swing/undo/CompoundEdit.java

/* CompoundEdit.java -- Combines multiple UndoableEdits.
   Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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permission to link this library with independent modules to produce an
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package javax.swing.undo;

import java.util.Vector;

/**
 * An editing action that consists of multiple
 * <code>UndoableEdits</code>.
 *
 * <p>The use of a <code>CompoundEdit</code> is divided in two separate
 * phases.
 *
 * <ol><li>In the first phase, the <code>CompoundEdit</code> is
 * initialized.  After a new instance of <code>CompoundEdit</code> has
 * been created, {@link #addEdit(UndoableEdit)} is called for each
 * element of the compound.  To terminate the initialization phase,
 * call {@link #end()}.</li>
 *
 * <li>In the second phase, the the <code>CompoundEdit</code> can be
 * used, typically by invoking {@link #undo()} and {@link
 * #redo()}.</li></ol>
 *
 * @author Andrew Selkirk (aselkirk@sympatico.ca)
 * @author Sascha Brawer (brawer@dandelis.ch)
 */
public class CompoundEdit
  extends AbstractUndoableEdit
{
  /**
   * The identifier of this class in object serialization. Determined
   * using the serialver tool of Sun J2SE 1.4.1_01.
   */
  private static final long serialVersionUID = -6512679249930119683L;


  /**
   * The <code>UndoableEdit</code>s being combined into a compound
   * editing action.
   */
  protected Vector edits;


  /**
   * Indicates whether the creation of this CompoundEdit is still in
   * progress. Initially, the value of this flag is
   * <code>true</code>. The {@link #end()} method changes the flag to
   * <code>false</code>.
   */
  private boolean inProgress;


  /**
   * Constructs a new CompoundEdit.
   */
  public CompoundEdit()
  {
    edits = new Vector();
    inProgress = true;
  }


  /**
   * Undoes all edits that are part of of this
   * <code>CompoundEdit</code>. The compound elements will receive the
   * <code>undo</code> message in the reverse order of addition.
   *
   * @throws CannotUndoException if {@link #canUndo()} returns
   * <code>false</code>. This can happen if {@link #end()} has not
   * been called on this <code>CompoundEdit</code>, or if this edit
   * has already been undone.
   *
   * @see #canUndo()
   * @see #redo()
   */
  public void undo()
    throws CannotUndoException
  {
    // AbstractUndoableEdit.undo() will throw a CannotUndoException if
    // canUndo returns false.
    super.undo();

    for (int i = edits.size() - 1; i >= 0; i--)
      ((UndoableEdit) edits.elementAt(i)).undo();
  }


  /**
   * Redoes all edits that are part of of this
   * <code>CompoundEdit</code>. The compound elements will receive the
   * <code>undo</code> message in the same order as they were added.
   *
   * @throws CannotRedoException if {@link #canRedo()} returns
   * <code>false</code>. This can happen if {@link #end()} has not
   * been called on this <code>CompoundEdit</code>, or if this edit
   * has already been redone.
   *
   * @see #canRedo()
   * @see #undo()
   */
  public void redo()
    throws CannotRedoException
  {
    // AbstractUndoableEdit.redo() will throw a CannotRedoException if
    // canRedo returns false.
    super.redo();

    for (int i = 0; i < edits.size(); i++)
      ((UndoableEdit) edits.elementAt(i)).redo();
  }


  /**
   * Returns the the <code>UndoableEdit</code> that was last added to
   * this compound.
   */
  protected UndoableEdit lastEdit()
  {
    if (edits.size() == 0)
      return null;
    else
      return (UndoableEdit) edits.elementAt(edits.size() - 1);
  }


  /**
   * Informs this edit action, and all compound edits, that they will
   * no longer be used. Some actions might use this information to
   * release resources such as open files.  Called by {@link
   * UndoManager} before this action is removed from the edit queue.
   *
   * <p>The compound elements will receive the
   * <code>die</code> message in the reverse order of addition.
   */
  public void die()
  {
    for (int i = edits.size() - 1; i >= 0; i--)
      ((UndoableEdit) edits.elementAt(i)).die();

    super.die();
  }


  /**
   * Incorporates another editing action into this one, thus forming a
   * combined edit.
   *
   * <p>If this edit&#x2019;s {@link #end()} method has been called
   * before, <code>false</code> is returned immediately. Otherwise,
   * the {@linkplain #lastEdit() last added edit} is given the
   * opportunity to {@linkplain UndoableEdit#addEdit(UndoableEdit)
   * incorporate} <code>edit</code>.  If this fails, <code>edit</code>
   * is given the opportunity to {@linkplain
   * UndoableEdit#replaceEdit(UndoableEdit) replace} the last added
   * edit.  If this fails as well, <code>edit</code> gets added as a
   * new compound to {@link #edits}.
   *
   * @param edit the editing action being added.
   *
   * @return <code>true</code> if <code>edit</code> could somehow be
   * incorporated; <code>false</code> if <code>edit</code> has not
   * been incorporated because {@link #end()} was called before.
   */
  public boolean addEdit(UndoableEdit edit)
  {
    UndoableEdit last;

