[Qt-interest] QgraphicsScene: best way to manage events

[Oliver.Knoll at comit.ch]

On 2010-11-26 ITS-CMT-SUI-SL-SFR-FIN-DEV Knoll Oliver, ITS-CMT-SUI-SL-SFR-FIN-DEV wrote:

>> ...
>> The "most specific" widget/item gets the mouse event first (especially
>> when talking about "mouse hover/move only" events), and only if that
>> widget/item is *not* interested in that event it gets dispatched up
>> the hierarchy, until the root element (the QGraphicsScene for example).
> 
> But those particular events don't bubble all the way up since they're synthesized by
> QGraphicsScene, so its not possible to intercept them at the "global
> QGraphicsScene" level, 

Okay, I think I start to understand what you mean: the events in QGraphicsScene are of type QGraphicsSceneDragDropEvent instead of QDropEvent/QDragEnterEvent etc., so they are not propagated "outside the world of QGraphicsScene".

As a matter of fact I currently also struggle to get a simple drag and drop implemented on my QGraphicsScene. I call setAcceptDrops(true) on the corresponding QGraphicsView, and in my derived QGraphicsScene object the dragEnterEvent(QGraphicsSceneDragDropEvent *event) method is called. Therein I simply call event->acceptProposedAction() in case the event contains the expected MIME type (and I see in the debugger that this code is indeed called) - but my dropEvent(QGraphicsSceneDragDropEvent *event) is never called, and the cursor doesn't even change shape to "drag'n'drop accepted"!

I don't want to hijack this thread here, and I have to think about it a bit more, so I'll come up with concrete questions later on maybe...

Thanks, Oliver
--
Oliver Knoll
Dipl. Informatik-Ing. ETH
COMIT AG - ++41 79 520 95 22