SWTChart mouse over handling

I have found SWTChart library and just wonder how it would be possible to go over the below graph with the mouse and get box with the info about the y-value like in this example.

_{(source: swtchart.org)}

package org.swtchart.examples;

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.swtchart.Chart;
import org.swtchart.ILineSeries;
import org.swtchart.ISeries.SeriesType;

/**
* An example for area chart.
*/
public class AreaChartExample {

    private static final double[] ySeries1 = { 0.1, 0.38, 0.71, 0.92, 1.0 };

    private static final double[] ySeries2 = { 1.2, 3.53, 3.1, 0.1, 0.5 };

    /**
    * The main method.
    * 
    * @param args
    *            the arguments
    */
    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setText("Area Chart");
        shell.setSize(500, 400);
        shell.setLayout(new FillLayout());

        createChart(shell);

        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
    }

    /**
    * create the chart.
    * 
    * @param parent
    *            The parent composite
    * @return The created chart
    */
    static public Chart createChart(Composite parent) {

        // create a chart
        Chart chart = new Chart(parent, SWT.NONE);

        // set titles
        chart.getTitle().setText("Area Chart");

        // create line series
        ILineSeries lineSeries1 = (ILineSeries) chart.getSeriesSet()
                .createSeries(SeriesType.LINE, "line series 1");
        lineSeries1.setYSeries(ySeries1);
        lineSeries1.setLineColor(Display.getDefault().getSystemColor(
                SWT.COLOR_RED));
        lineSeries1.enableArea(true);

        ILineSeries lineSeries2 = (ILineSeries) chart.getSeriesSet()
                .createSeries(SeriesType.LINE, "line series 2");
        lineSeries2.setYSeries(ySeries2);
        lineSeries2.enableArea(true);

        // adjust the axis range
        chart.getAxisSet().adjustRange();

        return chart;
    }
}

How is it possible to include a mouse event to open a box with the y-value like in the above example?

Thank you in advance.

Solution

Got it working. My code will search for the closest data point to the mouse position, display its coordinates in the tooltip and highlight the data point in the plot:

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
import org.swtchart.Chart;
import org.swtchart.IAxis;
import org.swtchart.ILineSeries;
import org.swtchart.ISeries;
import org.swtchart.ISeries.SeriesType;

/**
 * An example for area chart.
 */
public class AreaChartExample {

    private static final double[] ySeries1 = { 0.1, 0.38, 0.71, 0.92, 1.0 };

    private static final double[] ySeries2 = { 1.2, 3.53, 3.1, 0.1, 0.5 };

    /* Used to remember the location of the highlight point */
    private static int highlightX;
    private static int highlightY;

    /**
     * The main method.
     * 
     * @param args
     *            the arguments
     */
    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setText("Area Chart");
        shell.setSize(500, 400);
        shell.setLayout(new FillLayout());

        createChart(shell);

        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
    }

    protected static boolean highlight;

    /**
     * create the chart.
     * 
     * @param parent
     *            The parent composite
     * @return The created chart
     */
    static public Chart createChart(Composite parent) {

        // create a chart
        final Chart chart = new Chart(parent, SWT.NONE);

        // set titles
        chart.getTitle().setText("Area Chart");

        // create line series
        ILineSeries lineSeries1 = (ILineSeries) chart.getSeriesSet()
                .createSeries(SeriesType.LINE, "line series 1");
        lineSeries1.setYSeries(ySeries1);
        lineSeries1.setLineColor(Display.getDefault().getSystemColor(
                SWT.COLOR_RED));
        lineSeries1.enableArea(true);

        ILineSeries lineSeries2 = (ILineSeries) chart.getSeriesSet()
                .createSeries(SeriesType.LINE, "line series 2");
        lineSeries2.setYSeries(ySeries2);
        lineSeries2.enableArea(true);

        // adjust the axis range
        chart.getAxisSet().adjustRange();

        /* Get the plot area and add the mouse listeners */
        final Composite plotArea = chart.getPlotArea();

        plotArea.addListener(SWT.MouseHover, new Listener() {

            @Override
            public void handleEvent(Event event) {
                IAxis xAxis = chart.getAxisSet().getXAxis(0);
                IAxis yAxis = chart.getAxisSet().getYAxis(0);

                double x = xAxis.getDataCoordinate(event.x);
                double y = yAxis.getDataCoordinate(event.y);

                ISeries[] series = chart.getSeriesSet().getSeries();

                double closestX = 0;
                double closestY = 0;
                double minDist = Double.MAX_VALUE;

                /* over all series */
                for (ISeries serie : series) {
                    double[] xS = serie.getXSeries();
                    double[] yS = serie.getYSeries();

                    /* check all data points */
                    for (int i = 0; i < xS.length; i++) {
                        /* compute distance to mouse position */
                        double newDist = Math.sqrt(Math.pow((x - xS[i]), 2)
                                + Math.pow((y - yS[i]), 2));

                        /* if closer to mouse, remember */
                        if (newDist < minDist) {
                            minDist = newDist;
                            closestX = xS[i];
                            closestY = yS[i];
                        }
                    }
                }

                /* set tooltip of closest data point */
                plotArea.setToolTipText(closestX + " " + closestY);

                /* remember closest data point */
                highlightX = xAxis.getPixelCoordinate(closestX);
                highlightY = yAxis.getPixelCoordinate(closestY);

                highlight = true;

                /* trigger repaint (paint highlight) */
                plotArea.redraw();
            }
        });

        plotArea.addListener(SWT.MouseMove, new Listener() {

            @Override
            public void handleEvent(Event arg0) {
                highlight = false;

                plotArea.redraw();
            }
        });

        plotArea.addListener(SWT.Paint, new Listener() {

            @Override
            public void handleEvent(Event event) {
                if (highlight) {
                    GC gc = event.gc;

                    gc.setBackground(Display.getDefault().getSystemColor(
                            SWT.COLOR_RED));
                    gc.setAlpha(128);

                    gc.fillOval(highlightX - 5, highlightY - 5, 10, 10);
                }
            }
        });

        return chart;
    }
}

The result looks like this:

enter image description here