[Qt-qml] Mouse Event Filtering in QML 2

[Adriano Rezende]

2011/6/14 Alan Alpert <alan.alpert at nokia.com>

> On Tue, 14 Jun 2011 23:22:11 ext Adriano Rezende wrote:
> > Sorry, I pressed send by mistake :)
> > In the flickable use case, it's the only way I can see to handle the
> mouse
> > steal. It could be declarative of course, but in that case it would be
> > very specific to a flickable behavior.
> >
>
> What is this 'flickable' use case specifically, and how is it not handled
> by
> the new approach?
>

The flickable use case is not handled by the old approach neither by the new
one (considering what you said). It's a use case where you just need to
filter the press/move/release events from other items, stealing the event
when a drag movement is recognized. Consider the current QML Flickable item
with a button inside; the button shows a highlight on press, but as soon as
the flickable recognizes a drag movement, it will steal the mouse event from
the button, avoiding the release and the click events. Ex.:

Flickable {
    width: 400
    height: 400
    contentHeight: 1000

    Rectangle {
        width: 1000
        height: 1000
        color: mouseArea.pressed ? "red" : "blue"

        MouseArea {
            id: mouseArea
            anchors.fill: parent
            onPressed: print("pressed")
            onClicked: print("clicked") // avoided if dragging
        }
    }
}

Simulating that behavior using a mouse filter would be like below:

MouseFilter {
    width: 400
    height: 400

    onPressed: print("press filtered")
    onPositionChanged: // if dragging, steal mouse

    MouseArea {
        z: -1
        anchors.fill: parent
        onPressed: print("pressed")
        onClicked: print("clicked") // avoided if dragging
    }
}

I thought the new approach would behave like above, which is not the case.
In the end a C++ extension is still needed to handle that, right?

Br,
Adriano
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