How to draw rectangle over qwtPlotCurve?

[qmonkey]

Hi,

Is it possible to draw transparent colored resctangles over qwtPlotCurve(see attached example plot, red curve is the qwtPlotCurve) I'm thinking of drawing histogram and qwtPlotCurve on the same plot, but not sure if it is doable.

Anybody has a suggestion?

Thanks in advance!

[Uwe]

I'm thinking of drawing histogram and qwtPlotCurve on the same plot, but not sure if it is doable

In general you can have as many plot items as you want on a plot, but I recommend to implement a new plot item instead of misusing a histogram:

class RangeMarker: public QwtPlotItem
{
public:
    RangeMarker()    
    {
        setZ( ... );
    }
 
    void setInterval( QwtInterval& interval )
    {
        m_interval = interval;
    }
 
    virtual void draw( QPainter *painter,
        const QwtScaleMap &xMap, const QwtScaleMap &,
        const QRectF &canvasRect ) const
    {
        int x1 = qRound( xMap.transform( m_interval.minValue() ) );
        int x2 = qRound( xMap.transform( m_interval.maxValue() );
 
        painter->fillRect( QRect( x1, canvasRect.top(), x2 - x1, canvasRect.height() ), ... );
    }
};

class RangeMarker: public QwtPlotItem
{
public:
    RangeMarker()    
    {
        setZ( ... );
    }

    void setInterval( QwtInterval& interval )
    {
        m_interval = interval;
    }

    virtual void draw( QPainter *painter,
        const QwtScaleMap &xMap, const QwtScaleMap &,
        const QRectF &canvasRect ) const
    {
        int x1 = qRound( xMap.transform( m_interval.minValue() ) );
        int x2 = qRound( xMap.transform( m_interval.maxValue() );

        painter->fillRect( QRect( x1, canvasRect.top(), x2 - x1, canvasRect.height() ), ... );
    }
};

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HTH,
Uwe

[qmonkey]

Uwe,

This is exactly what I needed. I appreciated your time for replying with the code!