ChartDirector 6.1 (Java Edition)

Zooming and Scrolling with Track Line (Web)

NOTE: This section describes Zooming and Scrolling with Track Line for web applications only. For Windows applications, please refer to Zooming and Scrolling with Track Line (1) (Windows).

Besides using mouse click and drag for zooming and scrolling, this example has buttons for jumping immediately to display data for the last 30 days, last 90 days, last year or all time. There are check boxes to select the data series to plot, and an update button to immediately update the chart. In addition, the chart includes a track cursor that updates the legend dynamically to display the data values as the mouse cursor moves over the chart.

The main source code listing of this sample program is included at the end of this section. The code consists of the following main parts:

When the script starts to run , the first thing it does is to use WebChartViewer.isPartialUpdateRequest to detect if it is handling an AJAX chart update or an initial page request. If it is an AJAX chart update, it just draws the chart and sends back an AJAX response using WebChartViewer.partialUpdateChart, then terminates the request. If it is an initial page request, it initializes the WebChartViewer, draws the chart, and sends the HTML contents to the browser as usual.

Files in this Demonstration

This sample script requires the following files. When developing your own script using this sample script as a template, please ensure you copy the necessary files to the proper directories (typically the same directory as the script) and reference them using proper paths.

zoomscrolltrack.jspMain source code for this demo.
The images used in the push buttons in this demo.
getchart.jspThe standard utility script used in the image url for retrieving the chart image from
The script file for JsChartViewer, and the supporting cursor and image files. They must be in the same directory.

Source Code Listing

[JSP Version] jspdemo/zoomscrolltrack.jsp
<%@page import="ChartDirector.*, java.util.*"%>
// Initialize the WebChartViewer when the page is first loaded
private void initViewer(WebChartViewer viewer)
    // The full x-axis range is from Jan 1, 2007 to Jan 1, 2012
    Date startDate = new GregorianCalendar(2010, 0, 1).getTime();
    Date endDate = new GregorianCalendar(2015, 0, 1).getTime();
    viewer.setFullRange("x", startDate, endDate);

    // Initialize the view port to show the last 366 days (out of 1826 days)
    viewer.setViewPortWidth(366.0 / 1826);
    viewer.setViewPortLeft(1 - viewer.getViewPortWidth());

    // Set the maximum zoom to 10 days (out of 1826 days)
    viewer.setZoomInWidthLimit(10.0 / 1826);

// Create a random table for demo purpose.
private RanTable getRandomTable()
    RanTable r = new RanTable(127, 4, 1828);
    r.setDateCol(0, new GregorianCalendar(2010, 0, 1).getTime(), 86400);
    r.setCol(1, 150, -10, 10);
    r.setCol(2, 200, -10, 10);
    r.setCol(3, 250, -8, 8);
    return r;

// Draw the chart
private void drawChart(WebChartViewer viewer)
    // Determine the visible x-axis range
    Date viewPortStartDate = Chart.NTime(viewer.getValueAtViewPort("x", viewer.getViewPortLeft()));
    Date viewPortEndDate = Chart.NTime(viewer.getValueAtViewPort("x", viewer.getViewPortLeft() +

    // We need to get the data within the visible x-axis range. In real code, this can be by using a
    // database query or some other means as specific to the application. In this demo, we just
    // generate a random data table, and then select the data within the table.
    RanTable r = getRandomTable();

    // Select the data for the visible date range viewPortStartDate to viewPortEndDate. It is
    // possible there is no data point at exactly viewPortStartDate or viewPortEndDate. In this
    // case, we also need the data points that are just outside the visible date range to "overdraw"
    // the line a little bit (the "overdrawn" part will be clipped to the plot area) In this demo,
    // we do this by adding a one day margin to the date range when selecting the data.
    r.selectDate(0, new Date(viewPortStartDate.getTime() - 86400000), new Date(
        viewPortEndDate.getTime() + 86400000));

    // The selected data from the random data table
    Date[] timeStamps = Chart.NTime(r.getCol(0));
    double[] dataSeriesA = r.getCol(1);
    double[] dataSeriesB = r.getCol(2);
    double[] dataSeriesC = r.getCol(3);

    // Now we have obtained the data, we can plot the chart.

    // Configure overall chart appearance.

    // Create an XYChart object of size 640 x 350 pixels
    XYChart c = new XYChart(640, 350);

    // Set the plotarea at (55, 55) with width 80 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(55, 55, c.getWidth() - 80, c.getHeight() - 90, c.linearGradientColor(0, 55, 0,
        c.getHeight() - 35, 0xf0f6ff, 0xa0c0ff), -1, Chart.Transparent, 0xffffff, 0xffffff);

    // As the data can lie outside the plotarea in a zoomed chart, we need to enable clipping.

    // Add a title to the chart using 18pt Times New Roman Bold Italic font
    c.addTitle("    Zooming and Scrolling with Track Line", "Times New Roman Bold Italic", 18);

    // Set the axis stem to transparent

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

    // Add data to chart

    // In this example, we represent the data by lines. You may modify the code below to use other
    // layer types (areas, scatter plot, etc).

    // Add a line layer for the lines, using a line width of 2 pixels
    LineLayer layer = c.addLineLayer2();

    // In this demo, we do not have too many data points. In real code, the chart may contain a lot
    // of data points when fully zoomed out - much more than the number of horizontal pixels in this
    // plot area. So it is a good idea to use fast line mode.

    // Add up to 3 data series to a line layer, depending on whether the user has selected the data
    // series.
    if (!"F".equals(viewer.getCustomAttr("data0CheckBox"))) {
        layer.addDataSet(dataSeriesA, 0xff3333, "Alpha Series");
    if (!"F".equals(viewer.getCustomAttr("data1CheckBox"))) {
        layer.addDataSet(dataSeriesB, 0x008800, "Beta Series");
    if (!"F".equals(viewer.getCustomAttr("data2CheckBox"))) {
        layer.addDataSet(dataSeriesC, 0x3333cc, "Gamma Series");

    // Configure axis scale and labelling

    // Set the x-axis as a date/time axis with the scale according to the view port x range.
    viewer.syncDateAxisWithViewPort("x", c.xAxis());

    // In this demo, the time range can be from a few years to a few days. We demonstrate how to set
    // up different date/time format based on the time range.

    // If all ticks are yearly aligned, then we use "yyyy" as the label format.
    c.xAxis().setFormatCondition("align", 360 * 86400);

    // If all ticks are monthly aligned, then we use "mmm yyyy" in bold font as the first label of a
    // year, and "mmm" for other labels.
    c.xAxis().setFormatCondition("align", 30 * 86400);
    c.xAxis().setMultiFormat(Chart.StartOfYearFilter(), "<*font=bold*>{value|mmm yyyy}",
        Chart.AllPassFilter(), "{value|mmm}");

    // If all ticks are daily algined, then we use "mmm dd<*br*>yyyy" in bold font as the first
    // label of a year, and "mmm dd" in bold font as the first label of a month, and "dd" for other
    // labels.
    c.xAxis().setFormatCondition("align", 86400);
        "<*block,halign=left*><*font=bold*>{value|mmm dd<*br*>yyyy}", Chart.StartOfMonthFilter(),
        "<*font=bold*>{value|mmm dd}");
    c.xAxis().setMultiFormat2(Chart.AllPassFilter(), "{value|dd}");

    // For all other cases (sub-daily ticks), use "hh:nn<*br*>mmm dd" for the first label of a day,
    // and "hh:nn" for other labels.
    c.xAxis().setMultiFormat(Chart.StartOfDayFilter(), "<*font=bold*>{value|hh:nn<*br*>mmm dd}",
        Chart.AllPassFilter(), "{value|hh:nn}");

    // Step 5 - Output the chart

    // 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

// This script handles both the full page request, as well as the subsequent partial updates (AJAX
// chart updates). We need to determine the type of request first before we processing it.

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

if (viewer.isPartialUpdateRequest()) {
    // Is a partial update request. Draw the chart and perform a partial response.

// If the code reaches here, it is a full page request.

// In this exapmle, we just need to initialize the WebChartViewer and draw the chart.

<!DOCTYPE html>
    <title>Zooming and Scrolling with Track Line</title>
    <script type="text/javascript" src="cdjcv.js"></script>
    <style type="text/css">
        .chartButton { font:12px Verdana; border-bottom:#000000 1px solid; padding:5px; cursor:pointer;}
        .chartButtonSpacer { font:12px Verdana; border-bottom:#000000 1px solid; padding:5px;}
        .chartButton:hover { box-shadow:inset 0px 0px 0px 2px #444488; }
        .chartButtonPressed { background-color: #CCFFCC; }
<body style="margin:0px;">
<script type="text/javascript">

// Execute the following initialization code after the web page is loaded
JsChartViewer.addEventListener(window, 'load', function() {
    // Update the chart when the view port has changed (eg. when the user zooms in using the mouse)
    var viewer = JsChartViewer.get('<%=viewer.getId()%>');
    viewer.attachHandler("ViewPortChanged", viewer.partialUpdate);

    // The Update Chart can also trigger a view port changed event to update the chart.
    document.getElementById("SubmitButton").onclick = function() { viewer.raiseViewPortChangedEvent(); return false; };

    // Before sending the update request to the server, we include the state of the check boxes as custom
    // attributes. The server side charting code will use these attributes to decide the data sets to draw.
    viewer.attachHandler("PreUpdate", function() {
        var checkBoxes = ["data0CheckBox", "data1CheckBox", "data2CheckBox"];
        for (var i = 0; i < checkBoxes.length; ++i)
            viewer.setCustomAttr(checkBoxes[i], document.getElementById(checkBoxes[i]).checked ? "T" : "F");

