Allow PinchHandler to maintain its transformation state when it has no target

I'm experimenting with PinchHandler in order to make a canvas zoomable using pinch gestures. The canvas has its own zoomLevel property, so it doesn't make sense to modify its scale property. For that reason, I set the handler's target to null. The problem I encountered with this is that each pinch starts from the default scale (1), rather than persisting across pinches. A simple workaround for this is to use an empty Item:

PinchHandler {
    target: pinchStateItem
}

// ...

Item {
    id: pinchStateItem
    onScaleChanged: if (canvas) canvas.currentPane.setZoomLevel(scale)
}

I think it would be useful if PinchHandler maintained its transformation state when it has no target. I can't think of a scenario where you'd want to discard the state between pinches, but if there are valid use cases for that, a property would work too:

PinchHandler {
    target: null
    maintainState: true
    // persistent: true
    // persistentState: true
    // persistState: true
}