Custom plot selection

[gorec323]

Of course it is ( see QwtPickerRubberband::drawOverlay in qwt_picker.cpp ) - or where else do you believe gets your VLineRubberBand painted ?

Uwe

Sorry. It's my error.

class ChartZoomer : public QwtPlotZoomer
// not correct
// void drawRubberBand(QPainter *painter); // <-- it is my error!!!!
// correct
void drawRubberBand(QPainter *painter) const;
}

void drawRubberBand(QPainter *painter) const; <> void drawRubberBand(QPainter *painter);

[alketi]

I have a similar question to the OP, so I'll put it here rather than starting a new thread, just to keep it all in context.

How does one temporarily fill the rectangular rubberband area with a translucent color? (I want the fill visible only while the rubber band is being drawn.)

My attempt was to override QwtPicker and re-implement drawRubberBand(), however this code actually does nothing. And even commenting-out the parent call at the end still results in the rectangular zoom outline being drawn. So I'm confused. Any advice Uwe would be appreciated.

SETUP

m_picker = new XQwtPicker( QwtPicker::RectRubberBand,
                           QwtPicker::AlwaysOn, 
                           this->canvas() );
m_picker->setRubberBandPen( QColor( Qt::green ) );
m_picker->setRubberBand( QwtPicker::CrossRubberBand );
m_picker->setTrackerPen( QColor( Qt::white ) );

m_picker = new XQwtPicker( QwtPicker::RectRubberBand,
                           QwtPicker::AlwaysOn, 
                           this->canvas() );
m_picker->setRubberBandPen( QColor( Qt::green ) );
m_picker->setRubberBand( QwtPicker::CrossRubberBand );
m_picker->setTrackerPen( QColor( Qt::white ) );

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SUBCLASS

void XQwtPicker::drawRubberBand( QPainter *painter ) const
{
    const QPolygon pa = QwtPicker::selection();
    const QRect rect  = QRect( pa.first(), pa.last() ).normalized();
 
    QColor fillColor = QwtPicker::rubberBandPen().color();
    fillColor.setAlpha(125);
 
    QBrush fillBrush(fillColor);
 
    QwtPainter::fillRect( painter, rect, fillBrush );
 
    // QwtPicker::drawRubberBand(painter);
}

void XQwtPicker::drawRubberBand( QPainter *painter ) const
{
    const QPolygon pa = QwtPicker::selection();
    const QRect rect  = QRect( pa.first(), pa.last() ).normalized();

    QColor fillColor = QwtPicker::rubberBandPen().color();
    fillColor.setAlpha(125);

    QBrush fillBrush(fillColor);

    QwtPainter::fillRect( painter, rect, fillBrush );

    // QwtPicker::drawRubberBand(painter);
}

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[Uwe]

You also need to implement:

QRegion XQwtPicker::rubberBandMask() const override;

QRegion XQwtPicker::rubberBandMask() const override;

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The smaller the region the better - but beside of environments like remote X11 you probably won't notice much difference when returning the complete canvas rectangle.
In your case the optimal solution would be the rectangle spanned by the w points. See https://qwt.sourceforge.io/class_qwt...04f237062b75fc

Have a look at the implementation of QwtPicker::rubberBandMask - it will help with how to find the rectangle.

HTH,
Uwe