Getting mouse click location of a label in qt

Question

I googled around and found this forum thread in which the OP seems to have had the exact problem I am having. The question is, how would I inherit from QLabel and reimplement the mousepressed event? I'm guessing it would be something like this:

class CustomLabel : public QLabel
{
public:
    //what about the constructors?
    void mousePressEvent ( QMouseEvent * ev );
}

void CustomLabel::mousePressEvent ( QMouseEvent * ev )
{
    QPoint = ev->pos();
    //I want to have another function get the event position.
    //How would I achieve this? It's void!
    //Is there perhaps some way to set up a signal and slot with the position?
}

And after I have successfully created a CustomLabel class, how would I be able to put it in design view?

Answer 1

just like this :D

void CustomLabel::mousePressEvent(QMouseEvent *ev) 
{
QString x = QString::number(ev->x());
QString y = QString::number(ev->y());
qDebug() << x << "," << y;
}

Answer 2

Yes, you can set up a signal on your CustomLabel class and have your overridden version of mousePressEvent emit it. i.e.

class CustomLabel : public QLabel
{
Q_OBJECT
signals:
    void mousePressed( const QPoint& );

public:
    CustomLabel( QWidget* parent = 0, Qt::WindowFlags f = 0 );
    CustomLabel( const QString& text, QWidget* parent = 0, Qt::WindowFlags f = 0 );

    void mousePressEvent( QMouseEvent* ev );
};

void CustomLabel::mousePressEvent( QMouseEvent* ev )
{
    const QPoint p = ev->pos();
    emit mousePressed( p );
}

CustomLabel::CustomLabel( QWidget * parent, Qt::WindowFlags f )
    : QLabel( parent, f ) {}

CustomLabel::CustomLabel( const QString& text, QWidget* parent, Qt::WindowFlags f )
    : QLabel( text, parent, f ) {}

The constructors just mimic those of the base QLabel and therefore simply pass their arguments straight on to the corresponding base constructors.

Answer 3

Is it just me, or doesn't QMouseEvent already give the information you need?

int QMouseEvent::x () const

Returns the x position of the mouse cursor, relative to the widget that received the event.

See also y() and pos().

int QMouseEvent::y () const

Returns the y position of the mouse cursor, relative to the widget that received the event.

See also x() and pos().

Ref: http://doc.qt.nokia.com/4.7.old/qmouseevent.html#x