Handling mouse events in QGraphicsWidget subclass

[Asperamanca]

Hi all,

I have written a QGraphicsWidget subclass that should behave like a simple button. As it is, it should show a pixmap, and emit a signal when the left mouse button is pressed on it.

However, I never receive any mouse events. I've re-implemented the mousePressedEvent, but never reach my breakpoint within this event.

I've seen samples doing similar things that work (e.g. in the AnimatedTile example). I do not see a significant difference, and I'd like to understand what I am doing wrong.

Here's the source code, first the header file:

#ifndef BUTTON_H
#define BUTTON_H
 
#include <QGraphicsWidget>
#include <QGraphicsPixmapItem>
 
class Button : public QGraphicsWidget
{
    Q_OBJECT
public:
    explicit Button(QGraphicsItem *parent = 0);
    void setPixmap(const QPixmap pixmap);    
 
signals:
    void pressed(void);
 
public slots:
 
protected:
   void mousePressEvent(QGraphicsSceneMouseEvent* event);
 
   // Tried my own implementations, but no change
   //QRectF boundingRect() const;
   //QPainterPath shape() const;
 
private:
    QGraphicsPixmapItem* _buttonImage;
};
 
#endif // BUTTON_H

#ifndef BUTTON_H
#define BUTTON_H

#include <QGraphicsWidget>
#include <QGraphicsPixmapItem>

class Button : public QGraphicsWidget
{
    Q_OBJECT
public:
    explicit Button(QGraphicsItem *parent = 0);
    void setPixmap(const QPixmap pixmap);    

signals:
    void pressed(void);

public slots:

protected:
   void mousePressEvent(QGraphicsSceneMouseEvent* event);

   // Tried my own implementations, but no change
   //QRectF boundingRect() const;
   //QPainterPath shape() const;

private:
    QGraphicsPixmapItem* _buttonImage;
};

#endif // BUTTON_H

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Now the cpp file:

#include "button.h"
#include <QGraphicsSceneMouseEvent>
 
Button::Button(QGraphicsItem *parent) :
    QGraphicsWidget(parent, 0)
{
    setSizePolicy(QSizePolicy::Fixed,
                  QSizePolicy::Fixed,
                  QSizePolicy::DefaultType);
    setPreferredSize(0,0);
    setAcceptHoverEvents(true);
}
 
void Button::setPixmap(const QPixmap pixmap)
{
    if (!_buttonImage)
        delete _buttonImage;
 
    _buttonImage = new QGraphicsPixmapItem(pixmap, this);
    _buttonImage->setPos(0,0);
    setPreferredSize(_buttonImage->pixmap().width(),
                     _buttonImage->pixmap().height());
}
 
void Button::mousePressEvent(QGraphicsSceneMouseEvent* event)
{
    if ((event->button() == Qt::LeftButton) &&
        (event->modifiers() == Qt::NoModifier))
    {
        emit pressed();
        // Just for testing: Toggle pixmap visibility
        _buttonImage->setVisible(!_buttonImage-isVisible());
        event->accept();
    }
    else
        QGraphicsWidget::mousePressEvent(event);
 
}
 
/* Tried my own implementation of boundingRect and shape,
   but it did not change anything
QRectF Button::boundingRect() const
{
    return QRectF(0,0,
                  _buttonImage->pixmap().width(),
                  _buttonImage->pixmap().height());
}
 
QPainterPath Button::shape() const
{
    if (_buttonImage)
        return _buttonImage->shape();
    else
    {
        QPainterPath emptyPath;
        return emptyPath;
    }
}
*/

#include "button.h"
#include <QGraphicsSceneMouseEvent>

Button::Button(QGraphicsItem *parent) :
    QGraphicsWidget(parent, 0)
{
    setSizePolicy(QSizePolicy::Fixed,
                  QSizePolicy::Fixed,
                  QSizePolicy::DefaultType);
    setPreferredSize(0,0);
    setAcceptHoverEvents(true);
}

void Button::setPixmap(const QPixmap pixmap)
{
    if (!_buttonImage)
        delete _buttonImage;

    _buttonImage = new QGraphicsPixmapItem(pixmap, this);
    _buttonImage->setPos(0,0);
    setPreferredSize(_buttonImage->pixmap().width(),
                     _buttonImage->pixmap().height());
}

void Button::mousePressEvent(QGraphicsSceneMouseEvent* event)
{
    if ((event->button() == Qt::LeftButton) &&
        (event->modifiers() == Qt::NoModifier))
    {
        emit pressed();
        // Just for testing: Toggle pixmap visibility
        _buttonImage->setVisible(!_buttonImage-isVisible());
        event->accept();
    }
    else
        QGraphicsWidget::mousePressEvent(event);

}

/* Tried my own implementation of boundingRect and shape,
   but it did not change anything
QRectF Button::boundingRect() const
{
    return QRectF(0,0,
                  _buttonImage->pixmap().width(),
                  _buttonImage->pixmap().height());
}

QPainterPath Button::shape() const
{
    if (_buttonImage)
        return _buttonImage->shape();
    else
    {
        QPainterPath emptyPath;
        return emptyPath;
    }
}
*/

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Thanks for any hints!

edit: typo

[Asperamanca]

I have since found out the problem only occurs if my Button object is a child of another QGraphicsWidget subclass (ButtonBar).
However, ButtonBar does not handle any events, or install any event filters. Why should a child of a QGraphicsWidget not receive any events?