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This plug-in contains the bulk of the Workbench implementation, and depends on JFace, SWT, and Core Runtime. It cannot be used independently from org.eclipse.ui. Workbench client plug-ins should not depend directly on this plug-in.
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/*******************************************************************************
 * Copyright (c) 2000, 2006 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.ui.actions;

import org.eclipse.jface.action.Action;
import org.eclipse.ui.IPartListener;
import org.eclipse.ui.IWorkbenchPart;

/**
 * The abstract superclass for actions that listen to part activation and
 * open/close events. This implementation tracks the active part (see 
 * getActivePart) and provides a convenient place to monitor
 * part lifecycle events that could affect the availability of the action.
 * 
 * Subclasses must implement the following IAction method:
 * 

 *   run - to do the action's work
 * 
 * 
 * 
 * Subclasses may extend any of the IPartListener methods if the
 * action availablity needs to be recalculated:
 * 

 *   partActivated 
 *   partDeactivated
 *   partOpened
 *   partClosed
 *   partBroughtToTop
 * 
 * 
 * 
 * Although this method implements the IPartListener interface,
 * it does NOT register itself. 
 * 
 */
public abstract class PartEventAction extends Action implements IPartListener {

    /**
     * The active part, or null if none.
     */
    private IWorkbenchPart activePart;

    /**
     * Creates a new action with the given text.
     *
     * @param text the action's text, or null if there is no text
     */
    protected PartEventAction(String text) {
        super(text);
    }

    /**
     * Creates a new action with the given text and style.
     *
     * @param text the action's text, or null if there is no text
     * @param style one of AS_PUSH_BUTTON, AS_CHECK_BOX,
     * 		AS_DROP_DOWN_MENU, AS_RADIO_BUTTON, and
     * 		AS_UNSPECIFIED
     * @since 3.0
     */
    protected PartEventAction(String text, int style) {
        super(text, style);
    }

    /**
     * Returns the currently active part in the workbench.
     *
     * @return currently active part in the workbench, or null if none
     */
    public IWorkbenchPart getActivePart() {
        return activePart;
    }

    /**
     * The PartEventAction implementation of this 
     * IPartListener method records that the given part is active.
     * Subclasses may extend this method if action availability has to be
     * recalculated.
     */
    public void partActivated(IWorkbenchPart part) {
        activePart = part;
    }

    /**
     * The PartEventAction implementation of this 
     * IPartListener method does nothing. Subclasses should extend
     * this method if action availability has to be recalculated.
     */
    public void partBroughtToTop(IWorkbenchPart part) {
        // do nothing
    }

    /**
     * The PartEventAction implementation of this 
     * IPartListener method clears the active part if it just closed.
     * Subclasses may extend this method if action availability has to be
     * recalculated.
     */
    public void partClosed(IWorkbenchPart part) {
        if (part == activePart) {
			activePart = null;
		}
    }

    /**
     * The PartEventAction implementation of this 
     * IPartListener method records that there is no active part.
     * Subclasses may extend this method if action availability has to be
     * recalculated.
     */
    public void partDeactivated(IWorkbenchPart part) {
        activePart = null;
    }

    /**
     * The PartEventAction implementation of this 
     * IPartListener method does nothing. Subclasses should extend
     * this method if action availability has to be recalculated.
     */
    public void partOpened(IWorkbenchPart part) {
        // do nothing
    }
}