[Qt-qml] Forwarding mouse events to MouseArea underneath

[Juha Turunen]

http://doc.qt.nokia.com/4.7-snapshot/qml-mouseevent.html#accepted-prop ?

On Fri, Jan 7, 2011 at 11:51 AM, Gregory Schlomoff
<gregory.schlomoff at gmail.com> wrote:
> Hello,
>
> We are in a situation where we have one big MouseArea on top handling
> click events and several smaller MouseAreas below handling
> double-click events.
>
> Unfortunately, there is currently no way in QML to say that an event
> should "bubble" up or down to the next receiver. The top MouseArea
> will always catch all events, and the MouseAreas below will get
> nothing.
>
> There is a very specific solution when the event you want to handle in
> the topmost MouseArea is onDrag. In this case, you can use
> drag.filterChildren: true to let the topmost MouseArea catch only drag
> event and pass other events to MouseAreas beneath. But it won't work
> for other events.
>
> We devised a ugly hack to work around this, that basically involves
> catching the event in the topmost MouseArea and manually calling the
> event handler on any MouseArea underneath:
>
> ===============
> import QtQuick 1.0
>
> Rectangle {
>        width: 360
>        height: 360
>
>        MouseArea {
>                anchors {fill: parent; margins: 40}
>                onClicked: console.log("hello from below");
>        }
>
>        MouseArea {
>                id: mouseArea
>                anchors.fill: parent
>
>                onClicked: {
>                        console.log("hello from top")
>                        forwardEvent(mouse, "clicked");
>                }
>
>                function forwardEvent(event, eventType) {
>                        mouseArea.visible = false
>                        var item = parent.childAt(event.x, event.y)
>                        mouseArea.visible = true
>                        if (item && item != mouseArea && typeof(item[eventType]) == "function") {
>                                item[eventType](event);
>                        }
>                }
>        }
> }
> ===============
>
> What do you think? Are there any better solutions? Should this be a
> built-in functionnality in QML so that we can avoid this hack,
> especially the fact that we have to hide / show the element to get
> elements below. Any feedback is appreciated.
>
> Thanks,
>
> Greg
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