Custom items selection in qgraphicsscene

[yonnak]

Hello,
I'm trying to modify default selection behaviour in qgraphicsscene. I'd like to have an event propagation: if a mouse clic occurs on the topmost item, it should be sent to every item under the topmost one.

I try different solutions but can't get it work. Here is my last try in a class derived from QGraphicsScene:

bool myScene::event(QEvent *event)
{
    if ( event->type() == QEvent::GraphicsSceneMousePress ) {
        QGraphicsSceneMouseEvent * me  = (QGraphicsSceneMouseEvent *) event;
        me->setModifiers(Qt::ControlModifier);
        for ( int i = 0; i < items(me->scenePos()).count(); i++ ){
            items(me->scenePos()).at(i)->setFocus(Qt::MouseFocusReason);
            mousePressEvent(me);
        }
        return false;
    }
    QGraphicsScene::event(event);
    return true;
}

bool myScene::event(QEvent *event)
{
    if ( event->type() == QEvent::GraphicsSceneMousePress ) {
        QGraphicsSceneMouseEvent * me  = (QGraphicsSceneMouseEvent *) event;
        me->setModifiers(Qt::ControlModifier);
        for ( int i = 0; i < items(me->scenePos()).count(); i++ ){
            items(me->scenePos()).at(i)->setFocus(Qt::MouseFocusReason);
            mousePressEvent(me);
        }
        return false;
    }
    QGraphicsScene::event(event);
    return true;
}

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Thanks for any help

[Lykurg]

Hi, if you want to deliver events I don't know since graphicsitems has no notify(). [dirty: you could inherit QObject in each item, then use notify] But if you only want to select the items why not just use setSelected:

bool myScene::event(QEvent *event)
{
    if ( event->type() == QEvent::GraphicsSceneMousePress ) {
        QGraphicsSceneMouseEvent * me  = (QGraphicsSceneMouseEvent *) event;
        // test if right or left button is used
        for ( int i = 0; i < items(me->scenePos()).count(); i++ ){
            items(me->scenePos()).at(i)->setSelected(true); //<--
        }
        return false;
    }
    QGraphicsScene::event(event);
    return true;
}

bool myScene::event(QEvent *event)
{
    if ( event->type() == QEvent::GraphicsSceneMousePress ) {
        QGraphicsSceneMouseEvent * me  = (QGraphicsSceneMouseEvent *) event;
        // test if right or left button is used
        for ( int i = 0; i < items(me->scenePos()).count(); i++ ){
            items(me->scenePos()).at(i)->setSelected(true); //<--
        }
        return false;
    }
    QGraphicsScene::event(event);
    return true;
}

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And better cache items(me->scenePos()) instead of performing the "search" in each for-run.

[yonnak]

Hello, thank you for replying.

I have an eventfilter on the items, depending where the clic occurs on the item I move or resize it. So I need to have a mouse event on every item, not only a selection behaviour.

And I will cache the item before the loop!

[aamer4yu]

Still what do u want to achieve with the items below the top item ? What behaviour you want ?
might be it can be done some other way than modifying the current behaviour of graphics view framework

[yonnak]

Yes you are right, there is probably a best way to do what I want.

So here is what i have:
I add line items on my scene, if I clic an extremity of the line, I can rotate/resize it and when I clic any other point of the line, I move it around my scene.

What I want:
If two lines are contiguous, I'd like that clicking on the intersection of the two lines permit to rotate/resize the 2 lines at a time.

If you have a good way to do this...

[Lykurg]

Hi,

I just come across QCoreApplication::postEvent ( QObject * receiver, QEvent * event ). May it help you.

Lykurg

[aamer4yu]

There was a FotoWall example on Qt-apps.org . Search and read the code.
It had features of resizing and rotating graphics item

As for ur case, moving is not a problem, graphics item can move in a scene.. you only need to enable flags for it
as for rotating, the fotowall example might help u

[yonnak]

Hi, thanks for replies!

I can't use QCoreApplication::postEvent ( QObject * receiver, QEvent * event ) since QGraphicsItem does not herites from QObject.

I will take a look at Fotowall, but I have already the resizing, rotating feature working on my items, what I want is to apply this feature at many items at the same time if items are colliding.

I will try again and let you if I find a solution to my problem.