undomanager.java

gcc的组建

   * @param edit the last editing action to be undone.
   */
  protected void undoTo(UndoableEdit edit)
    throws CannotUndoException
  {
    UndoableEdit cur;

    if (!edits.contains(edit))
      throw new CannotUndoException();

    while (true)
      {
        indexOfNextAdd -= 1;
        cur = (UndoableEdit) edits.get(indexOfNextAdd);
        cur.undo();
        if (cur == edit)
          return;
      }
  }


  /**
   * Redoes all editing actions in the same order as they were
   * added to this UndoManager, up to the specified action.
   *
   * @param edit the last editing action to be redone.
   */
  protected void redoTo(UndoableEdit edit)
    throws CannotRedoException
  {
    UndoableEdit cur;

    if (!edits.contains(edit))
      throw new CannotRedoException();

    while (true)
      {
        cur = (UndoableEdit) edits.get(indexOfNextAdd);
        indexOfNextAdd += 1;
        cur.redo();
        if (cur == edit)
          return;
      }
  }

  
  /**
   * Undoes or redoes the last action. If the last action has already
   * been undone, it will be re-done, and vice versa.
   *
   * <p>This is useful for applications that do not present a separate
   * undo and redo facility, but just have a single menu item for
   * undoing and redoing the very last action. Such applications will
   * use an <code>UndoManager</code> whose <code>limit</code> is 1.
   */
  public synchronized void undoOrRedo()
    throws CannotRedoException, CannotUndoException
  {
    if (indexOfNextAdd == edits.size())
      undo();
    else
      redo();
  }


  /**
   * Determines whether it would be possible to either undo or redo
   * this editing action.
   *
   * <p>This is useful for applications that do not present a separate
   * undo and redo facility, but just have a single menu item for
   * undoing and redoing the very last action. Such applications will
   * use an <code>UndoManager</code> whose <code>limit</code> is 1.
   *
   * @return <code>true</code> to indicate that this action can be
   * undone or redone; <code>false</code> if neither is possible at
   * the current time.
   */
  public synchronized boolean canUndoOrRedo()
  {
    return indexOfNextAdd == edits.size() ? canUndo() : canRedo();
  }


  /**
   * Undoes one significant edit action. If insignificant actions have
   * been posted after the last signficant action, the insignificant
   * ones will be undone first.
   *
   * <p>However, if {@link #end()} has been called on this
   * UndoManager, it will behave like a normal {@link
   * CompoundEdit}. In this case, all actions will be undone in
   * reverse order of addition. Typical applications will never call
   * {@link #end()} on their <code>UndoManager</code>.
   *
   * @throws CannotUndoException if no action can be undone.
   *
   * @see #canUndo()
   * @see #redo()
   * @see #undoOrRedo()
   */
  public synchronized void undo()
    throws CannotUndoException
  {
    if (!isInProgress())
      {
        super.undo();
        return;
      }

    UndoableEdit edit = editToBeUndone();
    if (edit == null)
      throw new CannotUndoException();

    undoTo(edit);
  }


  /**
   * Determines whether it would be possible to undo this editing
   * action.
   *
   * @return <code>true</code> to indicate that this action can be
   * undone; <code>false</code> otherwise.
   *
   * @see #undo()
   * @see #canRedo()
   * @see #canUndoOrRedo()
   */
  public synchronized boolean canUndo()
  {
    UndoableEdit edit;

    if (!isInProgress())
      return super.canUndo();

    edit = editToBeUndone();
    return edit != null && edit.canUndo();
  }



  /**
   * Redoes one significant edit action. If insignificant actions have
   * been posted in between, the insignificant ones will be redone
   * first.
   *
   * <p>However, if {@link #end()} has been called on this
   * UndoManager, it will behave like a normal {@link
   * CompoundEdit}. In this case, <em>all</em> actions will be redone
   * in order of addition. Typical applications will never call {@link
   * #end()} on their <code>UndoManager</code>.
   *
   * @throws CannotRedoException if no action can be redone.
   *
   * @see #canRedo()
   * @see #redo()
   * @see #undoOrRedo()
   */
  public synchronized void redo()
    throws CannotRedoException
  {
    if (!isInProgress())
      {
        super.redo();
        return;
      }

