[PyQt] Handling QGraphicsItem snapping outside of itemChange

Devan Richmond devan.richmond at gmail.com
Wed Feb 25 09:45:24 GMT 2015


I've been trying to create a snap to grid type system for QGraphicsScene and
it seems that most solutions rely on altering the item itself in it's itemChange
method. The problem I have with that solution is that it will also affect
what happens when you use QGraphicsItem::setPos

My ideal solution would decouple the items from any notion of grid snapping such
that the QGraphicsScene deals exclusively with the snapping.

    # QGraphicsScene::mouseMoveEvent
    def mouseMoveEvent(self, event):
        # snapping logic
        event.setScenePos(QtCore.QPointF(x, y))

I know that QGraphicsSceneMouseEvent::setScenePos is internal and not public but
 it demonstrates what type of functionality I'm aiming for. Similarly, the
 constructor is also internal so I can't subclass or create a new instance to
 inject my own event.

A kick in the right direction about how to implement something like this without
 using undocumented functions would be much appreciated.


More information about the PyQt mailing list