Variable Width Bar Chart

The following is the command line version of the code in "cppdemo/varwidthbar". The MFC version of the code is in "mfcdemo/mfcdemo". The Qt Widgets version of the code is in "qtdemo/qtdemo". The QML/Qt Quick version of the code is in "qmldemo/qmldemo".
#include "chartdir.h"

int main(int argc, char *argv[])
{
    // The data for the chart
    double data[] = {800, 600, 1000, 1400};
    const int data_size = (int)(sizeof(data)/sizeof(*data));
    double widths[] = {250, 500, 960, 460};
    const int widths_size = (int)(sizeof(widths)/sizeof(*widths));
    const char* labels[] = {"Wind", "Hydro", "Coal", "Natural Gas"};
    const int labels_size = (int)(sizeof(labels)/sizeof(*labels));

    // The colors to use
    int colors[] = {0x00aa00, 0x66aaee, 0xee6622, 0xffbb00};
    const int colors_size = (int)(sizeof(colors)/sizeof(*colors));

    // Create a XYChart object of size 500 x 350 pixels
    XYChart* c = new XYChart(500, 350);

    // Add a title to the chart using 15pt Arial Italic font
    c->addTitle("Energy Generation Breakdown", "Arial Italic", 15);

    // Set the plotarea at (60, 60) and of (chart_width - 90) x (chart_height - 100) in size. Use a
    // vertical gradient color from light blue (f9f9ff) to sky blue (aaccff) as background. Set grid
    // lines to white (ffffff).
    int plotAreaBgColor = c->linearGradientColor(0, 60, 0, c->getHeight() - 40, 0xaaccff, 0xf9fcff);
    c->setPlotArea(60, 60, c->getWidth() - 90, c->getHeight() - 100, plotAreaBgColor, -1, -1,
        0xffffff);

    // Add a legend box at (50, 30) using horizontal layout and transparent background.
    c->addLegend(55, 30, false)->setBackground(Chart::Transparent);

    // Add titles to x/y axes with 10 points Arial Bold font
    c->xAxis()->setTitle("Mega Watts", "Arial Bold", 10);
    c->yAxis()->setTitle("Cost per MWh (dollars)", "Arial Bold", 10);

    // Set the x axis rounding to false, so that the x-axis will fit the data exactly
    c->xAxis()->setRounding(false, false);

    // In ChartDirector, there is no bar layer that can have variable bar widths, but you may create
    // a bar using an area layer. (A bar can be considered as the area under a rectangular outline.)
    // So by using a loop to create one bar per area layer, we can achieve a variable width bar
    // chart.

    // starting position of current bar
    double currentX = 0;

    for(int i = 0; i < data_size; ++i) {
        // ending position of current bar
        double nextX = currentX + widths[i];

        // outline of the bar
        double dataX[] = {currentX, currentX, nextX, nextX};
        const int dataX_size = (int)(sizeof(dataX)/sizeof(*dataX));
        double dataY[] = {0, data[i], data[i], 0};
        const int dataY_size = (int)(sizeof(dataY)/sizeof(*dataY));

        // create the area layer to fill the bar
        AreaLayer* layer = c->addAreaLayer(DoubleArray(dataY, dataY_size), colors[i], labels[i]);
        layer->setXData(DoubleArray(dataX, dataX_size));

        // the ending position becomes the starting position of the next bar
        currentX = nextX;
    }

    // Output the chart
    c->makeChart("varwidthbar.png");

    //free up resources
    delete c;

    return 0;
}