Inter-Line Coloring

The following is the command line version of the code in "cppdemo/linefill". 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 line chart
    double data0[] = {70, 73, 80, 90, 95, 93, 82, 77, 82, 101, 111, 115};
    const int data0_size = (int)(sizeof(data0)/sizeof(*data0));
    double data1[] = {90, 96, 89, 77, 82, 96, 109, 109, 99, 108, 96, 91};
    const int data1_size = (int)(sizeof(data1)/sizeof(*data1));
    double data2[] = {58, 34, 25, 49, 64, 10, 16, 40, 25, 49, 40, 22};
    const int data2_size = (int)(sizeof(data2)/sizeof(*data2));

    // The labels for the line chart
    const char* labels[] = {"2008-01", "2008-02", "2008-03", "2008-04", "2008-05", "2008-06",
        "2008-07", "2008-08", "2008-09", "2008-10", "2008-11", "2008-12"};
    const int labels_size = (int)(sizeof(labels)/sizeof(*labels));

    // Create a XYChart object of size 450 x 450 pixels
    XYChart* c = new XYChart(450, 450);

    // Add a title to the chart using 15pt Arial Italic font.
    TextBox* title = c->addTitle("Inter-line Coloring", "Arial Italic", 15);

    // Add a legend box where the top-center is anchored to the horizontal center of the chart, just
    // under the title. Use horizontal layout and 10 points Arial Bold font, and transparent
    // background and border. Use line style legend key.
    LegendBox* legendBox = c->addLegend(c->getWidth() / 2, title->getHeight(), false,
        "Arial Bold Italic", 10);
    legendBox->setBackground(Chart::Transparent, Chart::Transparent);
    legendBox->setAlignment(Chart::TopCenter);
    legendBox->setLineStyleKey();

    // Tentatively set the plotarea at (70, 65) and of (chart_width - 100) x (chart_height - 110) in
    // size. Use light grey (c0c0c0) border and horizontal and vertical grid lines.
    PlotArea* plotArea = c->setPlotArea(70, 65, c->getWidth() - 100, c->getHeight() - 110, -1, -1,
        0xc0c0c0, 0xc0c0c0, -1);

    // Add a title to the y axis using 12pt Arial Bold Italic font
    c->yAxis()->setTitle("Axis Title Placeholder", "Arial Bold Italic", 12);

    // Add a title to the x axis using 12pt Arial Bold Italic font
    c->xAxis()->setTitle("Axis Title Placeholder", "Arial Bold Italic", 12);

    // Set the axes line width to 3 pixels
    c->xAxis()->setWidth(3);
    c->yAxis()->setWidth(3);

    // Set the labels on the x axis.
    c->xAxis()->setLabels(StringArray(labels, labels_size));

    // Use 8 points Arial rotated by 90 degrees as the x-axis label font
    c->xAxis()->setLabelStyle("Arial", 8, Chart::TextColor, 90);

    // Add a spline curve to the chart
    SplineLayer* layer0 = c->addSplineLayer(DoubleArray(data0, data0_size), 0xff0000, "Data Set 0");
    layer0->setLineWidth(2);

    // Add a normal line to the chart
    LineLayer* layer1 = c->addLineLayer(DoubleArray(data1, data1_size), 0x008800, "Data Set 1");
    layer1->setLineWidth(2);

    // Color the region between the above spline curve and normal line. Use the semi-transparent red
    // (80ff000000) if the spline curve is higher than the normal line, otherwise use
    // semi-transparent green (80008800)
    c->addInterLineLayer(layer0->getLine(), layer1->getLine(), 0x80ff0000, 0x80008800);

    // Add another normal line to the chart
    LineLayer* layer2 = c->addLineLayer(DoubleArray(data2, data2_size), 0x0000ff, "Data Set 2");
    layer2->setLineWidth(2);

    // Add a horizontal mark line to the chart at y = 40
    Mark* mark = c->yAxis()->addMark(40, -1, "Threshold");
    mark->setLineWidth(2);

    // Set the mark line to purple (880088) dash line. Use white (ffffff) for the mark label.
    mark->setMarkColor(c->dashLineColor(0x880088), 0xffffff);

    // Put the mark label at the left side of the mark, with a purple (880088) background.
    mark->setAlignment(Chart::Left);
    mark->setBackground(0x880088);

    // Color the region between the above normal line and mark line. Use the semi-transparent blue
    // (800000ff) if the normal line is higher than the mark line, otherwise use semi-transparent
    // purple (80880088)
    c->addInterLineLayer(layer2->getLine(), mark->getLine(), 0x800000ff, 0x80880088);

    // Layout the legend box, so we can get its height
    c->layoutLegend();

    // Adjust the plot area size, such that the bounding box (inclusive of axes) is 10 pixels from
    // the left edge, just under the legend box, 25 pixels from the right edge, and 10 pixels from
    // the bottom edge.
    c->packPlotArea(10, legendBox->getTopY() + legendBox->getHeight(), c->getWidth() - 25,
        c->getHeight() - 10);

    // After determining the exact plot area position, we may adjust the legend box and the title
    // positions so that they are centered relative to the plot area (instead of the chart)
    legendBox->setPos(plotArea->getLeftX() + (plotArea->getWidth() - legendBox->getWidth()) / 2,
        legendBox->getTopY());
    title->setPos(plotArea->getLeftX() + (plotArea->getWidth() - title->getWidth()) / 2,
        title->getTopY());

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

    //free up resources
    delete c;

    return 0;
}