Using both MouseMoveEvent for QGraphicsScene and HoverEnterEvent for QGraphicsItem - qt

Question

I'm trying to create a program in which you can connect points together with lines. I instantiate QGraphicsEllipseItem into a QGraphicsScene and I use HoverEnterEvent and HoverLeaveEvent to change the color and the size of the ellipses when the mouse is over them. To draw a temporary line between the point clicked and the mouse cursor I have to use MouseMoveEvent into the scene. However, when I do that, the HoverEvents of the items don't work anymore ! How can I use both MouseMoveEvent of the scene and HoverEvents of the items ?
void GraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
for (int i = 0; i < pointList.size(); ++i) {
if (pointList[i]->over == 1){
pointList[i]->press();
lineActivated=true;
tempLine.setLine(pointList[i]->x(),pointList[i]->y(),pointList[i]->x(),pointList[i]->y());
}
}
}
void GraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
if(lineActivated){
const QPointF pos = event->scenePos();
tempLine.setP2(pos);
}
}
void Point::hoverEnterEvent(QGraphicsSceneHoverEvent *event)
{
pen.setColor(Qt::green);
pen.setWidth(2);
this->setPen(pen);
over=true;
qDebug("enter");
update();
}
void Point::hoverLeaveEvent(QGraphicsSceneHoverEvent *event)
{
if(isClicked==false){
pen.setColor(Qt::lightGray);
pen.setWidth(1);
over=false;
this->setPen(pen);
qDebug("leave");
update();
}
}

Answer 1

By default QGraphicsScene::mouseMoveEvent sends the necessary information to handle the hover event of the items but override that method you eliminate that behavior. The solution is to call the parent method.
#include <QtWidgets>
class GraphicsScene: public QGraphicsScene{
public:
using QGraphicsScene::QGraphicsScene;
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event){
if(!m_lineitem){
m_lineitem = new QGraphicsLineItem;
addItem(m_lineitem);
}
QLineF l(event->scenePos(), event->scenePos());
m_lineitem->setLine(l);
QGraphicsScene::mousePressEvent(event);
}
void mouseMoveEvent(QGraphicsSceneMouseEvent *event){
if(m_lineitem){
QLineF l(m_lineitem->line().p1(), event->scenePos());
m_lineitem->setLine(l);
}
QGraphicsScene::mouseMoveEvent(event);
}
private:
QGraphicsLineItem *m_lineitem = nullptr;
};
class Point: public QGraphicsEllipseItem{
public:
Point(QGraphicsItem *parent=nullptr): QGraphicsEllipseItem(parent){
setRect(QRectF(-5, -5, 10, 10));
QPen pen;
pen.setColor(Qt::lightGray);
pen.setWidth(1);
setPen(pen);
setAcceptHoverEvents(true);
}
protected:
void hoverEnterEvent(QGraphicsSceneHoverEvent *event){
QPen pen;
pen.setColor(Qt::green);
pen.setWidth(2);
setPen(pen);
QGraphicsEllipseItem::hoverEnterEvent(event);
}
void hoverLeaveEvent(QGraphicsSceneHoverEvent *event){
QPen pen;
pen.setColor(Qt::lightGray);
pen.setWidth(1);
setPen(pen);
QGraphicsEllipseItem::hoverLeaveEvent(event);
}
};
int main(int argc, char *argv[]){
QApplication a(argc, argv);
GraphicsScene *scene = new GraphicsScene;
QGraphicsView w(scene);
w.setRenderHint(QPainter::Antialiasing, true);
w.fitInView(QRectF(0, 0, 100, 100), Qt::KeepAspectRatio);
for(const QPointF & p: {QPointF(10.0, 10.0), QPointF(90.0, 20.0), QPointF(30.0, 40.0)}){
Point *it = new Point();
scene->addItem(it);
it->setPos(p);
}
w.resize(640, 480);
w.show();
return a.exec();
}