bundles/org.eclipse.gef/src/org/eclipse/gef/editpolicies/SelectionHandlesEditPolicy.java

/*******************************************************************************
 * Copyright (c) 2000, 2010 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 java.util.ArrayList;
import java.util.List;

import org.eclipse.core.runtime.IAdaptable;

import org.eclipse.draw2d.IFigure;
import org.eclipse.draw2d.geometry.Point;

import org.eclipse.gef.AccessibleHandleProvider;
import org.eclipse.gef.Handle;
import org.eclipse.gef.LayerConstants;

/**
 * A SelectionEditPolicy which manages a List of handles provided by the
 * subclass. Handles are Figures which are added to the HANDLE layer, and
 * generally return a DragTracker for dragging them. Handles are accessible for
 * keyboard use if they return an accessible location.
 * <P>
 * SelectionHandlesEditPolicy implements
 * {@link org.eclipse.core.runtime.IAdaptable} for accessibility support. If any
 * of the managed Handles provide accesible locations, then a
 * {@link org.eclipse.gef.AccessibleHandleProvider} is automatically created.
 * 
 * @since 2.0
 */
public abstract class SelectionHandlesEditPolicy extends SelectionEditPolicy
		implements IAdaptable {

	/**
	 * the List of handles
	 */
	protected List handles;

	/**
	 * Adds the handles to the handle layer.
	 */
	protected void addSelectionHandles() {
		removeSelectionHandles();
		IFigure layer = getLayer(LayerConstants.HANDLE_LAYER);
		handles = createSelectionHandles();
		for (int i = 0; i < handles.size(); i++)
			layer.add((IFigure) handles.get(i));
	}

	/**
	 * Subclasses must implement to provide the list of handles.
	 * 
	 * @return List of handles; cannot be <code>null</code>
	 */
	protected abstract List createSelectionHandles();

	/**
	 * @see org.eclipse.core.runtime.IAdaptable#getAdapter(Class)
	 */
	public Object getAdapter(Class key) {
		if (key == AccessibleHandleProvider.class)
			return new AccessibleHandleProvider() {
				public List getAccessibleHandleLocations() {
					List result = new ArrayList();
					if (handles != null) {
						for (int i = 0; i < handles.size(); i++) {
							Point p = ((Handle) handles.get(i))
									.getAccessibleLocation();
							if (p != null)
								result.add(p);
						}
					}
					return result;
				}
			};
		return null;
	}

	/**
	 * Implemented to remove the handles.
	 * 
	 * @see org.eclipse.gef.editpolicies.SelectionEditPolicy#hideSelection()
	 */
	protected void hideSelection() {
		removeSelectionHandles();
	}

	/**
	 * removes the selection handles from the selection layer.
	 */
	protected void removeSelectionHandles() {
		if (handles == null)
			return;
		IFigure layer = getLayer(LayerConstants.HANDLE_LAYER);
		for (int i = 0; i < handles.size(); i++)
			layer.remove((IFigure) handles.get(i));
		handles = null;
	}

	/**
	 * Implemented to add the selection handles
	 * 
	 * @see org.eclipse.gef.editpolicies.SelectionEditPolicy#showSelection()
	 */
	protected void showSelection() {
		addSelectionHandles();
	}

}