ChartDirector 6.0 (C++ Edition)

Track Line with Data Labels (QT)




NOTE: This section describes Track Line with Data Labels for QT only. For MFC, please refer to Track Line with Data Labels (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 trackLineLabel 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/tracklabel".

[File: qtdemo/tracklabel/tracklabel.cpp]
#include <QApplication>
#include "tracklabel.h"
#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}");
    TrackLabel demo;
    demo.show();
    return app.exec();
}


TrackLabel::TrackLabel(QWidget *parent) :
    QDialog(parent)
{
    setWindowTitle("Track Line with Data Labels");

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

    // 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*)),
        SLOT(onMouseMovePlotArea(QMouseEvent*)));
}

TrackLabel::~TrackLabel()
{
    delete m_ChartViewer->getChart();
}

//
// Draw the chart and display it in the given viewer
//
void TrackLabel::drawChart(QChartViewer *viewer)
{
    // Data for the chart as 3 random data series
    RanSeries r(127);
    DoubleArray data0 = r.getSeries(100, 100, -15, 15);
    DoubleArray data1 = r.getSeries(100, 150, -15, 15);
    DoubleArray data2 = r.getSeries(100, 200, -15, 15);
    DoubleArray timeStamps = r.getDateSeries(100, Chart::chartTime(2011, 1, 1), 86400);

    // Create a XYChart object of size 640 x 400 pixels
    XYChart *c = new XYChart(640, 400);

    // Add a title to the chart using 18 pts Times New Roman Bold Italic font
    c->addTitle("    Product Line Global Revenue", "timesbi.ttf", 18);

    // Set the plotarea at (50, 55) with width 70 pixels less than chart width, and height 90 pixels
    // less than chart height. Use a vertical gradient from light blue (f0f6ff) to sky blue (a0c0ff)
    // as background. Set border to transparent and grid lines to white (ffffff).
    c->setPlotArea(50, 55, c->getWidth() - 70, c->getHeight() - 90, c->linearGradientColor(0, 55, 0,
        c->getHeight() - 35, 0xf0f6ff, 0xa0c0ff), -1, Chart::Transparent, 0xffffff, 0xffffff);

    // Add a legend box at (50, 25) using horizontal layout. Use 10pts Arial Bold as font. Set the
    // background and border color to Transparent.
    c->addLegend(50, 25, false, "arialbd.ttf", 10)->setBackground(Chart::Transparent);

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

    // Set the axis stem to transparent
    c->xAxis()->setColors(Chart::Transparent);
    c->yAxis()->setColors(Chart::Transparent);

    // Configure x-axis label format
    c->xAxis()->setMultiFormat(Chart::StartOfYearFilter(), "{value|mm/yyyy} ",
        Chart::StartOfMonthFilter(), "{value|mm}");

    // Add axis title using 10pts Arial Bold Italic font
    c->yAxis()->setTitle("USD millions", "arialbi.ttf", 10);

    // Add a line layer to the chart using a line width of 2 pixels.
    LineLayer *layer = c->addLineLayer();
    layer->setLineWidth(2);

    // Add 3 data series to the line layer
    layer->setXData(timeStamps);
    layer->addDataSet(data0, 0xff3333, "Alpha");
    layer->addDataSet(data1, 0x008800, "Beta");
    layer->addDataSet(data2, 0x3333cc, "Gamma");

    // Set the chart image to the QChartViewer
    viewer->setChart(c);
}

//
// Draw track cursor when mouse is moving over plotarea
//
void TrackLabel::onMouseMovePlotArea(QMouseEvent *)
{
    trackLineLabel((XYChart *)m_ChartViewer->getChart(), m_ChartViewer->getPlotAreaMouseX());
    m_ChartViewer->updateDisplay();
    
    // Hide the track cursor when the mouse leaves the plot area
    m_ChartViewer->removeDynamicLayer("mouseLeavePlotArea");
}

//
// Draw track line with data labels
//
void TrackLabel::trackLineLabel(XYChart *c, int mouseX)
{
    // 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, and find its pixel coordinate.
    double xValue = c->getNearestXValue(mouseX);
    int xCoor = c->getXCoor(xValue);

    // Draw a vertical track line at the x-position
    d->vline(plotArea->getTopY(), plotArea->getBottomY(), xCoor,
        d->dashLineColor(0x000000, 0x0101));

    // Draw a label on the x-axis to show the track line position.
    ostringstream xlabel;
    xlabel << "<*font,bgColor=000000*> " << c->xAxis()->getFormattedLabel(xValue, "mmm dd, yyyy")
        << " <*/font*>";
    TTFText *t = d->text(xlabel.str().c_str(), "arialbd.ttf", 8);

    // Restrict the x-pixel position of the label to make sure it stays inside the chart image.
    int xLabelPos = max(0, min(xCoor - t->getWidth() / 2, c->getWidth() - t->getWidth()));
    t->draw(xLabelPos, plotArea->getBottomY() + 6, 0xffffff);
    t->destroy();

    // Iterate through all layers to draw the data labels
    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);
            const char *dataSetName = dataSet->getDataName();

            // Get the color, name and position of the data label
            int color = dataSet->getDataColor();
            int yCoor = c->getYCoor(dataSet->getPosition(xIndex), dataSet->getUseYAxis());

            // Draw a track dot with a label next to it for visible data points in the plot area
            if ((yCoor >= plotArea->getTopY()) && (yCoor <= plotArea->getBottomY()) && (color !=
                (int)Chart::Transparent) && dataSetName && *dataSetName)
            {
                d->circle(xCoor, yCoor, 4, 4, color, color);

                ostringstream label;
                label << "<*font,bgColor=" << hex << color << "*> "
                    << c->formatValue(dataSet->getValue(xIndex), "{value|P4}") << " <*font*>";
                t = d->text(label.str().c_str(), "arialbd.ttf", 8);

                // Draw the label on the right side of the dot if the mouse is on the left side the
                // chart, and vice versa. This ensures the label will not go outside the chart image.
                if (xCoor <= (plotArea->getLeftX() + plotArea->getRightX()) / 2)
                    t->draw(xCoor + 5, yCoor, 0xffffff, Chart::Left);
                else
                    t->draw(xCoor - 5, yCoor, 0xffffff, Chart::Right);

                t->destroy();
            }
        }
    }
}