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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package javax.swing.undo;

import javax.swing.event.*;

import java.util.*;

/**

 * A support class used for managing <code>UndoableEdit</code> listeners.

 *

 * @author Ray Ryan

 */

public class UndoableEditSupport {

    protected int updateLevel;

    protected CompoundEdit compoundEdit;

    protected Vector<UndoableEditListener> listeners;

    protected Object realSource;

    /**

     * Constructs an <code>UndoableEditSupport</code> object.

     */

    public UndoableEditSupport() {

        this(null);

    }

    /**

     * Constructs an <code>UndoableEditSupport</code> object.

     *

     * @param r  an <code>Object</code>

     */

    public UndoableEditSupport(Object r) {

        realSource = r == null ? this : r;

        updateLevel = 0;

        compoundEdit = null;

        listeners = new Vector<UndoableEditListener>();

    }

    /**

     * Registers an <code>UndoableEditListener</code>.

     * The listener is notified whenever an edit occurs which can be undone.

     *

     * @param l  an <code>UndoableEditListener</code> object

     * @see #removeUndoableEditListener

     */

    public synchronized void addUndoableEditListener(UndoableEditListener l) {

        listeners.addElement(l);

    }

    /**

     * Removes an <code>UndoableEditListener</code>.

     *

     * @param l  the <code>UndoableEditListener</code> object to be removed

     * @see #addUndoableEditListener

     */

    public synchronized void removeUndoableEditListener(UndoableEditListener l)

    {

        listeners.removeElement(l);

    }

    /**

     * Returns an array of all the <code>UndoableEditListener</code>s added

     * to this UndoableEditSupport with addUndoableEditListener().

     *

     * @return all of the <code>UndoableEditListener</code>s added or an empty

     *         array if no listeners have been added

     * @since 1.4

     */

    public synchronized UndoableEditListener[] getUndoableEditListeners() {

        return listeners.toArray(new UndoableEditListener[0]);

    }

    /**

     * Called only from <code>postEdit</code> and <code>endUpdate</code>. Calls

     * <code>undoableEditHappened</code> in all listeners. No synchronization

     * is performed here, since the two calling methods are synchronized.

     *

     * @param e edit to be verified

     */

    protected void _postEdit(UndoableEdit e) {

        UndoableEditEvent ev = new UndoableEditEvent(realSource, e);

        @SuppressWarnings("unchecked")

        Enumeration<UndoableEditListener> cursor =

            ((Vector<UndoableEditListener>)listeners.clone()).elements();

        while (cursor.hasMoreElements()) {

            cursor.nextElement().undoableEditHappened(ev);

        }

    }

    /**

     * DEADLOCK WARNING: Calling this method may call

     * <code>undoableEditHappened</code> in all listeners.

     * It is unwise to call this method from one of its listeners.

     *

     * @param e edit to be posted

     */

    public synchronized void postEdit(UndoableEdit e) {

        if (updateLevel == 0) {

            _postEdit(e);

        } else {

            // PENDING(rjrjr) Throw an exception if this fails?

            compoundEdit.addEdit(e);

        }

    }

    /**

     * Returns the update level value.

     *

     * @return an integer representing the update level

     */

    public int getUpdateLevel() {

        return updateLevel;

    }

    /**

     *

     */

    public synchronized void beginUpdate() {

        if (updateLevel == 0) {

            compoundEdit = createCompoundEdit();

        }

        updateLevel++;

    }

    /**

     * Called only from <code>beginUpdate</code>.

     * Exposed here for subclasses' use.

     *

     * @return new created {@code CompoundEdit} object

     */

    protected CompoundEdit createCompoundEdit() {

        return new CompoundEdit();

    }

    /**

     * DEADLOCK WARNING: Calling this method may call

     * <code>undoableEditHappened</code> in all listeners.

     * It is unwise to call this method from one of its listeners.

     */

    public synchronized void endUpdate() {

        updateLevel--;

        if (updateLevel == 0) {

            compoundEdit.end();

            _postEdit(compoundEdit);

            compoundEdit = null;

        }

    }

    /**

     * Returns a string that displays and identifies this

     * object's properties.

     *

     * @return a <code>String</code> representation of this object

     */

    public String toString() {

        return super.toString() +

            " updateLevel: " + updateLevel +

            " listeners: " + listeners +

            " compoundEdit: " + compoundEdit;

    }

}