backgrounddraggingmanipulator.java

JPowerGraph is a Java library for creating directed graphs for SWT. It supports graph movement, sele

package net.sourceforge.jpowergraph.manipulator.dragging;


import net.sourceforge.jpowergraph.lens.CursorLens;
import net.sourceforge.jpowergraph.manipulator.AbstractManipulator;

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.MouseEvent;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;

/**
 * A manipulator enabling the dragging of the graph's background.
 */
public class BackgroundDraggingManipulator extends AbstractManipulator {
    /** The name of this manipulator. */
    public static final String NAME="BackgroundDraggingManipulator";

    /** The position where the mouse was grabbed. */
    protected Point m_grabPosition;
    
    private int mouseEventKeyMask = SWT.NONE;

    private CursorLens cursorLens;

    private boolean disposed = false;
    
    /**
     * Creates an instance of this class.
     * 
     * Dragging the background can be done by holding down the shift key
     * and left clicking.
     */
    public BackgroundDraggingManipulator(CursorLens theCursorLens) {
        this(theCursorLens, SWT.SHIFT);
    }
    
    /**
     * Creates an instance of this class.
     * 
     * Dragging the background can be done by holding down the key specified in
     * theMouseKeyAssist and left clicking. The key mask can be one of:
     * 
     * SWT.SHIFT
     * SWT.CTRL
     * SWT.ALT
     * SWT.NONE (for no key mask)
     * 
     * @param theMouseEventKeyMask The Mouse MASK
     */
    public BackgroundDraggingManipulator(CursorLens theCursorLens, int theMouseEventKeyMask) {
        cursorLens = theCursorLens;
        mouseEventKeyMask = theMouseEventKeyMask;
    }
    
    public String getName() {
        return NAME;
    }
    public boolean isDragging() {
        return m_grabPosition!=null;
    }
    public void mouseDown(MouseEvent e) {
        if (m_graphPane.isEnabled() && e.button == 1 && isStartBackgroundDraggingEvent(e)) {
            Point point = new Point(e.x, e.y);
            if (m_graphPane.getNodeAtPoint(point)==null && m_graphPane.getNearestEdge(point)==null) {
                m_grabPosition=point;
                cursorLens.setCursor(CursorLens.hand);
            }
        }
    }
    public void mouseReleased(MouseEvent e) {
        if (isDragging()) {
            performDrag(new Point(e.x, e.y));
            cursorLens.setCursor(null);
            m_grabPosition=null;
        }
    }
    public void mouseDragged(MouseEvent e) {
        if (isDragging()) {
            performDrag(new Point(e.x, e.y));
        }
    }
    protected void performDrag(Point position) {
        Rectangle rectangle=m_graphPane.getClientArea();
        rectangle.x+=m_grabPosition.x-position.x;
        rectangle.y+=m_grabPosition.y-position.y;
        m_graphPane.scrollRectToVisible(rectangle);
        m_grabPosition=position;
    }
    
    protected boolean isStartBackgroundDraggingEvent(MouseEvent e) {
        if (mouseEventKeyMask == SWT.NONE){
            return true;
        }
        return (e.stateMask & mouseEventKeyMask) != 0;
    }
    
    public void dispose(){
        disposed = true;
    }
    
    public boolean isDisposed(){
        return disposed ;
    }
}