SetWindowModified with QGraphicsView, is it bug?

[ZapB]

I have confirmed on IRC that this is indeed a bug in Qt. I'll file a bug report and let you know where it is. In the interim just use the above work around.

[ZapB]

I have filed a bug in JIRA. You can find it at http://bugreports.qt.nokia.com/browse/QTBUG-20150

[maherali]

Thank you ZapB, it's really weird I'm working with qt for 1 month, it's too early to find such a bug.

Regards

[ZapB]

I think it is a regression (judging by comments on other related bug reports). If I get the time I'll see about making a patch to fix it.

[maherali]

I'll try to emit the events manually, I need sometime to read about Events mechanisms in Qt and let you know, thanks

[ZapB]

Something like this should do it:

In your YPeersView headr file add a new sceneModified() signal:

@
class YPeersView : public QGraphicsView {
Q_OBJECT
public:
...

signals:
void sceneModified();

...

};
@

Be sure to emit this in you handler instead of calling setWindowModified:
@
YPeerNode* YPeersView::addNode(QPointF pos)
{
YPeerNode* node=new YPeerNode(5);
node->setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsSelectable);

if(scene())
{
    scene()->addItem(node);
    scene()->clearSelection();
    
    /** \bug In Qt - work around using custom signal */
    //setWindowModified(true);
    emit sceneModified();

    node->update();       
    itemsCountChanged(scene()->items().count());
    return node;
}
return 0;

}
@

In your mainwindow header add a new slot to handle this signal:

@
class MainWindow : public QMainWindow {
Q_OBJECT
public:
...

public slots:
void onSceneModified() { setWindowModified( true ); }
};
@

And finally make the connection in your mainwindow ctor (or somewhere else convenient):

@
MainWindow::MainWindow( QWidget* parent )
: QMainWindow( parent )
{
...
connect( m_view, SIGNAL( sceneModified() ), this, SLOT( onSceneModified() ) );
}
@

That should do it I think.

[maherali]

Thanks ZapB
I'm already using Signals/Slots to notify the parent that the scene items number has been changed
but I was working on implementing events handlers (custom events)
I've read that signals/slots don't use separate threads which means non-responsive program.

I'll try to call events, if it didn't work I'll use the signal/slot mechanism.

[maherali]

Hi
I did it using the events
My custom event
@
class YChangedEvent : public QEvent
{
public:
YChangedEvent();
};
@

in the view custom class I use this function
@
void YPeersView::sceneStateChanged()
{
QApplication::postEvent(parent(),new YChangedEvent());
}
@

in the Mainwindow
@
void YPeerScenarioWidget::customEvent(QEvent *e)
{

if(e->type()==YEvents::YCHANGEDEVENT)
{
    setWindowModified(true);
}

}

@

it works, thanks ZapB
I think I started to love Qt more than C#

[ZapB]

Yeah either approach will work. Signals/slots work just like direct function calls if both objects have affinity with the same thread (which yours do form the loosk of things). If the sender and receiver are affine with different threads then the signal/slot mechanism actually uses QEvents behined the scenes and the slot works asynchronously.

Of course if you are comfortable using custom events yourself then either approach works perfectly fine.

Glad you got it working anyway. Have fun with the rest of your project.

[maherali]

Oh that's good point, Slots/Signals mechanism is really flexible.
It will save us lot of time.

Thanks for your help