Changing mouse cursor in a QObject - QGraphicsItem inherited class - qt

Question

I would like to change my mouse cursor when it is in a graphics item (MyCircle inherits from QObject and QGraphicsItem).
Had my class inherited from QWidget, I would have reimplemented enterEvent() and leaveEvent() and use it as follows :
MyCircle::MyCircle(QObject *parent)
: QWidget(parent), QGraphicsItem() // But I can't
{
rect = QRect(-100,-100,200,200);
connect(this,SIGNAL(mouseEntered()),this,SLOT(in()));
connect(this,SIGNAL(mouseLeft()),this,SLOT(out()));
}
void MyCircle::in()
{
QApplication::setOverrideCursor(Qt::PointingHandCursor);
}
void MyCircle::out()
{
QApplication::setOverrideCursor(Qt::ArrowCursor);
}
void MyCircle::enterEvent(QEvent *)
{
emit mouseEntered();
}
void MyCircle::leaveEvent(QEvent *)
{
emit mouseLeft();
}
Unfortunately, I need to animate that circle (it's a button actually), so I need QObject, is there an easy way to change the cursor ?

Answer 1

QGraphicsItem already has a method for changing the cursor, so you don't need to manually play around with hover events:
QGraphicsItem::setCursor(const QCursor &cursor)
http://doc.qt.io/qt-5/qgraphicsitem.html#setCursor
PS: The dual inheritance of QWidget and QGraphicsItem you do is also a bad idea, only inherit from QGraphicsItem.

Answer 2

You can probably use hover events.
In your class constructor make sure you do...
setAcceptHoverEvents(true);
Then override hoverEnterEvent and hoverLeaveEvent.
virtual void hoverEnterEvent (QGraphicsSceneHoverEvent *event) override
{
QGraphicsItem::hoverEnterEvent(event);
QApplication::setOverrideCursor(Qt::PointingHandCursor);
}
virtual void hoverLeaveEvent (QGraphicsSceneHoverEvent *event) override
{
QGraphicsItem::hoverLeaveEvent(event);
QApplication::setOverrideCursor(Qt::ArrowCursor);
}
As a side note: do you actually inherit from both QObject and QGraphicsItem? If so, you could probably achieve the same goal by simply inheriting from QGraphicsObject.
Edit 1: In answer to...
I have the pointing hand icone in my whole bounding rect, how can I
reduce the area only to my drawing (in this case a circle) ?
Override QGraphicsItem::shape to return a QPainterPath representing the actual shape...
virtual QPainterPath shape () const override
{
QPainterPath path;
/*
* Update path to represent the area in which you want
* the mouse pointer to change. This will probably be
* based on the code in your 'paint' method.
*/
return(path);
}
Now override QGraphicsItem::hoverMoveEvent to make use of the shape method...
virtual void hoverMoveEvent (QGraphicsSceneHoverEvent *event) override
{
QGraphicsItem::hoverMoveEvent(event);
if (shape().contains(event->pos())) {
QApplication::setOverrideCursor(Qt::PointingHandCursor);
} else {
QApplication::setOverrideCursor(Qt::ArrowCursor);
}
}
The above could, obviously, have an impact on performance depending on the complexity of the shape drawn and, hence, the QPainterPath.
(Note: rather than using QGraphicsItem::shape you could do a similar thing with QGraphicsItem::opaque instead.)