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UndoManager Class Reference

Manages a list of undo/redo commands. More...

Inherits ChangeBroadcaster.

Public Member Functions

 UndoManager (int maxNumberOfUnitsToKeep=30000, int minimumTransactionsToKeep=30)
 Creates an UndoManager.
 
 ~UndoManager ()
 Destructor.
 
void clearUndoHistory ()
 Deletes all stored actions in the list.
 
int getNumberOfUnitsTakenUpByStoredCommands () const
 Returns the current amount of space to use for storing UndoableAction objects.
 
void setMaxNumberOfStoredUnits (int maxNumberOfUnitsToKeep, int minimumTransactionsToKeep)
 Sets the amount of space that can be used for storing UndoableAction objects.
 
bool perform (UndoableAction *action, const String &actionName=String())
 Performs an action and adds it to the undo history list.
 
void beginNewTransaction (const String &actionName=String())
 Starts a new group of actions that together will be treated as a single transaction.
 
void setCurrentTransactionName (const String &newName)
 Changes the name stored for the current transaction.
 
bool canUndo () const
 Returns true if there's at least one action in the list to undo.
 
String getUndoDescription () const
 Returns the description of the transaction that would be next to get undone.
 
bool undo ()
 Tries to roll-back the last transaction.
 
bool undoCurrentTransactionOnly ()
 Tries to roll-back any actions that were added to the current transaction.
 
void getActionsInCurrentTransaction (Array< const UndoableAction * > &actionsFound) const
 Returns a list of the UndoableAction objects that have been performed during the transaction that is currently open.
 
int getNumActionsInCurrentTransaction () const
 Returns the number of UndoableAction objects that have been performed during the transaction that is currently open.
 
Time getTimeOfUndoTransaction () const
 Returns the time to which the state would be restored if undo() was to be called.
 
Time getTimeOfRedoTransaction () const
 Returns the time to which the state would be restored if redo() was to be called.
 
bool canRedo () const
 Returns true if there's at least one action in the list to redo.
 
String getRedoDescription () const
 Returns the description of the transaction that would be next to get redone.
 
bool redo ()
 Tries to redo the last transaction that was undone.
 
- Public Member Functions inherited from ChangeBroadcaster
 ChangeBroadcaster () noexcept
 Creates an ChangeBroadcaster.
 
virtual ~ChangeBroadcaster ()
 Destructor.
 
void addChangeListener (ChangeListener *listener)
 Registers a listener to receive change callbacks from this broadcaster.
 
void removeChangeListener (ChangeListener *listener)
 Unregisters a listener from the list.
 
void removeAllChangeListeners ()
 Removes all listeners from the list.
 
void sendChangeMessage ()
 Causes an asynchronous change message to be sent to all the registered listeners.
 
void sendSynchronousChangeMessage ()
 Sends a synchronous change message to all the registered listeners.
 
void dispatchPendingMessages ()
 If a change message has been sent but not yet dispatched, this will call sendSynchronousChangeMessage() to make the callback immediately.
 

Detailed Description

Manages a list of undo/redo commands.

An UndoManager object keeps a list of past actions and can use these actions to move backwards and forwards through an undo history.

To use it, create subclasses of UndoableAction which perform all the actions you need, then when you need to actually perform an action, create one and pass it to the UndoManager's perform() method.

The manager also uses the concept of 'transactions' to group the actions together - all actions performed between calls to beginNewTransaction() are grouped together and are all undone/redone as a group.

The UndoManager is a ChangeBroadcaster, so listeners can register to be told when actions are performed or undone.

See Also
UndoableAction

Constructor & Destructor Documentation

UndoManager::UndoManager ( int  maxNumberOfUnitsToKeep = 30000,
int  minimumTransactionsToKeep = 30 
)

Creates an UndoManager.

Parameters
maxNumberOfUnitsToKeepeach UndoableAction object returns a value to indicate how much storage it takes up (UndoableAction::getSizeInUnits()), so this lets you specify the maximum total number of units that the undomanager is allowed to keep in memory before letting the older actions drop off the end of the list.
minimumTransactionsToKeepthis specifies the minimum number of transactions that will be kept, even if this involves exceeding the amount of space specified in maxNumberOfUnitsToKeep
UndoManager::~UndoManager ( )

Destructor.

