SWTChart mouse event handling

Question

I have found SWTChart library and just wonder how it would be possible to select with the mouse a range e.g. 1 to 3 on the x-axis and I would get all y-axis values which belongs to the selected x values.

_{(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 for selecting a range in the above example?

Thank you in advance.

Answer 1

The following code should give you an idea on how to do this. Basically, you have to get the chartArea of the chart, add the listeners for SWT.MouseDown and SWT.MouseUp and remember the position of both events. To answer your comment: Yes, you can add a "highlight" functionality by using the SWT.Paint listener.

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.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 location point of mouse down */
        private static double startX;
        private static double startY;

        private static int startXPos;
        private static int startYPos;

        private static int currentX;
        private static int currentY;

        private static boolean drag = false;

        /**
        * 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
            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.MouseDown, new Listener() {

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

                    startX = xAxis.getDataCoordinate(event.x);
                    startY = yAxis.getDataCoordinate(event.y);

                    startXPos = event.x;
                    startYPos = event.y;

                    drag = true;
                }
            });

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

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

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

                    System.out.println(startX + " " + endX);
                    System.out.println(startY + " " + endY);

                    drag = false;

                    plotArea.redraw();
                }
            });

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

                @Override
                public void handleEvent(Event event) {
                    if(drag)
                    {
                        currentX = event.x;
                        currentY = event.y;

                        plotArea.redraw();
                    }
                }
            });

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

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

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

                        int minX = Math.min(startXPos, currentX);
                        int minY = Math.min(startYPos, currentY);

                        int maxX = Math.max(startXPos, currentX);
                        int maxY = Math.max(startYPos, currentY);

                        int width = maxX - minX;
                        int height = maxY - minY;

                        gc.fillRectangle(minX, minY, width, height);
                    }
                }
            });

            return chart;
        }
    }