UndoableEdit


1   /*
2    * @(#)UndoableEdit.java    1.19 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.swing.undo;
9   
10  import javax.swing.event.*;
11  
12  /**
13   * An object representing an edit that has been done, and that can be
14   * undone and redone.
15   *
16   * @version 1.19, 12/19/03
17   * @author Ray Ryan
18   */
19  
20  public interface UndoableEdit {
21      /**
22       * Undo the edit that was made.
23       */
24      public void undo() throws CannotUndoException  ;
25  
26      /**
27       * True if it is still possible to undo this operation.
28       */
29      public boolean canUndo();
30  
31      /**
32       * Re-apply the edit, assuming that it has been undone.
33       */
34      public void redo() throws CannotRedoException  ;
35  
36      /**
37       * True if it is still possible to redo this operation.
38       */
39      public boolean canRedo();
40  
41      /**
42       * May be sent to inform an edit that it should no longer be
43       * used. This is a useful hook for cleaning up state no longer
44       * needed once undoing or redoing is impossible--for example,
45       * deleting file resources used by objects that can no longer be
46       * undeleted. <code>UndoManager</code> calls this before it dequeues edits.
47       *
48       * Note that this is a one-way operation. There is no "un-die"
49       * method.
50       *
51       * @see CompoundEdit#die
52       */
53      public void die();
54  
55      /**
56       * This <code>UndoableEdit</code> should absorb <code>anEdit</code>
57       * if it can. Returns true
58       * if <code.anEdit</code> has been incorporated, false if it has not.
59       *
60       * <p>Typically the receiver is already in the queue of a
61       * <code>UndoManager</code> (or other <code>UndoableEditListener</code>),
62       * and is being given a chance to incorporate <code>anEdit</code>
63       * rather than letting it be added to the queue in turn.</p>
64       *
65       * <p>If true is returned, from now on <code>anEdit</code> must return
66       * false from <code>canUndo</code> and <code>canRedo</code>,
67       * and must throw the appropriate exception on <code>undo</code> or
68       * <code>redo</code>.</p>
69       * @param anEdit the edit to be added
70       */
71      public boolean addEdit(UndoableEdit   anEdit);
72  
73      /**
74       * Returns true if this <code>UndoableEdit</code> should replace
75       * <code>anEdit</code>. The receiver should incorporate
76       * <code>anEdit</code>'s state before returning true.
77       *
78       * <p>This message is the opposite of addEdit--anEdit has typically
79       * already been queued in a <code>UndoManager</code> (or other
80       * UndoableEditListener), and the receiver is being given a chance
81       * to take its place.</p>
82       *
83       * <p>If true is returned, from now on anEdit must return false from
84       * canUndo() and canRedo(), and must throw the appropriate
85       * exception on undo() or redo().</p>
86       */
87      public boolean replaceEdit(UndoableEdit   anEdit);
88  
89      /**
90       * Returns false if this edit is insignificant--for example one
91       * that maintains the user's selection, but does not change any
92       * model state. This status can be used by an 
93       * <code>UndoableEditListener</code>
94       * (like UndoManager) when deciding which UndoableEdits to present
95       * to the user as Undo/Redo options, and which to perform as side
96       * effects of undoing or redoing other events.
97       */
98      public boolean isSignificant();
99  
100     /**
101      * Provides a localized, human readable description of this edit
102      * suitable for use in, say, a change log.
103      */
104     public String   getPresentationName();
105 
106     /**
107      * Provides a localized, human readable description of the undoable
108      * form of this edit, e.g. for use as an Undo menu item. Typically
109      * derived from <code>getDescription</code>.
110      */
111     public String   getUndoPresentationName();
112 
113     /**
114      * Provides a localized, human readable description of the redoable
115      * form of this edit, e.g. for use as a Redo menu item. Typically
116      * derived from <code>getPresentationName</code>.
117      */
118     public String   getRedoPresentationName();
119 }
120
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