spectrogram with fixed aspect ratio (1:1) and zooming/unzooming

[gavinmagnus]

Thread is really old, but here's my solution:

class MyPlotZoomer : public QwtPlotZoomer {
 
// ...
 
private:
    int zx;
    int zy;
 
protected:
    virtual void widgetMousePressEvent(QMouseEvent *me);
    virtual void move(const QPoint &p);
};
 
void MyPlotZoomer::widgetMousePressEvent(QMouseEvent *me)
{
    if ( mouseMatch( MouseSelect1, me ) )
    {
        zx = me->pos().x();
        zy = me->pos().y();
    }
 
    QwtPlotPicker::widgetMousePressEvent(me);
}
 
void MyPlotZoomer::move(const QPoint &p)
{
    QPoint square;
 
    if( abs( p.x() - zx )
            >
        abs( p.y() - zy ) )
    {
        square.setX( p.x() );
 
        if( p.y() > zy )
            square.setY( zy + abs( p.x() - zx ) );
        else
            square.setY( zy - abs( p.x() - zx ) );
    }
    else
    {
        square.setY( p.y() );
 
        if( p.x() > zx )
            square.setX( zx + abs( p.y() - zy ) );
        else
            square.setX( zx - abs( p.y() - zy ) );
    }
 
    QwtPlotZoomer::move( square );
}

class MyPlotZoomer : public QwtPlotZoomer {

// ...
    
private:
    int zx;
    int zy;

protected:
    virtual void widgetMousePressEvent(QMouseEvent *me);
    virtual void move(const QPoint &p);
};

void MyPlotZoomer::widgetMousePressEvent(QMouseEvent *me)
{
    if ( mouseMatch( MouseSelect1, me ) )
    {
        zx = me->pos().x();
        zy = me->pos().y();
    }

    QwtPlotPicker::widgetMousePressEvent(me);
}

void MyPlotZoomer::move(const QPoint &p)
{
    QPoint square;

    if( abs( p.x() - zx )
            >
        abs( p.y() - zy ) )
    {
        square.setX( p.x() );

        if( p.y() > zy )
            square.setY( zy + abs( p.x() - zx ) );
        else
            square.setY( zy - abs( p.x() - zx ) );
    }
    else
    {
        square.setY( p.y() );

        if( p.x() > zx )
            square.setX( zx + abs( p.y() - zy ) );
        else
            square.setX( zx - abs( p.y() - zy ) );
    }

    QwtPlotZoomer::move( square );
}

To copy to clipboard, switch view to plain text mode 

[gavinmagnus]

Ok, this is bad, I cannot edit my incorrect post. It looks like all you need to do in QWT 6.3 is to overload QwtPlotZoomer::zoom and make it call QwtPlotRescaller::rescale()

class MyPlotZoomer : public QwtPlotZoomer 
{
public:
    MyPlotZoomer(QwtPlotCanvas* widget, bool doReplot=true);
    QwtPlotRescaler * myPlotRescaler;
 
    virtual void zoom(const QRectF& rect);
}
 
MyPlotZoomer::MyPlotZoomer(QwtPlotCanvas* widget, bool doReplot) :
    QwtPlotZoomer(widget, doReplot)
{
    myPlotRescaler = new QwtPlotRescaler( widget );
    //For example:
        myPlotRescaler->setRescalePolicy( QwtPlotRescaler::Expanding );
        myPlotRescaler->setExpandingDirection( QwtPlotRescaler::ExpandBoth );
        myPlotRescaler->setReferenceAxis(QwtPlot::xBottom);
        myPlotRescaler->setAspectRatio(QwtPlot::yLeft, 1.0);
        myPlotRescaler->setAspectRatio(QwtPlot::yRight, 0.0);
        myPlotRescaler->setAspectRatio(QwtPlot::xTop, 0.0);
}
 
MyPlotZoomer::zoom(const QRectF& rect)
{    
    QwtPlotZoomer::zoom(rect);
 
    //Most important
    myPlotRescaler->rescale();    
}

class MyPlotZoomer : public QwtPlotZoomer 
{
public:
    MyPlotZoomer(QwtPlotCanvas* widget, bool doReplot=true);
    QwtPlotRescaler * myPlotRescaler;

    virtual void zoom(const QRectF& rect);
}

MyPlotZoomer::MyPlotZoomer(QwtPlotCanvas* widget, bool doReplot) :
    QwtPlotZoomer(widget, doReplot)
{
    myPlotRescaler = new QwtPlotRescaler( widget );
    //For example:
        myPlotRescaler->setRescalePolicy( QwtPlotRescaler::Expanding );
        myPlotRescaler->setExpandingDirection( QwtPlotRescaler::ExpandBoth );
        myPlotRescaler->setReferenceAxis(QwtPlot::xBottom);
        myPlotRescaler->setAspectRatio(QwtPlot::yLeft, 1.0);
        myPlotRescaler->setAspectRatio(QwtPlot::yRight, 0.0);
        myPlotRescaler->setAspectRatio(QwtPlot::xTop, 0.0);
}

MyPlotZoomer::zoom(const QRectF& rect)
{    
    QwtPlotZoomer::zoom(rect);

    //Most important
    myPlotRescaler->rescale();    
}

To copy to clipboard, switch view to plain text mode