ChartDirector 6.0 (C++ Edition)

Track Box with Floating Legend (QT)

NOTE: This section describes Track Box with Floating Legend for QT only. For MFC, please refer to Track Box with Floating Legend (MFC).

This sample program demonstrates a track cursor programmed with the following features:

The code first draws the chart. Then in the QChartViewer.mouseMovePlotArea signal handler, the track cursor is drawn to reflect the mouse position. The track cursor is configured to automatically hide itself when the mouse leaves the plot area.

The trackBoxLegend method is the routine that draws the track cursor. Its key elements are:

Source Code Listing

The following is the main source code of this demo. The complete QT project is in "qtdemo/trackbox".

[File: qtdemo/trackbox/trackbox.cpp]
#include <QApplication>
#include "trackbox.h"
#include <vector>
#include <sstream>
#include <algorithm>

using namespace std;

int main(int argc, char *argv[])
    QApplication app(argc, argv);
    app.setStyleSheet("* {font-family:arial;font-size:11px}");
    TrackBox demo;;
    return app.exec();

TrackBox::TrackBox(QWidget *parent) :
    setWindowTitle("Track Box with Legend");

    // Create the QChartViewer and draw the chart
    m_ChartViewer = new QChartViewer(this);

    // Set the window to be of the same size as the chart
    setFixedSize(m_ChartViewer->width(), m_ChartViewer->height());

    // Set up the mouseMovePlotArea handler for drawing the track cursor
    connect(m_ChartViewer, SIGNAL(mouseMovePlotArea(QMouseEvent*)),

    delete m_ChartViewer->getChart();

// Draw the chart and display it in the given viewer
void TrackBox::drawChart(QChartViewer *viewer)
    // The data for the bar chart
    double data0[] = {100, 125, 245, 147, 67};
    double data1[] = {85, 156, 179, 211, 123};
    double data2[] = {97, 87, 56, 267, 157};
    const char *labels[] = {"Mon", "Tue", "Wed", "Thur", "Fri"};
    int noOfPoints = (int)(sizeof(data0)/sizeof(*data0));

    // Create a XYChart object of size 540 x 375 pixels
    XYChart *c = new XYChart(540, 375);

    // Add a title to the chart using 18 pts Times Bold Italic font
    c->addTitle("Average Weekly Network Load", "timesbi.ttf", 18);

    // Set the plotarea at (50, 55) and of 440 x 280 pixels in size. Use a vertical gradient color
    // from light blue (f9f9ff) to blue (6666ff) as background. Set border and grid lines to white
    // (ffffff).
    c->setPlotArea(50, 55, 440, 280, c->linearGradientColor(0, 55, 0, 335, 0xf9f9ff, 0x6666ff), -1,
        0xffffff, 0xffffff);

    // Add a legend box at (50, 28) using horizontal layout. Use 10pts Arial Bold as font, with
    // transparent background.
    c->addLegend(50, 28, false, "arialbd.ttf", 10)->setBackground(Chart::Transparent);

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

    // Draw the ticks between label positions (instead of at label positions)

    // Set axis label style to 8pts Arial Bold
    c->xAxis()->setLabelStyle("arialbd.ttf", 8);
    c->yAxis()->setLabelStyle("arialbd.ttf", 8);

    // Set axis line width to 2 pixels

    // Add axis title
    c->yAxis()->setTitle("Throughput (MBytes Per Hour)");

    // Add a multi-bar layer with 3 data sets
    BarLayer *layer = c->addBarLayer(Chart::Side);
    layer->addDataSet(DoubleArray(data0, noOfPoints), 0xff0000, "Server #1");
    layer->addDataSet(DoubleArray(data1, noOfPoints), 0x00ff00, "Server #2");
    layer->addDataSet(DoubleArray(data2, noOfPoints), 0xff8800, "Server #3");

    // Set bar border to transparent. Use glass lighting effect with light direction from left.
    layer->setBorderColor(Chart::Transparent, Chart::glassEffect(Chart::NormalGlare, Chart::Left));

    // Configure the bars within a group to touch each others (no gap)
    layer->setBarGap(0.2, Chart::TouchBar);

    // Set the chart image to the QChartViewer

// Draw track cursor when mouse is moving over plotarea
void TrackBox::onMouseMovePlotArea(QMouseEvent *)
    trackBoxLegend((XYChart *)m_ChartViewer->getChart(), m_ChartViewer->getPlotAreaMouseX(),
    // Hide the track cursor when the mouse leaves the plot area

// Draw the track box with legend
void TrackBox::trackBoxLegend(XYChart *c, int mouseX, int mouseY)
   // Clear the current dynamic layer and get the DrawArea object to draw on it.
    DrawArea *d = c->initDynamicLayer();

    // The plot area object
    PlotArea *plotArea = c->getPlotArea();

    // Get the data x-value that is nearest to the mouse
    double xValue = c->getNearestXValue(mouseX);

    // Compute the position of the box. This example assumes a label based x-axis, in which the
    // labeling spacing is one x-axis unit. So the left and right sides of the box is 0.5 unit from
    // the central x-value.
    int boxLeft = c->getXCoor(xValue - 0.5);
    int boxRight = c->getXCoor(xValue + 0.5);
    int boxTop = plotArea->getTopY();
    int boxBottom = plotArea->getBottomY();

    // Draw the track box
    d->rect(boxLeft, boxTop, boxRight, boxBottom, 0x000000, Chart::Transparent);

    // Container to hold the legend entries
    vector<string> legendEntries;

    // Iterate through all layers to build the legend array
    for(int i = 0; i < c->getLayerCount(); ++i) {
        Layer *layer = c->getLayerByZ(i);

        // The data array index of the x-value
        int xIndex = layer->getXIndexOf(xValue);

        // Iterate through all the data sets in the layer
        for(int j = 0; j < layer->getDataSetCount(); ++j) {
            DataSet *dataSet = layer->getDataSetByZ(j);

            // Build the legend entry, consist of the legend icon, the name and the data value.
            double dataValue = dataSet->getValue(xIndex);
            if ((dataValue != Chart::NoValue) && (dataSet->getDataColor() != (int)Chart::Transparent)) {
                ostringstream legendEntry;
                legendEntry << dataSet->getLegendIcon() << " " << dataSet->getDataName() << ": " 
                    << c->formatValue(dataValue, "{value|P4}");

    // Create the legend by joining the legend entries
    if (legendEntries.size() > 0) {
        ostringstream legend;
        legend << "<*block,bgColor=FFFFCC,edgeColor=000000,margin=5*><*font,underline=1*>" << 
            c->xAxis()->getFormattedLabel(xValue) << "<*/font*>";
        for (int i = ((int)legendEntries.size()) - 1; i >= 0; --i)
            legend << "<*br*>" << legendEntries[i];
        legend << "<*/*>";

        // Display the legend at the bottom-right side of the mouse cursor, and make sure the legend
        // will not go outside the chart image.
        TTFText *t = d->text(legend.str().c_str(), "arialbd.ttf", 8);
        t->draw(min(mouseX + 12, c->getWidth() - t->getWidth()), min(mouseY + 18, c->getHeight()
            - t->getHeight()), 0x000000, Chart::TopLeft);