[Qt-qml] Apply Transform to Item in onChildrenChanged?

[michael.brasser at nokia.com]

Hi Charley,

On 22/10/2010, at 9:36 AM, ext Charley Bay wrote:

> I wrote my own "layout" type class by hooking
> into onChildrenChanged which is triggered on
> parent changed, and it works great:
> 
> Item {
>    id: myItem
>     onChildrenChanged: {
>      myItem.myUpdateChildrenPlacement()
>     }
> 
>     function myUpdateChildrenPlacement() {
>         for(var i= 0; i < myItem.children.length; ++i) {
>          myItem.children[i].x = 13;
>          myItem.children[i].y = 42;
> 
>         // HOW TO APPLY A TRANSFORM? LIKE:
> //NOT WORK:         myItem.children[i].translate += Rotation { ...}
>         }
>     }
> }
> 
> I know the "translate" is read-only, and that you would
> typically define the Rotation{} when you defined the
> (child) item.

I think you mean "transform" here? The following works for me, using HEAD (if it isn't working for you, it may be that a required fix is coming in 4.7.1):

 Rectangle {
    id: wrapper
    width: 200; height: 200
    Rectangle {
        id: rect
        width: 100; height: 100
        color: "green"
        anchors.centerIn: parent
    }
    Rotation {
        id: rot
        angle: 45
    }
    Component.onCompleted: {
        rect.transform = rot
    }
}

However, there isn't any built-in way to *append* to a list property (the rotation would replace any transforms currently on the item). You should be able to use one of the techniques described at http://doc.qt.nokia.com/4.7/qdeclarativedynamicobjects.html to dynamically create a Rotation element for each child.

Just in case you haven't noticed them before, I'll also mention that there are also simple "rotation" and "scale" properties that would be easier to manipulate, assuming you didn't need the full features offered by Rotation, etc.

Regards,
Michael