org.eclipse.gmf.runtime.diagram.ui/src/org/eclipse/gmf/runtime/diagram/ui/internal/editpolicies/DelegatingMouseEventsEditPolicy.java

/******************************************************************************
 * Copyright (c) 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    IBM Corporation - initial API and implementation 
 ****************************************************************************/

package org.eclipse.gmf.runtime.diagram.ui.internal.editpolicies;

import org.eclipse.draw2d.MouseEvent;
import org.eclipse.draw2d.MouseMotionListener;
import org.eclipse.draw2d.geometry.Point;
import org.eclipse.gef.EditPart;
import org.eclipse.gef.EditPolicy;
import org.eclipse.gef.editpolicies.AbstractEditPolicy;
import org.eclipse.gmf.runtime.diagram.ui.editparts.IGraphicalEditPart;
import org.eclipse.gmf.runtime.diagram.ui.editparts.TopGraphicEditPart;

/**
 * This editpolicy forwards all mouse events to the editpolicy installed on its
 * nearest parent. The editpolicy to delegate to must implement the
 * <code>MouseMotionListener</code> interface.
 * 
 * @author cmahoney
 */
public class DelegatingMouseEventsEditPolicy
    extends AbstractEditPolicy
    implements MouseMotionListener {

    /** The editpolicy role used to retrieve the editpolicy from the parent. */
    private final String editPolicyRole;

    /**
     * Creates a new instance.
     * 
     * @param editPolicyRole
     *            The editpolicy role used to retrieve the editpolicy from the
     *            parent.
     */
    public DelegatingMouseEventsEditPolicy(String editPolicyRole) {
        super();
        this.editPolicyRole = editPolicyRole;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.eclipse.gef.EditPolicy#activate()
     */
    public void activate() {
        super.activate();

        ((IGraphicalEditPart) getHost()).getFigure().addMouseMotionListener(
            this);
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.eclipse.gef.EditPolicy#deactivate()
     */
    public void deactivate() {
        ((IGraphicalEditPart) getHost()).getFigure().removeMouseMotionListener(
            this);

        super.deactivate();
    }

    /**
     * Traverses the parent editpart hierarchy to find the first parent with an
     * editpolicy of the appropriate role installed that implements the
     * <code>MouseMotionListener</code> interface. Stops if a parent is a
     * <code>TopGraphicEditPart</code>.
     * 
     * @return the parent editpolicy role or null if none was found
     */
    private EditPolicy getParentEditPolicy() {
        EditPart parentEP = getHost().getParent();
        while (parentEP != null) {
            EditPolicy editPolicy = parentEP.getEditPolicy(editPolicyRole);
            if (editPolicy != null && editPolicy instanceof MouseMotionListener) {
                return editPolicy;
            }
            if (parentEP instanceof TopGraphicEditPart) {
                return null;
            }
            parentEP = parentEP.getParent();
        }
        return null;
    }

    /**
     * Forwards this mouse event to the first parent of the host editpart that
     * has the applicable editpolicy installed.
     */
    public void mouseEntered(MouseEvent me) {
        MouseMotionListener parentPolicy = (MouseMotionListener) getParentEditPolicy();
        if (parentPolicy != null) {
            translateLocation(me);            
            parentPolicy.mouseEntered(me);
        }
    }

    /**
     * Forwards this mouse event to the first parent of the host editpart that
     * has the applicable editpolicy installed.
     */
    public void mouseExited(MouseEvent me) {
        MouseMotionListener parentPolicy = (MouseMotionListener) getParentEditPolicy();
        if (parentPolicy != null) {
            translateLocation(me);            
            parentPolicy.mouseExited(me);
        }
    }

    /**
     * Forwards this mouse event to the first parent of the host editpart that
     * has the applicable editpolicy installed.
     */
    public void mouseHover(MouseEvent me) {
        MouseMotionListener parentPolicy = (MouseMotionListener) getParentEditPolicy();
        if (parentPolicy != null) {
            translateLocation(me);            
            parentPolicy.mouseHover(me);
        }
    }

    /**
     * Forwards this mouse event to the first parent of the host editpart that
     * has the applicable editpolicy installed.
     */
    public void mouseMoved(MouseEvent me) {
        MouseMotionListener parentPolicy = (MouseMotionListener) getParentEditPolicy();
        if (parentPolicy != null) {
            translateLocation(me);            
            parentPolicy.mouseMoved(me);
        }
    }

    /**
     * Forwards this mouse event to the first parent of the host editpart that
     * has the applicable editpolicy installed.
     */
    public void mouseDragged(MouseEvent me) {
        MouseMotionListener parentPolicy = (MouseMotionListener) getParentEditPolicy();
        if (parentPolicy != null) {
            translateLocation(me);            
            parentPolicy.mouseDragged(me);
        }
    }

    /**
     * Updates the location in the <code>MouseEvent</code> to be relative to
     * the host figure of the editpolicy being delegated to.
     * 
     * @param mouseEvent
     *            the mouse event whose location will be updated
     */
    private void translateLocation(MouseEvent mouseEvent) {
        Point location = mouseEvent.getLocation();
        ((IGraphicalEditPart) getHost()).getFigure().translateToAbsolute(
            location);
        ((IGraphicalEditPart) getParentEditPolicy().getHost()).getFigure()
            .translateToRelative(location);
        mouseEvent.x = location.x;
        mouseEvent.y = location.y;
    }
}