[Qt-qml] Forwarding mouse events to MouseArea underneath

[Gregory Schlomoff]

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

Yeah, you'd think that's what this property was made for. And you'd be wrong :)

MouseEvent.accepted seems perfectly useless, but in very specific
cases, like in onDoubleClicked.

http://doc.qt.nokia.com/main-snapshot/qml-mousearea.html#onClicked-signal
--> "The accepted property of the MouseEvent parameter is ignored in
this handler."


On Fri, Jan 7, 2011 at 5:50 PM, Juha Turunen <turunen at iki.fi> wrote:
> 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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>> Qt-qml at qt.nokia.com
>> http://lists.qt.nokia.com/mailman/listinfo/qt-qml
>>
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