How to draw aligned elements next to QwtLegendItem

Hi.

I have the next problem. I need draw number next to text of legend's item.

This number is changeable and all numbers must be aligned in one column for each legend's item.

For example:

first legend item 23.00
second legend item 900.00
third legend item 3.00


I tried to implement the next solution. I subclassed QwtLegenItem and overrided function drawText. Then I was finding the legend's item with maximal width, converted its width in pixels with help QwtMetricsMap and used function drawText several times.

Code:

---

void XRealTimeLegendItem::drawText(QPainter *painter, const QRect &rect)
{
    QString currentValue = QString().setNum( currentItemValue->value() );
 
    QFontMetrics fontMetrics = painter->fontMetrics();
    const QwtMetricsMap &map = QwtPainter::metricsMap();
 
    int maxItemWidth = map.screenToLayoutX( fontMetrics.width( maxItemName ) );
 
    painter->drawText( rect, text().text() );
 
    QRect valueRect = rect;
    valueRect.setX( rect.right() - rect.width() + maxItemWidth + 2 * spacing() );
    painter->drawText( valueRect, currentValue );
}

---

But print of QwtPlot doesn't work for this solution. The result of print is

first legend item
second legend item
third legend item

without numbers!

How can I draw numbers aligned in one column with correct print ?

Did you reimplement QwtPlotCurve::legendItem() returning a XRealTimeLegendItem ?

Of course you also have to implement XRealTimeLegendItem::sizeHint() to add the extra pixels you need to draw your numbers.

But probably it's easier to use rich text for the alignment.

Uwe

Quote:

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Originally Posted by Uwe

Did you reimplement QwtPlotCurve::legendItem() returning a XRealTimeLegendItem ?

Of course you also have to implement XRealTimeLegendItem::sizeHint() to add the extra pixels you need to draw your numbers.

But probably it's easier to use rich text for the alignment.

Uwe

---

Yes, I reimplemented QwtPlotCurve::legendItem.

But your method with rich text is really easier.

I subclassed QwtPlotCurve and defined function updateLegendItem and used <table> tag in rich text.

Code:

---

void XRealTimeCurve::updateLegendItem()
{
    QString legendItemValue = QString().setNum( y( dataSize() - 1 ), 'f', 2 );
 
    QFontMetrics fontMetrics( QwtText().font() );
 
    int maxWidth =  fontMetrics.width( maxPenName ) + 10;
 
    QString table = "<table> <tr> <td width="+ QString().setNum( maxWidth ) + ">" + legendItemName + "</td> <td width=50>" +
                    legendItemValue + "</td> </tr> </table>";
 
    setTitle( QwtText( table, QwtText::RichText ) );
}

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Now it needn't subclass QwtLegendItem::drawText with complicated code. It works fine, thanks.

For updating the curve title updateLegendItem() is the wrong place !

Uwe

Yes, I moved the code from XRealTimeCurve and now I am saving legendItemName in XRealTimeCurve only.

Code:

---

class XRealTimeCurve : public QwtPlotCurve
{
public:
    void setLegendItemName( const QString& name );
 
    QString legendItemName() const;
private:
    QString legendItem;
}
 
void XTrendViewer::updateCurveTitle( XTrendCurve* curve )
{
    int dataSize = curve->dataSize();
    if ( dataSize == 0 )
    {
        curve->setTitle( curve->legendItemName() );
        return;
    }
 
    QPointF currentPoint = curve->sample( dataSize - 1 );
    QString legendItemValue = QString().setNum( currentPoint.y(), 'f', 2 );
 
    QFontMetrics fontMetrics( QwtText().font() );
 
    int maxWidth =  fontMetrics.width( maxPenName ) + 10;
 
    QString table = "<table> <tr> <td width="+ QString().setNum( maxWidth ) + ">" + curve->legendItemName() + "</td> <td width=50>" +
                    legendItemValue + "</td> </tr> </table>";
 
    curve->setTitle( QwtText( table, QwtText::RichText ) );
}

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I set title and legend item's text from external place in class XTrendViewer : public QwtPlot