Member Function Documentation

void UndoManager::clearUndoHistory ( )

Deletes all stored actions in the list.

int UndoManager::getNumberOfUnitsTakenUpByStoredCommands ( ) const

Returns the current amount of space to use for storing UndoableAction objects.

See Also
setMaxNumberOfStoredUnits
void UndoManager::setMaxNumberOfStoredUnits ( int  maxNumberOfUnitsToKeep,
int  minimumTransactionsToKeep 
)

Sets the amount of space that can be used for storing UndoableAction objects.

Parameters
maxNumberOfUnitsToKeepeach UndoableAction object returns a value to indicate how much storage it takes up (UndoableAction::getSizeInUnits()), so this lets you specify the maximum total number of units that the undomanager is allowed to keep in memory before letting the older actions drop off the end of the list.
minimumTransactionsToKeepthis specifies the minimum number of transactions that will be kept, even if this involves exceeding the amount of space specified in maxNumberOfUnitsToKeep
See Also
getNumberOfUnitsTakenUpByStoredCommands
bool UndoManager::perform ( UndoableAction action,
const String actionName = String() 
)

Performs an action and adds it to the undo history list.

Parameters
actionthe action to perform - this will be deleted by the UndoManager when no longer needed
actionNameif this string is non-empty, the current transaction will be given this name; if it's empty, the current transaction name will be left unchanged. See setCurrentTransactionName()
Returns
true if the command succeeds - see UndoableAction::perform
See Also
beginNewTransaction
void UndoManager::beginNewTransaction ( const String actionName = String())

Starts a new group of actions that together will be treated as a single transaction.

All actions that are passed to the perform() method between calls to this method are grouped together and undone/redone together by a single call to undo() or redo().

Parameters
actionNamea description of the transaction that is about to be performed
void UndoManager::setCurrentTransactionName ( const String newName)

Changes the name stored for the current transaction.

Each transaction is given a name when the beginNewTransaction() method is called, but this can be used to change that name without starting a new transaction.

bool UndoManager::canUndo ( ) const

Returns true if there's at least one action in the list to undo.

See Also
getUndoDescription, undo, canRedo
String UndoManager::getUndoDescription ( ) const

Returns the description of the transaction that would be next to get undone.

The description returned is the one that was passed into beginNewTransaction before the set of actions was performed.

See Also
undo
bool UndoManager::undo ( )

Tries to roll-back the last transaction.

Returns
true if the transaction can be undone, and false if it fails, or if there aren't any transactions to undo
bool UndoManager::undoCurrentTransactionOnly ( )

Tries to roll-back any actions that were added to the current transaction.

This will perform an undo() only if there are some actions in the undo list that were added after the last call to beginNewTransaction().

This is useful because it lets you call beginNewTransaction(), then perform an operation which may or may not actually perform some actions, and then call this method to get rid of any actions that might have been done without it rolling back the previous transaction if nothing was actually done.

Returns
true if any actions were undone.
void UndoManager::getActionsInCurrentTransaction ( Array< const UndoableAction * > &  actionsFound) const

Returns a list of the UndoableAction objects that have been performed during the transaction that is currently open.

Effectively, this is the list of actions that would be undone if undoCurrentTransactionOnly() were to be called now.

The first item in the list is the earliest action performed.

int UndoManager::getNumActionsInCurrentTransaction ( ) const

Returns the number of UndoableAction objects that have been performed during the transaction that is currently open.

See Also
getActionsInCurrentTransaction
Time UndoManager::getTimeOfUndoTransaction ( ) const

Returns the time to which the state would be restored if undo() was to be called.

If an undo isn't currently possible, it'll return Time().

Time UndoManager::getTimeOfRedoTransaction ( ) const

Returns the time to which the state would be restored if redo() was to be called.

If a redo isn't currently possible, it'll return Time::getCurrentTime().

bool UndoManager::canRedo ( ) const

Returns true if there's at least one action in the list to redo.

See Also
getRedoDescription, redo, canUndo
String UndoManager::getRedoDescription ( ) const

Returns the description of the transaction that would be next to get redone.

The description returned is the one that was passed into beginNewTransaction before the set of actions was performed.

See Also
redo
bool UndoManager::redo ( )

Tries to redo the last transaction that was undone.

Returns
true if the transaction can be redone, and false if it fails, or if there aren't any transactions to redo

The documentation for this class was generated from the following file: