Qt-interest Archive, November 2006
Re: QGraphicsView misses updates
Message 1 in thread
Thanks for the hints. I must be doing something wrong, because even your
hint did nothing. Is this a problem that I am doing the updates to the
QGraphicsItem during a mouse move event? What is odd is that if I move
items it will work just fine, its only when I try to draw a line from the
start point, to my current mouse point.
thx
-ian reinhart geiser
Courtland Idstrom wrote:
> Are you calling QGraphicsView->update() -- I think this method
> doesn't invalidate regions that need repainting. You might want to
> use QGraphicsView::updateScene() instead. Are you relying on
> QGraphicsItem to send updates when necessary (I believe this is
> recommended and does work correctly)?
>
> However, I have found that when lots of update rectangles are posted
> (which happens when many objects are moving at the same time),
> updates are very slow. I've submitted a bug report regarding this,
> but in the meantime, you can easily overcome this issue by overriding
> QGraphicsView::paintEvent() in your subclass with this:
>
> void YourClass::paintEvent(QPaintEvent *event) {
> QPaintEvent adjusted = *event;
>
> if(event->region().rects().size() > 10) {
> QRect rect = event->region().boundingRect().adjusted(-1,-1,1,1);
> adjusted = QPaintEvent(rect);
> }
>
> QGraphicsView::paintEvent(&adjusted);
> return;
> }
>
> When confronted with a large number of update rectangles, this sends
> only the boundingRect() of all regions posted in the paintEvent.
>
> Cheers
> -Court
>
> On Oct 30, 2006, at 11:40 AM, Ian Reinhart Geiser wrote:
>
>> Dimitri wrote:
>>
>>> Hi,
>>>
>>>> I have a problem with getting the QGraphicsView to
>>>> update. It
>>>> seems very
>>>> unreliable when I change the graphics item, and then call
>>>> update. This
>>>> is most obvious when I am doing drag operations and need to
>>>> update the
>>>> objects
>>>> on the screen while the drag operation is in effect. Does anyone
>>>> have
>>>> some hints on how to cause the graphics view to update without
>>>> bogging
>>>> down the system. (No update is a miserable failure)
>>>
>>> On which platform exactly?
>> WinXP (local & rdesktop), Linux (Ubuntu with Xorg 7.0.0, and SuSE
>> 10.1 with
>> Xorg 6.9), Win2K and Win2003 terminal services session. I have not
>> tested
>> MacOSX yet, but should be able to do so tonight.
>> -ian reinhart geiser
>>
>> --
>> To unsubscribe - send a mail to qt-interest-request@xxxxxxxxxxxxx
>> with "unsubscribe" in the subject or the body.
>> List archive and information: http://lists.trolltech.com/qt-interest/
>>
>>
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Message 2 in thread
Not sure if this is your problem or not but a long time ago I
had similiar problems because I was calling the View's update
instead of the canvas update (now called QGraphicsScene::update()).
Try calling the scene's ::update(sceneRect())
Jeff
On Tue, 2006-10-31 at 22:12 -0500, Ian Reinhart Geiser wrote:
> Thanks for the hints. I must be doing something wrong, because even your
> hint did nothing. Is this a problem that I am doing the updates to the
> QGraphicsItem during a mouse move event? What is odd is that if I move
> items it will work just fine, its only when I try to draw a line from the
> start point, to my current mouse point.
>
> thx
> -ian reinhart geiser
>
>
> Courtland Idstrom wrote:
>
> > Are you calling QGraphicsView->update() -- I think this method
> > doesn't invalidate regions that need repainting. You might want to
> > use QGraphicsView::updateScene() instead. Are you relying on
> > QGraphicsItem to send updates when necessary (I believe this is
> > recommended and does work correctly)?
> >
> > However, I have found that when lots of update rectangles are posted
> > (which happens when many objects are moving at the same time),
> > updates are very slow. I've submitted a bug report regarding this,
> > but in the meantime, you can easily overcome this issue by overriding
> > QGraphicsView::paintEvent() in your subclass with this:
> >
> > void YourClass::paintEvent(QPaintEvent *event) {
> > QPaintEvent adjusted = *event;
> >
> > if(event->region().rects().size() > 10) {
> > QRect rect = event->region().boundingRect().adjusted(-1,-1,1,1);
> > adjusted = QPaintEvent(rect);
> > }
> >
> > QGraphicsView::paintEvent(&adjusted);
> > return;
> > }
> >
> > When confronted with a large number of update rectangles, this sends
> > only the boundingRect() of all regions posted in the paintEvent.
> >
> > Cheers
> > -Court
> >
> > On Oct 30, 2006, at 11:40 AM, Ian Reinhart Geiser wrote:
> >
> >> Dimitri wrote:
> >>
> >>> Hi,
> >>>
> >>>> I have a problem with getting the QGraphicsView to
> >>>> update. It
> >>>> seems very
> >>>> unreliable when I change the graphics item, and then call
> >>>> update. This
> >>>> is most obvious when I am doing drag operations and need to
> >>>> update the
> >>>> objects
> >>>> on the screen while the drag operation is in effect. Does anyone
> >>>> have
> >>>> some hints on how to cause the graphics view to update without
> >>>> bogging
> >>>> down the system. (No update is a miserable failure)
> >>>
> >>> On which platform exactly?
> >> WinXP (local & rdesktop), Linux (Ubuntu with Xorg 7.0.0, and SuSE
> >> 10.1 with
> >> Xorg 6.9), Win2K and Win2003 terminal services session. I have not
> >> tested
> >> MacOSX yet, but should be able to do so tonight.
> >> -ian reinhart geiser
> >>
> >> --
> >> To unsubscribe - send a mail to qt-interest-request@xxxxxxxxxxxxx
> >> with "unsubscribe" in the subject or the body.
> >> List archive and information: http://lists.trolltech.com/qt-interest/
> >>
> >>
>
> --
> To unsubscribe - send a mail to qt-interest-request@xxxxxxxxxxxxx with "unsubscribe" in the subject or the body.
> List archive and information: http://lists.trolltech.com/qt-interest/
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