Example (JKQTPlotter): Barchart With Custom Draw Functor

This project (see barchart_customdrawfunctor shows how to draw customized barcharts, with a custom draw functor.

The source code of the main application is (see barchart_customdrawfunctor.cpp:

// 1. create a plotter window and get a pointer to the internal datastore (for convenience)
JKQTPDatastore* ds=plot.getDatastore();
 
// 2. now we create two columns for key and value
size_t columnK=ds->addLinearColumn(7, 0, 6, "k");
size_t columnV=ds->addColumnCalculatedFromColumn(columnK, [](double x) { return jkqtp_sign(2.0*x-2.5)*qMax(2.0,fabs(2.0*x-2.5)); }, "v");
 
// 3. load a stylesheet
plot.loadCurrentPlotterStyle(QSettings(":/JKQTPlotter/styles/seaborn.ini", QSettings::IniFormat));
 
// 4. create graph in the plot, which plots the dataset:
JKQTPBarVerticalGraph* graph=new JKQTPBarVerticalGraph(&plot);
graph->setKeyColumn(columnK);
graph->setValueColumn(columnV);
// this is the custom draw functor
graph->setCustomDrawingFunctor(
[](JKQTPEnhancedPainter& painter, const QRectF& bar_px, const QPointF& datapoint, Qt::Orientation orientation, JKQTPBarGraphBase* graph) {
    painter.save();
    painter.setPen(Qt::NoPen);
    QBrush b=painter.brush();
    QBrush bDeco=b;
    bDeco.setColor(b.color().lighter());
    // we draw the bar with a rounded end and add a lightly colored circle near the top
    if (orientation==Qt::Vertical) {
        // for vertical barcharts
        const double dx=bar_px.width()/2.0;
        const double r=dx*0.85;
        // depending in whether the bar elongates above or below the baseline,
        // we have to align the circle wrt the top or the bottom of the rectangle bar_px
        if (datapoint.y()>=graph->getBaseline()) {
            painter.drawComplexRoundedRect(bar_px, dx, dx, 0, 0, Qt::AbsoluteSize);
            painter.setBrush(bDeco);
            painter.drawEllipse(QPointF(bar_px.center().x(), bar_px.top()+dx), r,r);
        } else {
            painter.drawComplexRoundedRect(bar_px, 0, 0, dx, dx, Qt::AbsoluteSize);
            painter.setBrush(bDeco);
            painter.drawEllipse(QPointF(bar_px.center().x(), bar_px.bottom()-dx), r,r);
        }
    } else {
        // for horizontal barcharts
        const double dx=bar_px.height()/2.0;
        const double r=dx*0.85;
        if (datapoint.x()>=graph->getBaseline()) {
            painter.drawComplexRoundedRect(bar_px, 0, dx, 0, dx, Qt::AbsoluteSize);
            painter.setBrush(bDeco);
            painter.drawEllipse(QPointF(bar_px.right()-dx, bar_px.center().y()), r,r);
        } else {
            painter.drawComplexRoundedRect(bar_px, dx,0,dx,0, Qt::AbsoluteSize);
            painter.setBrush(bDeco);
            painter.drawEllipse(QPointF(bar_px.left()+dx, bar_px.center().y()), r,r);
        }
    }
    painter.restore();
}
);
// enable usage of cutom draw functor
graph->setUseCustomDrawFunctor(true);
// set graph color
graph->setColor(QColor("blue"));
plot.addGraph(graph);
 
 
// 5. autoscale the plot so the graph is contained
plot.zoomToFit();
 
// 6. show plotter and make it a decent size
plot.setWindowTitle(title);
plot.show();
plot.resize(400,400);

The result looks like this:

In order to draw horizontal error bars, you have to use JKQTPBarHorizontalGraph instead of JKQTPBarVerticalGraph. The functor given above also covers that case by checking the parameter orientation: