001/* AbstractUndoableEdit.java -- 002 Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package javax.swing.undo; 040 041import java.io.Serializable; 042 043import javax.swing.UIManager; 044 045/** 046 * A default implementation of <code>UndoableEdit</code> that can be 047 * used as a base for implementing editing operations. 048 * 049 * @author Andrew Selkirk (aselkirk@sympatico.ca) 050 * @author Sascha Brawer (brawer@dandelis.ch) 051 */ 052public class AbstractUndoableEdit 053 implements UndoableEdit, Serializable 054{ 055 /** 056 * The serialization ID. Verified using the <code>serialver</code> 057 * tool of Apple/Sun JDK 1.3.1 on MacOS X 10.1.5, and Sun JDK 058 * 1.4.1_01 on GNU/Linux. 059 */ 060 static final long serialVersionUID = 580150227676302096L; 061 062 063 /** 064 * The constant string “Undo”, which was returned by 065 * {@link #getUndoPresentationName()} on early versions of the 066 * platform. However, this field has become obsolete with version 067 * 1.3.1. That method now retrieves a localized string from the 068 * {@link javax.swing.UIManager}, using the key 069 * <code>“AbstractUndoableEdit.undoText”</code>. 070 */ 071 protected static final String UndoName = "Undo"; 072 073 074 /** 075 * The constant string “Redo”, which was returned by 076 * {@link #getRedoPresentationName()} on early versions of the 077 * platform. However, this field has become obsolete with version 078 * 1.3.1. That method now retrieves a localized string from the 079 * {@link javax.swing.UIManager}, using the key 080 * <code>“AbstractUndoableEdit.redoText”</code>. 081 */ 082 protected static final String RedoName = "Redo"; 083 084 085 /** 086 * Indicates whether this editing action has been executed. A value 087 * of <code>true</code> means that the action was performed, or that 088 * a redo operation was successful. A value of <code>false</code> 089 * means that the action has not yet performed, or that an undo 090 * operation was successful. 091 */ 092 private boolean hasBeenDone; 093 094 095 /** 096 * Indicates whether this editing action is still alive. The value 097 * is set to <code>true</code> by the constructor, and to 098 * <code>false</code> by the {@link #die()} method. 099 */ 100 private boolean alive; 101 102 103 /** 104 * Constructs a new <code>AbstractUndoableEdit</code>. The initial 105 * state is that the editing action is alive, and 106 * <code>hasBeenDone</code> is <code>true</code>. 107 */ 108 public AbstractUndoableEdit() 109 { 110 // The API specification is not clear, but Mauve test code has 111 // determined that hasBeenDone is initially set to true. 112 alive = hasBeenDone = true; 113 } 114 115 116 /** 117 * Undoes this editing action. 118 * 119 * @throws CannotUndoException if {@link #canUndo()} returns 120 * <code>false</code>, for example because this action has already 121 * been undone. 122 * 123 * @see #canUndo() 124 * @see #redo() 125 */ 126 public void undo() 127 throws CannotUndoException 128 { 129 if (!canUndo()) 130 throw new CannotUndoException(); 131 hasBeenDone = false; 132 } 133 134 135 /** 136 * Determines whether it would be possible to undo this editing 137 * action. 138 * 139 * @return <code>true</code> to indicate that this action can be 140 * undone, <code>false</code> otherwise. 141 * 142 * @see #undo() 143 * @see #canRedo() 144 */ 145 public boolean canUndo() 146 { 147 return alive && hasBeenDone; 148 } 149 150 151 /** 152 * Redoes this editing action. 153 * 154 * @throws CannotRedoException if {@link #canRedo()} returns 155 * <code>false</code>, for example because this action has not 156 * yet been undone. 157 * 158 * @see #canRedo() 159 * @see #undo() 160 */ 161 public void redo() 162 throws CannotRedoException 163 { 164 if (!canRedo()) 165 throw new CannotRedoException(); 166 hasBeenDone = true; 167 } 168 169 170 /** 171 * Determines whether it would be possible to redo this editing 172 * action. 173 * 174 * @return <code>true</code> to indicate that this action can be 175 * redone, <code>false</code> otherwise. 176 * 177 * @see #redo() 178 * @see #canUndo() 179 */ 180 public boolean canRedo() 181 { 182 return alive && !hasBeenDone; 183 } 184 185 186 /** 187 * Informs this edit action that it will no longer be used. Some 188 * actions might use this information to release resources, for 189 * example open files. Called by {@link UndoManager} before this 190 * action is removed from the edit queue. 191 */ 192 public void die() 193 { 194 alive = false; 195 } 196 197 198 /** 199 * Incorporates another editing action into this one, thus forming a 200 * combined action. 201 * 202 * <p>The default implementation always returns <code>false</code>, 203 * indicating that the editing action could not be incorporated. 204 * 205 * @param edit the editing action to be incorporated. 206 */ 207 public boolean addEdit(UndoableEdit edit) 208 { 209 return false; 210 } 211 212 213 /** 214 * Incorporates another editing action into this one, thus forming a 215 * combined action that replaces the argument action. 216 * 217 * <p>The default implementation always returns <code>false</code>, 218 * indicating that the argument action should not be replaced. 219 * 220 * @param edit the editing action to be replaced. 221 */ 222 public boolean replaceEdit(UndoableEdit edit) 223 { 224 return false; 225 } 226 227 228 /** 229 * Determines whether this editing action is significant enough for 230 * being seperately undoable by the user. A typical significant 231 * action would be the resizing of an object. However, changing the 232 * selection in a text document would usually not be considered 233 * significant. 234 * 235 * <p>The default implementation returns <code>true</code>. 236 * 237 * @return <code>true</code> to indicate that the action is 238 * significant enough for being separately undoable, or 239 * <code>false</code> otherwise. 240 */ 241 public boolean isSignificant() 242 { 243 return true; 244 } 245 246 247 /** 248 * Returns a human-readable, localized name that describes this 249 * editing action and can be displayed to the user. 250 * 251 * <p>The default implementation returns an empty string. 252 */ 253 public String getPresentationName() 254 { 255 return ""; 256 } 257 258 259 /** 260 * Calculates a localized name for presenting the undo action to the 261 * user. 262 * 263 * <p>The default implementation returns the concatenation of the 264 * string “Undo” and the action name, which is 265 * determined by calling {@link #getPresentationName()}. 266 * 267 * <p>The string “Undo” is retrieved from the {@link 268 * javax.swing.UIManager}, using the key 269 * <code>“AbstractUndoableEdit.undoText”</code>. This 270 * allows the text to be localized. 271 */ 272 public String getUndoPresentationName() 273 { 274 String msg, pres; 275 276 msg = UIManager.getString("AbstractUndoableEdit.undoText"); 277 if (msg == null) 278 msg = UndoName; 279 280 pres = getPresentationName(); 281 if ((pres == null) || (pres.length() == 0)) 282 return msg; 283 else 284 return msg + ' ' + pres; 285 } 286 287 288 /** 289 * Calculates a localized name for presenting the redo action to the 290 * user. 291 * 292 * <p>The default implementation returns the concatenation of the 293 * string “Redo” and the action name, which is 294 * determined by calling {@link #getPresentationName()}. 295 * 296 * <p>The string “Redo” is retrieved from the {@link 297 * javax.swing.UIManager}, using the key 298 * <code>“AbstractUndoableEdit.redoText”</code>. This 299 * allows the text to be localized. 300 */ 301 public String getRedoPresentationName() 302 { 303 String msg, pres; 304 305 msg = UIManager.getString("AbstractUndoableEdit.redoText"); 306 if (msg == null) 307 msg = RedoName; 308 309 pres = getPresentationName(); 310 if ((pres == null) || (pres.length() == 0)) 311 return msg; 312 else 313 return msg + ' ' + pres; 314 } 315 316 317 public String toString() 318 { 319 return super.toString() 320 + " hasBeenDone: " + hasBeenDone 321 + " alive: " + alive; 322 } 323}