chargerlib.undo

Class UndoStateManager

Object

chargerlib.undo.UndoStateManager

public class UndoStateManager
extends Object

Manages the saving and restoring of states. This manager relies on the implementer to decide the granularity of undoing things. markAfterUndoableStep should be called AFTER some atomic action that is undoable. resetAndMark is a good thing to call at the beginning of a session, or when contents have been saved to a file, or any other situation where it is no longer necessary to maintain the history of actions for un-doing.

What constitutes a state is entirely the responsibility of the implementer of the Undoable interface. As much or as little of the object's state may be saved/restored as required by the application's interaction.

Since:

Charger 3.8.3

See Also:

UndoableState, Undoable

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	enabled Whether to actually operate or not
Undoable	stateSource The object whose states are being managed.
protected UndoRedoList<UndoableState>	urStack Supports the undo/redo operations.

Constructor Summary

Constructors

Constructor and Description
UndoStateManager(Undoable source, int max) Instantiates the manager, with an undo/redo maximum level.

Method Summary

Modifier and Type	Method and Description
void	doRedo() Restores the object's state from the state just forward of the current one.
void	doUndo() Restores the object's state from the last saved state.
boolean	isEnabled() Whether this manager is enabled or not.
void	markAfterUndoableStep() Tells the state manager that we've just completed something undoable.
boolean	redoAvailable() Is there a future state to restore?
void	reset() Empties the undo redo lists.
void	resetAndMark() Forget all previous actions and mark the current state for further possible undo.
void	setEnabled(boolean enabled) Disable the marking capability.
boolean	undoAvailable() Is there any previous state to restore?

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

urStack

protected UndoRedoList<UndoableState> urStack

Supports the undo/redo operations. Should be protected, but we often need to display it for debugging.

stateSource

public Undoable stateSource

The object whose states are being managed.

enabled

protected boolean enabled

Whether to actually operate or not

Constructor Detail

UndoStateManager

public UndoStateManager(Undoable source,
                        int max)

Instantiates the manager, with an undo/redo maximum level.

Parameters:

max - the most number of previous/future actions handled by "undo" If max is reached, then old states are discarded.

Method Detail

markAfterUndoableStep

public void markAfterUndoableStep()

Tells the state manager that we've just completed something undoable.

doUndo

public void doUndo()

Restores the object's state from the last saved state. Leaves the current state as a possible redo target. Disables this manager during the restore state operation.

doRedo

public void doRedo()

Restores the object's state from the state just forward of the current one. Undoes the "undo" process, for one state only. Disables this manager during the restore state operation.

undoAvailable

public boolean undoAvailable()

Is there any previous state to restore?

Returns:

true if we can safely perform an undo, false otherwise

redoAvailable

public boolean redoAvailable()

Is there a future state to restore?

Returns:

true if we can safely perform an redo, false otherwise

reset

public void reset()

Empties the undo redo lists. Not very useful by itself because it usually must be followed by a markAfterUndoableStep with a current state. It is useful when maintaining multiple editing environments to forget all previous actions.

resetAndMark

public void resetAndMark()

Forget all previous actions and mark the current state for further possible undo. This is usually what the programmer wants, since resetting by itself really empties everything.

setEnabled

public void setEnabled(boolean enabled)

Disable the marking capability. This is useful if you're performing some automatic operation that might trigger normally-undoable changes. The actual undo and redo operations are also enabled. In other words, it protects the undo/redo stack from changes.

isEnabled

public boolean isEnabled()

Whether this manager is enabled or not.

Returns:

true if undo/redo states are being marked, false otherwise.