How to prevent a QGraphicsItem from getting mousePressEvent from higher QGraphicsItem?

[Niagarer]

Hey,
I want, that a QGraphicsItem, which is lying behind another QGraphicsItem in a QGraphicsScene, does not get his mousePressEvent triggered, when the mousePressEvent of the higher QGraphicsItem is triggered.
Or in other words: How to make sure, that only the highest visible QGraphicsItem I click on gets the mousePressEvent triggered?
Thanks for answers!

[Niagarer]

@mrjj
Wooow, I just wrote mouseMoveEvent 2 minutes ago, copy and paste mistake.
Yes it works now, so the actual thing was the usage of QGraphicsSceneMouseEvent. And yes, the mousePressEvent of the item behind it, does not get triggered, wonderful.
Wonderful, thank you very much!

To sum it up:

#include <QGraphicsSceneMouseEvent>
void myQGraphicsItem::mousePressEvent(QGraphicsSceneMouseEvent *event){
    QGraphicsItem::mousePressEvent(event); // call base
    // do stuff
    event->accept(); say its handled, so the items behind dont get the mouseClick
}

@mrjj said in How to prevent a QGraphicsItem from getting mousePressEvent from higher QGraphicsItem?:

This goes for all Event type functions
if you say
event->accept();
you say "i handled it" and Qt will not try to give it to others

[mrjj]

I think you can just eat it at the top level
void MyGraphicsItem ::mousePressEvent(QMouseEvent* event)
{
QGraphicsItem ::mousePressEvent(event); // call base
... your code..
event->accept(); // say its handled
}

But i didnt test it

[Niagarer]

@mrjj
Ok, but

QGraphicsItem::mousePressEvent(event);

causes an error...

error: no matching function for call to 'myQGraphicsItemClass::mousePressEvent(QMouseEvent*&)'
     QGraphicsItem::mousePressEvent(event);
                                         ^

I cleaned, ran qmake, rebuilt, added all needed includes, declared mousePressEvent in the .h ...
interesting...

[mrjj]

did u declare it as
(QMouseEvent* event)

as
myQGraphicsItemClass::mousePressEvent(QMouseEvent*&)

looks odd , the * & part

[Niagarer]

@mrjj
Yes, like so:

void myQGraphicsItemClass::mousePressEvent(QMouseEvent *event){
    QGraphicsItem::mousePressEvent(event);
    qDebug() << "mouse pressed";
    event->accept();
}

[mrjj]

@Niagarer
and in .h its
protected:
virtual void mousePressEvent(QMouseEvent *event) override;

[mrjj]

Ah sorry
its
void QGraphicsItem::mousePressEvent(QGraphicsSceneMouseEvent * event)

the other syntax is for QWidgets

So its other type of event class. else concept should be the same
so just change QMouseEvent to QGraphicsSceneMouseEvent and we
are in business i hope.

http://doc.qt.io/qt-5/qgraphicsitem.html#mousePressEvent

[Niagarer]

@mrjj
Ah, ok, I see, let me try...

[Niagarer]

@mrjj
It doesn't work... the mousePressEvent gets not executed... hm...
Or I am stupid, I don't know...

[mrjj]

@Niagarer
you are not stupid. :)

make sure you have
virtual void mousePressEvent(QGraphicsSceneMouseEvent *event) override;
in h.

notice the override.
it should say if its not really overriding it

[Niagarer]

@mrjj
Yes, that is exactely what I wrote...
Oh wait...

[mrjj]

@Niagarer
hmm hmm
And no erros or warning ?

[mrjj]

They use it here
http://doc.qt.io/qt-5/qtwidgets-graphicsview-elasticnodes-example.html

[Niagarer]

@mrjj
Wooow, I just wrote mouseMoveEvent 2 minutes ago, copy and paste mistake.
Yes it works now, so the actual thing was the usage of QGraphicsSceneMouseEvent. And yes, the mousePressEvent of the item behind it, does not get triggered, wonderful.
Wonderful, thank you very much!

To sum it up:

#include <QGraphicsSceneMouseEvent>
void myQGraphicsItem::mousePressEvent(QGraphicsSceneMouseEvent *event){
    QGraphicsItem::mousePressEvent(event); // call base
    // do stuff
    event->accept(); say its handled, so the items behind dont get the mouseClick
}

@mrjj said in How to prevent a QGraphicsItem from getting mousePressEvent from higher QGraphicsItem?:

This goes for all Event type functions
if you say
event->accept();
you say "i handled it" and Qt will not try to give it to others

[mrjj]

Oh sorry, it was my bad, i pasted the wrong one before. I guess u copied it and
like me didnt see it was move and not press :)
Good it works !

This goes for all Event type functions
if you say
event->accept();
you say "i handled it" and Qt will not try to give it to others