Marks and Zones

This example demonstrates adding marks and zones to the chart, and adding custom legend keys to represent the zones.

A "mark" is a line drawn in the plot area. The purple "Alert" line and the green "Watch" line on the chart are mark lines. It is added to the chart using Axis.addMark.

Mark lines can be horizontal or vertical, depending on which axis the marks are defined on. Marks can be drawn on the front of the plot area (the default), or at the back like grid lines. This is configured using Mark.setDrawOnTop.

A "zone" is a color band on the back of the plot area. In this example, the red, yellow and green areas are zones. They are added to the chart using Axis.addZone. Like marks, zones can be horizontal or vertical.

In this example, LegendBox.addKey is used to add the names of the zones to the legend box as custom entries.

The following is the command line version of the code in "cppdemo/markzone". 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[] = {40, 45, 37, 24, 32, 39, 53, 52, 63, 49, 46, 40, 54, 50, 57, 57, 48, 49, 63, 67,
        74, 72, 70, 89, 74};
    const int data_size = (int)(sizeof(data)/sizeof(*data));
    const char* labels[] = {"0\nJun 4", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11",
        "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "0\nJun 5"};
    const int labels_size = (int)(sizeof(labels)/sizeof(*labels));

    // Create a XYChart object of size 400 x 270 pixels
    XYChart* c = new XYChart(400, 270);

    // Set the plotarea at (80, 60) and of size 300 x 200 pixels. Turn off the grid lines by setting
    // their colors to Transparent.
    c->setPlotArea(80, 28, 300, 200)->setGridColor(Chart::Transparent);

    // Add a title to the y axis
    TextBox* textbox = c->yAxis()->setTitle("Temperature");

    // Set the y axis title upright (font angle = 0)
    textbox->setFontAngle(0);

    // Put the y axis title on top of the axis
    textbox->setAlignment(Chart::TopLeft2);

    // Add green (0x99ff99), yellow (0xffff99) and red (0xff9999) zones to the y axis to represent
    // the ranges 0 - 50, 50 - 80, and 80 - max.
    c->yAxis()->addZone(0, 50, 0x99ff99);
    c->yAxis()->addZone(50, 80, 0xffff99);
    c->yAxis()->addZone(80, 9999, 0xff9999);

    // Add a purple (0x800080) mark at y = 70 using a line width of 2.
    c->yAxis()->addMark(70, 0x800080, "Alert = 70")->setLineWidth(2);

    // Add a green (0x008000) mark at y = 40 using a line width of 2.
    c->yAxis()->addMark(40, 0x008000, "Watch = 40")->setLineWidth(2);

    // Add a legend box at (165, 0) (top right of the chart) using 8pt Arial font. and horizontal
    // layout.
    LegendBox* legend = c->addLegend(165, 0, false, "Arial Bold", 8);

    // Disable the legend box boundary by setting the colors to Transparent
    legend->setBackground(Chart::Transparent, Chart::Transparent);

    // Add 3 custom entries to the legend box to represent the 3 zones
    legend->addKey("Normal", 0x80ff80);
    legend->addKey("Warning", 0xffff80);
    legend->addKey("Critical", 0xff8080);

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

    // Display 1 out of 3 labels on the x-axis. Show minor ticks for remaining labels.
    c->xAxis()->setLabelStep(3, 1);

    // Add a 3D bar layer with the given data
    BarLayer* layer = c->addBarLayer(DoubleArray(data, data_size), 0xbbbbff);

    // Set the bar gap to 0 so that the bars are packed tightly
    layer->setBarGap(0);

    // Set the border color of the bars same as the fill color, with 1 pixel 3D border effect.
    layer->setBorderColor(Chart::SameAsMainColor, 1);

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

    //free up resources
    delete c;

    return 0;
}