Redirecting mouse events from a QGraphicsView to a QGraphicsScene

[wysota]

So the poster is wrong?

You can judge that yourself based on the code I provided.

Then what is the correct way to prevent items from being selected in a QGraphicsScene if my graphics scene is in a state where I don't want the user to be able to select items?

The correct way is to remove the ItemIsSelectable flag from the items. Another good way is to not call the base class implementation of mouse events in the scene but then you lose not only selection but also other features such as focus and item moving.

I override the default implementation of QGraphicsScene::mousePressEvent, QGraphicsScene::mouseMoveEvent and QGraphicsScene::mouseReleaseEvent when the scene is in a non-select state and I don't call the base class implementation. Still, I'm able to select items that have QGraphicsItem::ItemIsSelectable enabled by double-clicking them.

Apparently you are doing something wrong. My guess is you didn't override mouseDoubleClickEvent.

#include <QtGui>
 
class GraphicsScene : public QGraphicsScene {
public:
  GraphicsScene() : QGraphicsScene(){}
protected:
  void mousePressEvent(QGraphicsSceneMouseEvent *e) {
 
  }
  void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *e){}
};
 
int main(int argc, char **argv){
  QApplication app(argc, argv);
  GraphicsScene scene;
  QGraphicsView view;
  view.setScene(&scene);
  QGraphicsEllipseItem *item = scene.addEllipse(QRect(0,0,100,50), QPen(Qt::red), Qt::blue);
  item->setFlag(QGraphicsItem::ItemIsSelectable);
  view.show();
  return app.exec();
}

#include <QtGui>

class GraphicsScene : public QGraphicsScene {
public:
  GraphicsScene() : QGraphicsScene(){}
protected:
  void mousePressEvent(QGraphicsSceneMouseEvent *e) {
  
  }
  void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *e){}
};

int main(int argc, char **argv){
  QApplication app(argc, argv);
  GraphicsScene scene;
  QGraphicsView view;
  view.setScene(&scene);
  QGraphicsEllipseItem *item = scene.addEllipse(QRect(0,0,100,50), QPen(Qt::red), Qt::blue);
  item->setFlag(QGraphicsItem::ItemIsSelectable);
  view.show();
  return app.exec();
}

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