ChartDirector 6.1 (Java Edition)

Track Line with Legend (Web)

NOTE: This section describes Track Line with Legend for web applications only. For Windows applications, please refer to Track Line with Legend (Windows).

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

On the server side, the code draws the chart as usual, and outputs both the image and the Javascript Chart Model of the chart.

On the browser side, in the window onload event handler, Javascript is used to set up the event handler for the MouseMovePlotArea, TouchStartPlotArea, TouchMovePlotArea , ChartMove and Now events. The event handler calls trackLineLegend to draw the track cursor.

The trackLineLegend Javascript function is the routine that draws the track cursor. Its key elements are:

Source Code Listing

[JSP Version] jspdemo/tracklegend.jsp
<%@page import="ChartDirector.*" %>
<%@page import="java.util.*" %>
// Data for the chart as 3 random data series
RanSeries r = new RanSeries(127);
double[] data0 = r.getSeries(100, 100, -15, 15);
double[] data1 = r.getSeries(100, 150, -15, 15);
double[] data2 = r.getSeries(100, 200, -15, 15);
Date[] timeStamps = r.getDateSeries(100, new GregorianCalendar(2011, 0, 1).getTime(), 86400);

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

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

// Set axis label style to 8pt Arial Bold
c.xAxis().setLabelStyle("Arial Bold", 8);
c.yAxis().setLabelStyle("Arial Bold", 8);

// Set the axis stem to transparent

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

// Add axis title using 10pt Arial Bold Italic font
c.yAxis().setTitle("USD millions", "Arial Bold Italic", 10);

// Add a line layer to the chart using a line width of 2 pixels.
LineLayer layer = c.addLineLayer2();

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

// Create the WebChartViewer object
WebChartViewer viewer = new WebChartViewer(request, "chart1");

// Output the chart
String chartQuery = c.makeSession(viewer.getRequest(), viewer.getId());

// Set the chart URL to the viewer
viewer.setImageUrl("getchart.jsp?" + chartQuery);

// Output Javascript chart model to the browser to support tracking cursor

<!DOCTYPE html>
    <title>Track Line with Legend</title>
    <script type="text/javascript" src="cdjcv.js"></script>
<body style="margin:5px 0px 0px 5px">
<script type="text/javascript">

// Use the window load event to set up the MouseMovePlotArea event handler
JsChartViewer.addEventListener(window, 'load', function() {
    var viewer = JsChartViewer.get('<%=viewer.getId()%>');

    // Draw track cursor when mouse is moving over plotarea
    viewer.attachHandler(["MouseMovePlotArea", "TouchStartPlotArea", "TouchMovePlotArea", "ChartMove", "Now"],
    function(e) {
        this.preventDefault(e);   // Prevent the browser from using touch events for other actions
        trackLineLegend(viewer, viewer.getPlotAreaMouseX());

// Draw track line with legend
function trackLineLegend(viewer, mouseX)
    // Remove all previously drawn tracking object

    // The chart and its plot area
    var c = viewer.getChart();
    var plotArea = c.getPlotArea();

    // Get the data x-value that is nearest to the mouse, and find its pixel coordinate.
    var xValue = c.getNearestXValue(mouseX);
    var xCoor = c.getXCoor(xValue);
    if (xCoor == null)

    // Draw a vertical track line at the x-position
    viewer.drawVLine("trackLine", xCoor, plotArea.getTopY(), plotArea.getBottomY(), "black 1px dotted");

    // Array to hold the legend entries
    var legendEntries = [];

    // Iterate through all layers to build the legend array
    for (var i = 0; i < c.getLayerCount(); ++i)
        var layer = c.getLayerByZ(i);

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

        // Iterate through all the data sets in the layer
        for (var j = 0; j < layer.getDataSetCount(); ++j)
            var dataSet = layer.getDataSetByZ(j);

            // We are only interested in visible data sets with names, as they are required for legend entries.
            var dataName = dataSet.getDataName();
            var color = dataSet.getDataColor();
            if ((!dataName) || (color == null))

            // Build the legend entry, consist of a colored square box, the name and the data value.
            var dataValue = dataSet.getValue(xIndex);
            legendEntries.push("<nobr>" + viewer.htmlRect(7, 7, color) + " " + dataName + ": " +
                ((dataValue == null) ? "N/A" : dataValue.toPrecision(4)) + viewer.htmlRect(20, 0) + "</nobr> ");

            // Draw a track dot for data points within the plot area
            var yCoor = c.getYCoor(dataSet.getPosition(xIndex), dataSet.getUseYAxis());
            if ((yCoor != null) && (yCoor >= plotArea.getTopY()) && (yCoor <= plotArea.getBottomY()))
                viewer.showTextBox("dataPoint" + i + "_" + j, xCoor, yCoor, JsChartViewer.Center,
                    viewer.htmlRect(7, 7, color));

    // Create the legend by joining the legend entries.
    var legend = "<nobr>[" + c.xAxis().getFormattedLabel(xValue, "mm/dd/yyyy") + "]" + viewer.htmlRect(20, 0) +
        "</nobr> " + legendEntries.reverse().join("");

    // Display the legend on the top of the plot area
    viewer.showTextBox("legend", plotArea.getLeftX(), plotArea.getTopY(), JsChartViewer.BottomLeft, legend,
        "width:" + plotArea.getWidth() + "px;font:bold 11px Arial;padding:3px;-webkit-text-size-adjust:100%;");

<div style="font-size:18pt; font-family:verdana; font-weight:bold">
    Track Line with Legend
<hr style="border:solid 1px #000080" />
<div style="font-size:10pt; font-family:verdana; margin-bottom:1.5em">
    <a href="viewsource.jsp?file=<%=request.getServletPath()%>">View Source Code</a>
<!-- ****** Here is the chart image ****** -->