Qwt Histogram Data Labels

[AlphaWolfXV]

Hello all,
Does anyone know of a nifty way to add data labels (i.e. the value of the bar) on a histogram plot. I have a simple histogram displaying correctly, but would really like to be able to show the value of the bar on top, similar to an excel chart.

I am running Windows Vista, Qt Creator 1.2.1 (Qt 4.5.2), Qwt5.2

Thanks for any help you can provide!
AlphaWolfXV

[amoswood]

Does anyone know of a nifty way to add data labels (i.e. the value of the bar) on a histogram plot. I have a simple histogram displaying correctly, but would really like to be able to show the value of the bar on top, similar to an excel chart.

You need to draw the text manually on top of your plot histogram. To do so, overlaod your HistPlot::drawCanvas function.

class HistPlot : public QwtPlot
{
  void drawCanvas(QPainter * painter)
  {
    // Let the original canvas draw itself.
    QwtPlot::drawCanvas(painter);
 
    // Now draw your text on top
  }
 
};

class HistPlot : public QwtPlot
{
  void drawCanvas(QPainter * painter)
  {
    // Let the original canvas draw itself.
    QwtPlot::drawCanvas(painter);

    // Now draw your text on top
  }
 
};

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[Uwe]

When you are using QwtPlotHistogram from trunk you could overload drawColumn. All you need to do is to add some layout code for the text rectangle and a painter->drawText() ( or better QwtPainter::drawText() if you want to print/export your plot ).

Uwe

[amoswood]

Yeah, that would probably be a better solution.