GraphicalEditPolicy.java

/*******************************************************************************
 * Copyright (c) 2000, 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.gef.editpolicies;

import org.eclipse.draw2d.IFigure;

import org.eclipse.gef.GraphicalEditPart;
import org.eclipse.gef.LayerConstants;
import org.eclipse.gef.editparts.LayerManager;

/**
 * A <code>GraphicalEditPolicy</code> is used with a {@link GraphicalEditPart}. All
 * GraphicalEditPolicies are involved with the Figure in some way. They might use the
 * Figure to interpret Requests, or they might simply decorate the Figure with graphical
 * Feedback, such as selection handles.
 * <P>
 * This class provides convenience methods for accessing the host's Figure, and for adding
 * <i>feedback</i> to the GraphicalViewer. This class does not handle any Request types
 * directly.
 */
public abstract class GraphicalEditPolicy
	extends AbstractEditPolicy
{

/**
 * Adds the specified <code>Figure</code> to the {@link LayerConstants#FEEDBACK_LAYER}.
 * @param figure the feedback to add
 */
protected void addFeedback(IFigure figure) {
	getFeedbackLayer().add(figure);
}

/**
 * Returns the layer used for displaying feedback.
 *  
 * @return the feedback layer
 */
protected IFigure getFeedbackLayer() {
	return getLayer(LayerConstants.FEEDBACK_LAYER);
}

/**
 * Convenience method to return the host's Figure.
 * @return The host GraphicalEditPart's Figure
 */
protected IFigure getHostFigure() {
	return ((GraphicalEditPart)getHost()).getFigure();
}

/**
 * Obtains the specified layer.
 * @param layer the key identifying the layer
 * @return the requested layer
 */
protected IFigure getLayer(Object layer) {
	return LayerManager.Helper.find(getHost()).getLayer(layer);
}

/**
 * Removes the specified <code>Figure</code> from the {@link
 * LayerConstants#FEEDBACK_LAYER}.
 * @param figure the feedback to remove
 */
protected void removeFeedback(IFigure figure) {
	getFeedbackLayer().remove(figure);
}

}