Zooming function on a QWidget

Question

I have a QWidget where I am drawing some lines and I would like to enable/implement a zooming function so as to better see the picture which I am drawing. And I want to conn

Answer 1

Try to reimplement your paintEvent , and apply scale to QPainter before drawing.

class YourClass:public QWidget
{
...
  protected:
     void paintEvent ( QPaintEvent * event );
     void wheelEvent ( QWheelEvent * event );
  private:
     qreal scale;
};

void YourClass::paintEvent ( QPaintEvent * event )
{
    QPainter p;
    p.scale(scale,scale);
// paint here
}
void YourClass::wheelEvent ( QWheelEvent * event )
{
    scale+=(event->delta()/120); //or use any other step for zooming 
}

Answer 2

I used this solution before and I have to say that is obsoleted in the las Qt versions. To create this function is all the same except " event->delta()", now it is written "event->angleDelta().y()"