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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package javax.swing.undo;
import javax.swing.event.*;
/**
* An UndoableEdit
represents an edit. The edit may
* be undone, or if already undone the edit may be redone.
*
* UndoableEdit
is designed to be used with the
* UndoManager
. As UndoableEdit
s are generated
* by an UndoableEditListener
they are typically added to
* the UndoManager
. When an UndoableEdit
* is added to an UndoManager
the following occurs (assuming
* end
has not been called on the UndoManager
):
*
UndoManager
contains edits it will call
* addEdit
on the current edit passing in the new edit
* as the argument. If addEdit
returns true the
* new edit is assumed to have been incorporated into the current edit and
* the new edit will not be added to the list of current edits.
* Edits can use addEdit
as a way for smaller edits to
* be incorporated into a larger edit and treated as a single edit.
* addEdit
returns false replaceEdit
* is called on the new edit with the current edit passed in as the
* argument. This is the inverse of addEdit
—
* if the new edit returns true from replaceEdit
, the new
* edit replaces the current edit.
* UndoManager
makes use of
* isSignificant
to determine how many edits should be
* undone or redone. The UndoManager
will undo or redo
* all insignificant edits (isSignificant
returns false)
* between the current edit and the last or
* next significant edit. addEdit
and
* replaceEdit
can be used to treat multiple edits as
* a single edit, returning false from isSignificant
* allows for treating can be used to
* have many smaller edits undone or redone at once. Similar functionality
* can also be done using the addEdit
method.
*
* @author Ray Ryan
*/
public interface UndoableEdit {
/**
* Undo the edit.
*
* @throws CannotUndoException if this edit can not be undone
*/
public void undo() throws CannotUndoException;
/**
* Returns true if this edit may be undone.
*
* @return true if this edit may be undone
*/
public boolean canUndo();
/**
* Re-applies the edit.
*
* @throws CannotRedoException if this edit can not be redone
*/
public void redo() throws CannotRedoException;
/**
* Returns true if this edit may be redone.
*
* @return true if this edit may be redone
*/
public boolean canRedo();
/**
* Informs the edit that it should no longer be used. Once an
* UndoableEdit
has been marked as dead it can no longer
* be undone or redone.
*
* This is a useful hook for cleaning up state no longer
* needed once undoing or redoing is impossible--for example,
* deleting file resources used by objects that can no longer be
* undeleted. UndoManager
calls this before it dequeues edits.
*
* Note that this is a one-way operation. There is no "un-die"
* method.
*
* @see CompoundEdit#die
*/
public void die();
/**
* Adds an UndoableEdit
to this UndoableEdit
.
* This method can be used to coalesce smaller edits into a larger
* compound edit. For example, text editors typically allow
* undo operations to apply to words or sentences. The text
* editor may choose to generate edits on each key event, but allow
* those edits to be coalesced into a more user-friendly unit, such as
* a word. In this case, the UndoableEdit
would
* override addEdit
to return true when the edits may
* be coalesced.
*
* A return value of true indicates anEdit
was incorporated
* into this edit. A return value of false indicates anEdit
* may not be incorporated into this edit.
*
Typically the receiver is already in the queue of a
* UndoManager
(or other UndoableEditListener
),
* and is being given a chance to incorporate anEdit
* rather than letting it be added to the queue in turn.
If true is returned, from now on anEdit
must return
* false from canUndo
and canRedo
,
* and must throw the appropriate exception on undo
or
* redo
.
anEdit
may be incorporated into this
* edit
*/
public boolean addEdit(UndoableEdit anEdit);
/**
* Returns true if this UndoableEdit
should replace
* anEdit
. This method is used by CompoundEdit
* and the UndoManager
; it is called if
* anEdit
could not be added to the current edit
* (addEdit
returns false).
* * This method provides a way for an edit to replace an existing edit. *
This message is the opposite of addEdit--anEdit has typically
* already been queued in an UndoManager
(or other
* UndoableEditListener), and the receiver is being given a chance
* to take its place.
If true is returned, from now on anEdit must return false from * canUndo() and canRedo(), and must throw the appropriate * exception on undo() or redo().
* * @param anEdit the edit that replaces the current edit * @return true if this edit should replaceanEdit
*/
public boolean replaceEdit(UndoableEdit anEdit);
/**
* Returns true if this edit is considered significant. A significant
* edit is typically an edit that should be presented to the user, perhaps
* on a menu item or tooltip. The UndoManager
will undo,
* or redo, all insignificant edits to the next significant edit.
*
* @return true if this edit is significant
*/
public boolean isSignificant();
/**
* Returns a localized, human-readable description of this edit, suitable
* for use in a change log, for example.
*
* @return description of this edit
*/
public String getPresentationName();
/**
* Returns a localized, human-readable description of the undoable form of
* this edit, suitable for use as an Undo menu item, for example.
* This is typically derived from getPresentationName
.
*
* @return a description of the undoable form of this edit
*/
public String getUndoPresentationName();
/**
* Returns a localized, human-readable description of the redoable form of
* this edit, suitable for use as a Redo menu item, for example. This is
* typically derived from getPresentationName
.
*
* @return a description of the redoable form of this edit
*/
public String getRedoPresentationName();
}