Problem with QGraphicsScene mouse move event

Hello,

I re-implement mouse event handlers in a subclass of QGraphicsScene and have a problem with the mouseMoveEvent() function.

The following code works (i.e. when I press the left/middle/right buttons, hold and move, I have the text displayed):

Code:

---

void Scene::mouseMoveEvent(QGraphicsSceneMouseEvent* e)
{
	std::cout<<"hehe"<<std::endl;
}

---

but the following does not (nothing happens even if I press the left button):

Code:

---

void Scene::mouseMoveEvent(QGraphicsSceneMouseEvent* e)
{
	if(e->button()==Qt::LeftButton) std::cout<<"hehe"<<std::endl;
}

---

The following code also works

Code:

---

void Scene::mousePressEvent(QGraphicsSceneMouseEvent* e){
	if(e->button()==Qt::LeftButton) std::cout<<"hehe"<<std::endl;
}

---

Hope it's not a bug of Qt and somebody can help.
Thank you so much.

QGraphicsSceneMouseEvent::button() returns the mouse button that causes the event to happen. Since mouse movement is not related to pressing a mouse button, button() probably returns Qt::NoButton. Try this instead:

Code:

---

if(e->buttons() & Qt::LeftButton) { ... }

---

Works like a charm. Thanks, wysota :D