Mouse Events

handling mouse events in Qt Quick

A more modern way of handling events from all pointing devices, including mouse and touchscreen, is via Input Handlers . This page describes the original Qt Quick MouseArea type, which was initially designed to handle mouse input, and later began handling single-touch events (in the form of synthetic mouse events) in simple touch-oriented user interfaces.

Mouse Types

Mouse Event Handling

QML uses signals and handlers to deliver mouse interactions. Specifically, Qt Quick provides the MouseArea and MouseEvent types that allow developers to define JavaScript callbacks (also called signal handlers), which accept mouse events within a defined area.

Defining a Mouse Area

The MouseArea type receives events within a defined area. One quick way to define this area is to anchor the MouseArea to its parent’s area using the anchors.fill property. If the parent is a Rectangle (or any Item component), then the MouseArea will fill the area defined by the parent’s dimensions. Alternatively, an area smaller or larger than the parent is definable.

Rectangle {
    id: button
    width: 100; height: 100

    MouseArea {
        anchors.fill: parent
        onClicked: console.log("button clicked")
    }
    MouseArea {
        width:150; height: 75
        onClicked: console.log("irregular area clicked")
    }
}

Receiving Events

The MouseArea type emits signals in response to different mouse events. The MouseArea type documentation describes these gestures in greater detail:

  • canceled

  • clicked

  • doubleClicked

  • entered

  • exited

  • positionChanged

  • pressAndHold

  • pressed

  • released

These signals can have callbacks that are invoked when the signals are emitted.

MouseArea {
    anchors.fill: parent
    onClicked: console.log("area clicked")
    onDoubleClicked: console.log("area double clicked")
    onEntered: console.log("mouse entered the area")
    onExited: console.log("mouse left the area")
}

Enabling Gestures

Some mouse gestures and button clicks need to be enabled before they send or receive events. Certain MouseArea and MouseEvent properties enable these gestures.

To listen to (or explicitly ignore) a certain mouse button, set the appropriate mouse button to the acceptedButtons property.

Naturally, the mouse events, such as button presses and mouse positions, are sent during a mouse click. For example, the containsMouse property will only retrieve its correct value during a mouse press. The hoverEnabled will enable mouse events and positioning even when there are no mouse button presses. Setting the hoverEnabled property to true, in turn will enable the entered, exited, and positionChanged signal and their respective signal handlers.

MouseArea {
    hoverEnabled: true
    acceptedButtons: Qt.LeftButton | Qt.RightButton
    onEntered: console.log("mouse entered the area")
    onExited: console.log("mouse left the area")
}

Additionally, to disable the whole mouse area, set the MouseArea enabled property to false.

MouseEvent Object

Signals and their callbacks receive a MouseEvent object as a parameter. The mouse object contains information about the mouse event. For example, the mouse button that started the event is queried through the mouse.button property.

The MouseEvent object can also ignore a mouse event using its accepted property.

Accepting Further Signals

Many of the signals are sent multiple times to reflect various mouse events such as double clicking. To facilitate the classification of mouse clicks, the MouseEvent object has an accepted property to disable the event propagation.

To learn more about QML’s event system, please read the signals and handlers, and event system document.