Chip 1998 November/Chip_1998-11_cd.bin/tema/Cafe/jfc.bin/AbstractUndoableEdit.java

Text File | 1998-02-26 | 5KB | 209 lines

/*
 * @(#)AbstractUndoableEdit.java    1.9 97/08/15
 *
 * Copyright (c) 1997 Sun Microsystems, Inc. All Rights Reserved.
 *
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 *
 */

package com.sun.java.swing.undo;

/**
 * An abstract implementation of UndoableEdit, implementing simple
 * responses to all boolean methods in that interface.
 */
public class AbstractUndoableEdit implements UndoableEdit {

    /**
     * String returned by getUndoPresentationName()
     */
    protected static final String UndoName = "Undo";    // PENDING(rjrjr): these need

    /**
     * String returned by getRedoPresentationName()
     */
    protected static final String RedoName = "Redo";    // to be localizable

    /**
     * Defaults to true. Becomes false if this edit is undone, true
     * again if it is redone.
     */
    boolean hasBeenDone;

    /**
     * True if this edit has not received die().
     */
    boolean alive;

    public AbstractUndoableEdit() {
    super();

    hasBeenDone = true;
    alive = true;
    }

    /**
     * Sets alive to false. Note that this is a one way operation:
     * dead edits cannot be resurrected.  Sending undo() or redo() to
     * a dead edit results in an exception being thrown.
     *
     * Typically an edit is killed when it is consolidated by another
     * edit's addEdit() or replaceEdit() method, or when it is
     * dequeued from an UndoManager
     */
    public void die() {
    alive = false;
    }

    /**
     * Throws CannotUndoException if canUndo() returns false. Sets
     * hasBeenDone to false. Subclasses should override to undo the
     * operation represented by this edit. Override should begin with
     * a call to super.
     *
     * @see    #canUndo
     */
    public void undo() throws CannotUndoException {
    if (!canUndo()) {
        throw new CannotUndoException();
    }
    hasBeenDone = false;
    }

    /**
     * Returns true if this edit is alive and hasBeenDone is true.
     *
     * @see     #die
     * @see    #undo
     * @see    #redo
     */
    public boolean canUndo() {
    return alive && hasBeenDone;
    }

    /**
     * Throws CannotRedoException if canRedo() returns false. Sets
     * hasBeenDone to true. Subclasses should override to redo the
     * operation represented by this edit. Override should begin with
     * a call to super.
     *
     * @see    #canRedo
     */
    public void redo() throws CannotRedoException {
    if (!canRedo()) {
        throw new CannotRedoException();
    }
    hasBeenDone = true;
    }

    /**
     * Returns true if this edit is alive and hasBeenDone is false.
     *
     * @see     #die
     * @see    #undo
     * @see    #redo
     */
    public boolean canRedo() {
    return alive && !hasBeenDone;
    }

    /**
     * This default implementation returns false.
     *
     * @see UndoableEdit#addEdit
     */
    public boolean addEdit(UndoableEdit anEdit) {
    return false;
    }

    /**
     * This default implementation returns false.
     *
     * @see UndoableEdit#replaceEdit
     */
    public boolean replaceEdit(UndoableEdit anEdit) {
    return false;
    }

    /**
     * This default implementation returns true.
     *
     * @see UndoableEdit#isSignificant
     */
    public boolean isSignificant() {
    return true;
    }

    /**
     * This default implementation returns "". Used by
     * getUndoPresentationName() and getRedoPresentationName() to
     * construct the strings they return. Subclasses shoul override to
     * return an appropriate description of the operation this edit
     * represents.
     *
     * @see    #getUndoPresentationName
     * @see    #getRedoPresentationName
     */
    public String getPresentationName() {
    return "";
    }

    /**
     * If getPresentationName() returns "", returns
     * AbstractUndoableEdit.UndoName. Otherwise returns
     * AbstractUndoableEdit.UndoName followed by a space and
     * getPresentationName()
     *
     * @see #getPresentationName
     */
    public String getUndoPresentationName() {
    String name = getPresentationName();
    if (name != "") {
        name = UndoName + " " + name;
    } else {
        name = UndoName;
    }

    return name;
    }

    /**
     * If getPresentationName() returns "", returns
     * AbstractUndoableEdit.RedoName. Otherwise returns
     * AbstractUndoableEdit.RedoName followed by a space and
     * getPresentationName()
     *
     * @see #getPresentationName
     */
    public String getRedoPresentationName() {
    String name = getPresentationName();
    if (name != "") {
        name = RedoName + " " + name;
    } else {
        name = RedoName;
    }

    return name;
    }

    public String toString()
    {
    return super.toString()
        + " hasBeenDone: " + hasBeenDone
        + " alive: " + alive;
    }
}