pointing device cursor (mouse or tablet) is within the bounds of the parent Item, extended by the margin, if any.


margin : real

The margin beyond the bounds of the parent item within which an event point can activate this handler. For example, on a PinchHandler where the target is also the parent, it's useful to set this to a distance at least half the width of a typical user's finger, so that if the parent has been scaled down to a very small size, the pinch gesture is still possible. Or, if a TapHandler-based button is placed near the screen edge, it can be used to comply with Fitts's Law: react to mouse clicks at the screen edge even though the button is visually spaced away from the edge by a few pixels.

The default value is 0.


[read-only] parent : Item

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 event points occurs within the Item's interior. Initially target() is the same, but it can be reassigned.

Note: When a handler is declared in a QtQuick3D.Model object, the parent is not an Item, therefore this property is null.

See also target and QObject::parent().


[read-only] point : HandlerPoint

The event point currently being handled. When no point is currently being handled, this object is reset to default values (all coordinates are 0).


target : Item

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.


Signal Documentation

canceled(EventPoint point)

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.


grabChanged(GrabTransition transition, EventPoint point)

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.


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