Multi-Color Line Chart

The following is the command line version of the code in "cppdemo/multicolorline". 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[])
{
    // Data points for the line chart
    double dataX[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
        22, 23, 24, 25};
    const int dataX_size = (int)(sizeof(dataX)/sizeof(*dataX));
    double dataY[] = {30, 28, 40, 55, 75, 68, 54, 60, 50, 62, 75, 65, 75, 89, 60, 55, 53, 35, 50,
        66, 56, 48, 52, 65, 62, 70};
    const int dataY_size = (int)(sizeof(dataY)/sizeof(*dataY));

    // The data point type. The color of the line segment will be based on the starting point type
    // of the segment. In this example, we have 4 point types for 4 different colors. Note that for
    // a line with N points, there will be (N - 1) line segments, so we only need (N - 1) values in
    // the point type array.
    int pointType[] = {0, 0, 0, 1, 1, 0, 2, 3, 1, 1, 0, 0, 1, 1, 2, 2, 2, 3, 3, 2, 0, 1, 2, 3, 3};
    const int pointType_size = (int)(sizeof(pointType)/sizeof(*pointType));
    int colors[] = {0xff0000, 0x0066ff, 0xcc00cc, 0x00cc00};
    const int colors_size = (int)(sizeof(colors)/sizeof(*colors));
    const char* pointTypeLabels[] = {"Alpha", "Beta", "Gamma", "Delta"};
    const int pointTypeLabels_size = (int)(sizeof(pointTypeLabels)/sizeof(*pointTypeLabels));

    // Create a XYChart object of size 600 x 430 pixels
    XYChart* c = new XYChart(600, 430);

    // Set default text color to dark grey (0x333333)
    c->setColor(Chart::TextColor, 0x333333);

    // Add a title box using grey (0x555555) 20pt Arial font
    c->addTitle("    Multi-Color Line Chart", "Arial", 20, 0x555555);

    // Set the plotarea at (70, 70) and of size 500 x 300 pixels, with transparent background and
    // border and light grey (0xcccccc) horizontal grid lines
    c->setPlotArea(70, 70, 500, 300, Chart::Transparent, -1, Chart::Transparent, 0xcccccc);

    // Add a legend box with horizontal layout above the plot area at (70, 35). Use 12pt Arial font,
    // transparent background and border, and line style legend icon.
    LegendBox* b = c->addLegend(70, 35, false, "Arial", 12);
    b->setBackground(Chart::Transparent, Chart::Transparent);
    b->setLineStyleKey();

    // Set axis label font to 12pt Arial
    c->xAxis()->setLabelStyle("Arial", 12);
    c->yAxis()->setLabelStyle("Arial", 12);

    // Set the x and y axis stems to transparent, and the x-axis tick color to grey (0xaaaaaa)
    c->xAxis()->setColors(Chart::Transparent, Chart::TextColor, Chart::TextColor, 0xaaaaaa);
    c->yAxis()->setColors(Chart::Transparent);

    // Set the major/minor tick lengths for the x-axis to 10 and 0.
    c->xAxis()->setTickLength(10, 0);

    // For the automatic axis labels, set the minimum spacing to 80/40 pixels for the x/y axis.
    c->xAxis()->setTickDensity(80);
    c->yAxis()->setTickDensity(40);

    // Add a title to the y axis using dark grey (0x555555) 14pt Arial font
    c->xAxis()->setTitle("X-Axis Title Placeholder", "Arial", 14, 0x555555);
    c->yAxis()->setTitle("Y-Axis Title Placeholder", "Arial", 14, 0x555555);

    // In ChartDirector, each line layer can only have one line color, so we use 4 line layers to
    // draw the 4 different colors of line segments.

    // In general, the line segments for each color will not be continuous. In ChartDirector,
    // non-continuous line segments can be achieved by inserting NoValue points. To allow for these
    // extra points, we use a buffer twice the size of the original data arrays.
    const int lineX_size = dataX_size * 2;
    double lineX[lineX_size];
    const int lineY_size = dataY_size * 2;
    double lineY[lineY_size];

    // Use a loop to create a line layer for each color
    for(int i = 0; i < colors_size; ++i) {
        int n = 0;
        for(int j = 0; j < dataX_size; ++j) {
            // We include data points of the target type in the line layer.
            if ((j < pointType_size) && (pointType[j] == i)) {
                lineX[n] = dataX[j];
                lineY[n] = dataY[j];
                n = n + 1;
            } else if ((j > 0) && (pointType[j - 1] == i)) {
                // If the current point is not of the target, but the previous point is of the
                // target type, we still need to include the current point in the line layer, as it
                // takes two points to draw a line segment. We also need an extra NoValue point so
                // that the current point will not join with the next point.
                lineX[n] = dataX[j];
                lineY[n] = dataY[j];
                n = n + 1;
                lineX[n] = dataX[j];
                lineY[n] = Chart::NoValue;
                n = n + 1;
            }
        }
        // Draw the layer that contains all segments of the target color
        LineLayer* layer = c->addLineLayer(DoubleArray(lineY, n), colors[i], pointTypeLabels[i]);
        layer->setXData(DoubleArray(lineX, n));
        layer->setLineWidth(2);
    }

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

    //free up resources
    delete c;

    return 0;
}