    // If end has been called before, do nothing.
    if (!inProgress)
      return false;

    last = lastEdit();

    // If edit is the very first edit, just add it to the list.
    if (last == null)
    {
      edits.add(edit);
      return true;
    }

    // Try to incorporate edit into last.
    if (last.addEdit(edit))
      return true;

    // Try to replace last by edit.
    if (edit.replaceEdit(last))
    {
      edits.set(edits.size() - 1, edit);
      return true;
    }

    // If everything else has failed, add edit to the list of compound
    // edits.
    edits.add(edit);
    return true;
  }


  /**
   * Informs this <code>CompoundEdit</code> that its construction
   * phase has been completed. After this method has been called,
   * {@link #undo()} and {@link #redo()} may be called, {@link
   * #isInProgress()} will return <code>false</code>, and all attempts
   * to {@linkplain #addEdit(UndoableEdit) add further edits} will
   * fail.
   */
  public void end()
  {
    inProgress = false;
  }


  /**
   * Determines whether it would be possible to undo this editing
   * action. The result will be <code>true</code> if {@link #end()}
   * has been called on this <code>CompoundEdit</code>, {@link #die()}
   * has not yet been called, and the edit has not been undone
   * already.
   *
   * @return <code>true</code> to indicate that this action can be
   * undone; <code>false</code> otherwise.
   *
   * @see #undo()
   * @see #canRedo()
   */
  public boolean canUndo()
  {
    return !inProgress && super.canUndo();
  }


  /**
   * Determines whether it would be possible to redo this editing
   * action. The result will be <code>true</code> if {@link #end()}
   * has been called on this <code>CompoundEdit</code>, {@link #die()}
   * has not yet been called, and the edit has not been redone
   * already.
   *
   * @return <code>true</code> to indicate that this action can be
   * redone; <code>false</code> otherwise.
   *
   * @see #redo()
   * @see #canUndo()
   */
  public boolean canRedo()
  {
    return !inProgress && super.canRedo();
  }


  /**
   * Determines whether the initial construction phase of this
   * <code>CompoundEdit</code> is still in progress.  During this
   * phase, edits {@linkplain #addEdit(UndoableEdit) may be
   * added}. After initialization has been terminated by calling
   * {@link #end()}, {@link #undo()} and {@link #redo()} can be used.
   *
   * @return <code>true</code> if the initialization phase is still in
   * progress; <code>false</code> if {@link #end()} has been called.
   *
   * @see #end()
   */
  public boolean isInProgress()
  {
    return inProgress;
  }


  /**
   * Determines whether this editing action is significant enough for
   * being seperately undoable by the user. A typical significant
   * action would be the resizing of an object. However, changing the
   * selection in a text document would usually not be considered
   * significant.
   *
   * <p>A <code>CompoundEdit</code> is significant if any of its
   * elements are significant.
   */
  public boolean isSignificant()
  {
    for (int i = edits.size() - 1; i >= 0; i--)
      if (((UndoableEdit) edits.elementAt(i)).isSignificant())
        return true;

    return false;
  }


  /**
   * Returns a human-readable, localized name that describes this
   * editing action and can be displayed to the user.
   *
   * <p>The implementation delegates the call to the {@linkplain
   * #lastEdit() last added edit action}. If no edit has been added
   * yet, the inherited implementation will be invoked, which always
   * returns an empty string.
   */
  public String getPresentationName()
  {
    UndoableEdit last;

    last = lastEdit();
    if (last == null)
      return super.getPresentationName();
    else
      return last.getPresentationName();
  }


  /**
   * Calculates a localized message text for presenting the undo
   * action to the user.
   *
   * <p>The implementation delegates the call to the {@linkplain
   * #lastEdit() last added edit action}. If no edit has been added
   * yet, the {@linkplain
   * AbstractUndoableEdit#getUndoPresentationName() inherited
   * implementation} will be invoked.
   */
  public String getUndoPresentationName()
  {
    UndoableEdit last;

    last = lastEdit();
    if (last == null)
      return super.getUndoPresentationName();
    else
      return last.getUndoPresentationName();
  }


  /**
   * Calculates a localized message text for presenting the redo
   * action to the user.
   *
   * <p>The implementation delegates the call to the {@linkplain
   * #lastEdit() last added edit action}. If no edit has been added
   * yet, the {@linkplain
   * AbstractUndoableEdit#getRedoPresentationName() inherited
   * implementation} will be invoked.
   */
  public String getRedoPresentationName()
  {
    UndoableEdit last;

    last = lastEdit();
    if (last == null)
      return super.getRedoPresentationName();
    else
      return last.getRedoPresentationName();
  }


  /**
   * Calculates a string that may be useful for debugging.
   */
  public String toString()
  {
    return super.toString()
      + " inProgress: " + inProgress
      + " edits: " + edits;
  }
}