    UndoableEdit edit = editToBeRedone();
    if (edit == null)
      throw new CannotRedoException();

    redoTo(edit);
  }


  /**
   * Determines whether it would be possible to redo this editing
   * action.
   *
   * @return <code>true</code> to indicate that this action can be
   * redone; <code>false</code> otherwise.
   *
   * @see #redo()
   * @see #canUndo()
   * @see #canUndoOrRedo()
   */
  public synchronized boolean canRedo()
  {
    UndoableEdit edit;

    if (!isInProgress())
      return super.canRedo();

    edit = editToBeRedone();
    return edit != null && edit.canRedo();
  }


  /**
   * Registers an undoable editing action with this UndoManager.  If
   * the capacity <code>limit</code> is reached, the oldest action
   * will be discarded (and receives a {@linkplain UndoableEdit#die()
   * die message}. Equally, any actions that were undone (but not re-done)
   * will be discarded, too.
   *
   * @param edit the editing action that is added to this UndoManager.
   *
   * @return <code>true</code> if <code>edit</code> could be
   * incorporated; <code>false</code> if <code>edit</code> has not
   * been incorporated because {@link #end()} has already been called
   * on this <code>UndoManager</code>.
   */
  public synchronized boolean addEdit(UndoableEdit edit)
  {
    boolean result;

    // Discard any edits starting at indexOfNextAdd.
    trimEdits(indexOfNextAdd, edits.size() - 1);

    result = super.addEdit(edit);
    indexOfNextAdd = edits.size();
    trimForLimit();
    return result;
  }


  /**
   * Calculates a localized text for presenting the undo or redo
   * action to the user, for example in the form of a menu command.
   *
   * <p>This is useful for applications that do not present a separate
   * undo and redo facility, but just have a single menu item for
   * undoing and redoing the very last action. Such applications will
   * use an <code>UndoManager</code> whose <code>limit</code> is 1.
   *
   * @return the redo presentation name if the last action has already
   * been undone, or the undo presentation name otherwise.
   *
   * @see #getUndoPresentationName()
   * @see #getRedoPresentationName()
   */
  public synchronized String getUndoOrRedoPresentationName()
  {
    if (indexOfNextAdd == edits.size())
      return getUndoPresentationName();
    else
      return getRedoPresentationName();
  }


  /**
   * Calculates a localized text for presenting the undo action
   * to the user, for example in the form of a menu command.
   */
  public synchronized String getUndoPresentationName()
  {
    UndoableEdit edit;

    if (!isInProgress())
      return super.getUndoPresentationName();

    edit = editToBeUndone();
    if (edit == null)
      return UIManager.getString("AbstractUndoableEdit.undoText");
    else
      return edit.getUndoPresentationName();
  }


  /**
   * Calculates a localized text for presenting the redo action
   * to the user, for example in the form of a menu command.
   */
  public synchronized String getRedoPresentationName()
  {
    UndoableEdit edit;

    if (!isInProgress())
      return super.getRedoPresentationName();

    edit = editToBeRedone();
    if (edit == null)
      return UIManager.getString("AbstractUndoableEdit.redoText");
    else
      return edit.getRedoPresentationName();
  }
  
  
  /**
   * Registers the edit action of an {@link UndoableEditEvent}
   * with this UndoManager.
   *
   * <p><b>Thread Safety:</b> This method may safely be invoked from
   * concurrent threads.  The caller does not need to perform external
   * synchronization. This means that {@link
   * javax.swing.event.UndoableEditEvent} sources do not need to broadcast
   * their events from inside the Swing worker thread.
   *
   * @param event the event whose <code>edit</code> will be
   * passed to {@link #addEdit}.
   *
   * @see UndoableEditEvent#getEdit()
   * @see #addEdit
   */
  public void undoableEditHappened(UndoableEditEvent event)
  {
    // Note that this method does not need to be synchronized,
    // because addEdit will obtain and release the mutex.
    addEdit(event.getEdit());
  }
}