MoveLineChartByMouseListener.java

package de.slothsoft.charts.swt;

import java.util.Objects;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.MouseEvent;
import org.eclipse.swt.events.MouseListener;
import org.eclipse.swt.events.MouseMoveListener;
import org.eclipse.swt.events.MouseWheelListener;
import org.eclipse.swt.graphics.Cursor;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;

import de.slothsoft.charts.Area;
import de.slothsoft.charts.linechart.LineChart;

/**
 * A {@link MouseListener}, {@link MouseMoveListener} and {@link MouseWheelListener} to
 * move the diagram with the mouse. It's advised to add this listener by using the
 * {@link MoveLineChartByMouseListener#hookToControl(Control, LineChart)} method.
 *
 * @author Stef Schulz
 * @since 0.1.0
 */

public class MoveLineChartByMouseListener implements MouseListener, MouseMoveListener, MouseWheelListener {

    /**
     * Creates a new {@link MoveLineChartByMouseListener}, hooks it to a control (not
     * necessary a {@link ChartControl}, but that's probably a good idea) and returns the
     * brand new instance.
     *
     * @param control the control, probably a {@link ChartControl}
     * @param chart the displayed chart
     * @return the brand new listener
     */

    public static MoveLineChartByMouseListener hookToControl(Control control, LineChart chart) {
        final MoveLineChartByMouseListener result = new MoveLineChartByMouseListener(chart);
        control.addMouseListener(result);
        control.addMouseMoveListener(result);
        control.addMouseWheelListener(result);
        return result;
    }

    private static Cursor handCursor;

    static Cursor getHandCursor(Display display) {
        if (handCursor == null) {
            handCursor = new Cursor(display, SWT.CURSOR_HAND);
        }
        return handCursor;
    }

    private final LineChart chart;
    boolean mouseDown;
    private int mouseDownX;
    private int mouseDownY;

    private int movementMouseButton = 1;

    /**
     * Constructor.
     *
     * @param chart the chart this listener uses
     */

    public MoveLineChartByMouseListener(LineChart chart) {
        this.chart = Objects.requireNonNull(chart);
    }

    @Override
    public void mouseDoubleClick(MouseEvent e) {
        // nothing to do yet
    }

    @Override
    public void mouseDown(MouseEvent e) {
        if (isInGraphArea(e) && e.button == this.movementMouseButton) {
            this.mouseDown = true;
            this.mouseDownX = e.x;
            this.mouseDownY = e.y;
        }
    }

    @Override
    public void mouseUp(MouseEvent e) {
        if (e.button == this.movementMouseButton) {
            this.mouseDown = false;
        }
    }

    @Override
    public void mouseMove(MouseEvent e) {
        final Control control = ((Control) e.widget);
        if (isInGraphArea(e)) {
            control.setCursor(getHandCursor(control.getDisplay()));
        } else {
            control.setCursor(null);
        }

        if (this.mouseDown) {
            final int diffX = this.mouseDownX - e.x;
            final int diffY = e.y - this.mouseDownY; // for line charts y is flipped

            this.chart.moveDisplayedAreaByChartCoordinates(diffX, diffY);

            this.mouseDownX = e.x;
            this.mouseDownY = e.y;
        }
    }

    private boolean isInGraphArea(MouseEvent e) {
        final Control control = ((Control) e.widget);
        final Point controlSize = control.getSize();
        final Area actualArea = this.chart.calculateGraphArea(controlSize.x, controlSize.y);
        return actualArea.containsPoint(e.x, e.y);
    }

    @Override
    public void mouseScrolled(MouseEvent e) {
        if (isInGraphArea(e)) {
            if (e.count < 0) {
                this.chart.zoomDisplayedAreaOutByChartCoordinates(e.x, e.y);
            } else {
                this.chart.zoomDisplayedAreaInByChartCoordinates(e.x, e.y);
            }
        }
    }

    /**
     * Returns the button that needs to be pressed to move the chart.
     * <ul>
     * <li>1 for the first button (usually 'left')</li>
     * <li>2 for the second button (usually 'middle')</li>
     * <li>3 for the third button (usually 'right')</li>
     * <li>etc.</li>
     * </ul>
     *
     * @return the mouse button
     */

    public int getMovementMouseButton() {
        return this.movementMouseButton;
    }

    /**
     * Sets the button that needs to be pressed to move the chart.
     * <ul>
     * <li>1 for the first button (usually 'left')</li>
     * <li>2 for the second button (usually 'middle')</li>
     * <li>3 for the third button (usually 'right')</li>
     * <li>etc.</li>
     * </ul>
     *
     * @param newMovementMouseButton the mouse button
     * @return this instance
     */

    public MoveLineChartByMouseListener movementMouseButton(int newMovementMouseButton) {
        setMovementMouseButton(newMovementMouseButton);
        return this;
    }

    /**
     * Sets the button that needs to be pressed to move the chart.
     * <ul>
     * <li>1 for the first button (usually 'left')</li>
     * <li>2 for the second button (usually 'middle')</li>
     * <li>3 for the third button (usually 'right')</li>
     * <li>etc.</li>
     * </ul>
     *
     * @param movementMouseButton the mouse button
     */

    public void setMovementMouseButton(int movementMouseButton) {
        this.movementMouseButton = movementMouseButton;
    }

}