    // Draw track cursor when mouse is moving over plotarea or if the chart updates
    viewer.attachHandler(["MouseMovePlotArea", "TouchStartPlotArea", "TouchMovePlotArea", "PostUpdate",
        "Now", "ChartMove"], 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%;");

// This method is called when the user clicks on the Pointer, Zoom In or Zoom Out buttons
function setMouseMode(mode)
    var viewer = JsChartViewer.get('<%=viewer.getId()%>');
    if (mode == viewer.getMouseUsage())
        mode = JsChartViewer.Default;

    // Set the button color based on the selected mouse mode
    document.getElementById("scrollButton").className = "chartButton" +
        ((mode  == JsChartViewer.Scroll) ? " chartButtonPressed" : "");
    document.getElementById("zoomInButton").className = "chartButton" +
        ((mode  == JsChartViewer.ZoomIn) ? " chartButtonPressed" : "");
    document.getElementById("zoomOutButton").className = "chartButton" +
        ((mode  == JsChartViewer.ZoomOut) ? " chartButtonPressed" : "");

    // Set the mouse mode

// This method is called when the user clicks on the buttons that selects the last NN days
function setTimeRange(duration)
    var viewer = JsChartViewer.get('<%=viewer.getId()%>');

    // Set the view port width to represent the required duration (as a ratio to the total x-range)
        duration / (viewer.getValueAtViewPort("x", 1) - viewer.getValueAtViewPort("x", 0))));

    // Set the view port left so that the view port is moved to show the latest data
    viewer.setViewPortLeft(1 - viewer.getViewPortWidth());

    // Trigger a view port change event

<form method="post">
<table cellspacing="0" cellpadding="0" style="border:black 1px solid;">
        <td align="right" colspan="2" style="background:#000088; color:#ffff00; padding:0px 4px 2px 0px;">
            <a style="color:#FFFF00; font:italic bold 10pt Arial; text-decoration:none" href="">
                Advanced Software Engineering
    <tr valign="top">
        <td style="width:130px; background:#c0c0ff;">
        <div style="width:130px">
            <!-- The following table is to create 3 cells for 3 buttons to control the mouse usage mode. -->
            <table style="width:100%; padding:0px; border:0px; border-spacing:0px;">
                    <td class="chartButton" id="scrollButton" onclick="setMouseMode(JsChartViewer.Scroll)"
                        ontouchstart="this.onclick(event); event.preventDefault();">
                        <img src="scrollew.gif" style="vertical-align:middle" alt="Drag" />&nbsp;&nbsp;Drag to Scroll
                    <td class="chartButton" id="zoomInButton" onclick="setMouseMode(JsChartViewer.ZoomIn)"
                        ontouchstart="this.onclick(event); event.preventDefault();">
                        <img src="zoomInIcon.gif" style="vertical-align:middle" alt="Zoom In" />&nbsp;&nbsp;Zoom In
                    <td class="chartButton" id="zoomOutButton" onclick="setMouseMode(JsChartViewer.ZoomOut)"
                        ontouchstart="this.onclick(event); event.preventDefault();">
                        <img src="zoomOutIcon.gif" style="vertical-align:middle" alt="Zoom Out" />&nbsp;&nbsp;Zoom Out
                    <td class="chartButtonSpacer">
                        <div style="padding:2px">&nbsp;</div>
                    <td class="chartButton" onclick="setTimeRange(30 * 86400);"
                        ontouchstart="this.onclick(event); event.preventDefault();">
                        <img src="goto.gif" style="vertical-align:middle" alt="Last 30 days" />&nbsp;&nbsp;Last 30 days
                    <td class="chartButton" onclick="setTimeRange(90 * 86400);"
                        ontouchstart="this.onclick(event); event.preventDefault();">
                        <img src="goto.gif" style="vertical-align:middle" alt="Last 90 days" />&nbsp;&nbsp;Last 90 days
                    <td class="chartButton" onclick="setTimeRange(366 * 86400);"
                        ontouchstart="this.onclick(event); event.preventDefault();">
                        <img src="goto.gif" style="vertical-align:middle" alt="Last Year" />&nbsp;&nbsp;Last Year
                    <td class="chartButton" onclick="setTimeRange(1E15);"
                        ontouchstart="this.onclick(event); event.preventDefault();">
                        <img src="goto.gif" style="vertical-align:middle" alt="All Time" />&nbsp;&nbsp;All Time
            <div style="font:9pt Verdana; line-height:1.5; padding-top:25px">
            <input id="data0CheckBox" type="checkbox" checked="checked" /> Alpha Series<br />
            <input id="data1CheckBox" type="checkbox" checked="checked" /> Beta Series<br />
            <input id="data2CheckBox" type="checkbox" checked="checked" /> Gamma Series<br />
            <div style="font:9pt Verdana; margin-top:15px; text-align:center">
                <input type="submit" id="SubmitButton" name="SubmitButton" value="Update Chart" />
        <td style="border-left:black 1px solid; padding:10px 5px 0px 5px;">
            <!-- ****** Here is the chart image ****** -->