[Qt-interest] Non-blocking windows drag-n-drop

[Aron Bierbaum]

I finally got back to looking into my problem and it appears that it
is because my application is manually processing events. Since my
application is updating a scene graph that is being rendered in a
QGraphicsScene once I start dragging, my application loop freezes, but
Qt does continue to pump events. For example my application would do
the following:


while running:
  updateSceneGraph()
  app.processEvents()

The issue that I am seeing is that once a drag starts I don't get any
calls into updateSceneGraph(). I guess that is what I get for manually
pumping the Qt event loop. My only other idea would be to create a
QTimer() temporarily to call back into my application. :(

Thanks,
Aron

On Fri, Aug 21, 2009 at 12:39 AM, Ross
Bencina<rossb-lists at audiomulch.com> wrote:
> Hi Aron
>
> I agree the documentation looks like a problem but I'm doing drag-n-drop
> into a QGraphicsView on Windows using QDrag::exec() and there is no problem
> with updating/redrawing QGraphicsItems while dragging. Also I have other
> QTimer based animation in my QGraphicsView which updates while dragging. I'm
> still using 4.4.3 so perhaps this has changed in 4.5?
>
> Perhaps the cause of your problems is not QDrag at all? Does your code work
> ok on other platforms?
>
> Ross.
>
>
> ----- Original Message ----- From: "Aron Bierbaum" <aronbierbaum at gmail.com>
> To: <qt-interest at trolltech.com>
> Sent: Friday, August 21, 2009 9:19 AM
> Subject: [Qt-interest] Non-blocking windows drag-n-drop
>
>
>> It appears that there is a limitation on Windows where all drag-n-drop
>> operations in Qt are blocking. [1] Is there any known way to get
>> around this? I would like to update the target QGraphicsItem when
>> hovering over it. This does not seem to work because the widgets are
>> not getting rendered. Any ideas on how to work around this?
>>
>> Thanks,
>> Aron
>>
>>
>> [1] http://doc.trolltech.com/4.5/qdrag.html#exec
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>
>