juce::UndoManager Class Reference

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

#include <juce_UndoManager.h>

Inheritance diagram for juce::UndoManager:

Collaboration diagram for juce::UndoManager:

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

Private Member Functions
void	callListeners ()
void	dropOldTransactionsIfTooLarge ()
ActionSet *	getCurrentSet () const
ActionSet *	getNextSet () const
void	moveFutureTransactionsToStash ()
void	restoreStashedFutureTransactions ()

Private Attributes
std::atomic< bool >	anyListeners { false }
ChangeBroadcasterCallback	broadcastCallback
ListenerList< ChangeListener >	changeListeners
bool	isInsideUndoRedoCall = false
int	maxNumUnitsToKeep = 0
int	minimumTransactionsToKeep = 0
bool	newTransaction = true
String	newTransactionName
int	nextIndex = 0
OwnedArray< ActionSet >	stashedFutureTransactions
int	totalUnitsStored = 0
OwnedArray< ActionSet >	transactions

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

@tags{DataStructures}

Constructor & Destructor Documentation

UndoManager()

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

Creates an UndoManager.

Parameters

maxNumberOfUnitsToKeep	each 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.
minimumTransactionsToKeep	this specifies the minimum number of transactions that will be kept, even if this involves exceeding the amount of space specified in maxNumberOfUnitsToKeep

~UndoManager()

juce::UndoManager::~UndoManager ( )

override

Destructor.

Member Function Documentation

addChangeListener()

void juce::ChangeBroadcaster::addChangeListener ( ChangeListener *  listener )

inherited

Registers a listener to receive change callbacks from this broadcaster.

Trying to add a listener that's already on the list will have no effect.

beginNewTransaction() [1/2]

void juce::UndoManager::beginNewTransaction

(

)

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().

beginNewTransaction() [2/2]

void juce::UndoManager::beginNewTransaction

(

const String &

actionName

)

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

actionName

a description of the transaction that is about to be performed

callListeners()

void juce::ChangeBroadcaster::callListeners ( )

privateinherited

canRedo()

bool juce::UndoManager::canRedo

(

)

const

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

See also

getRedoDescription, redo, canUndo

canUndo()

bool juce::UndoManager::canUndo

(

)

const

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

See also

getUndoDescription, undo, canRedo

clearUndoHistory()

void juce::UndoManager::clearUndoHistory

(

)

Deletes all stored actions in the list.

dispatchPendingMessages()

void juce::ChangeBroadcaster::dispatchPendingMessages ( )

inherited

If a change message has been sent but not yet dispatched, this will call sendSynchronousChangeMessage() to make the callback immediately.

For thread-safety reasons, you must only call this method on the main message thread.

dropOldTransactionsIfTooLarge()

void juce::UndoManager::dropOldTransactionsIfTooLarge ( )

private

getActionsInCurrentTransaction()

void juce::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.

getCurrentSet()

ActionSet* juce::UndoManager::getCurrentSet ( ) const

private

getCurrentTransactionName()

String juce::UndoManager::getCurrentTransactionName

(

)

const

Returns the name of the current transaction.

See also

setCurrentTransactionName

getNextSet()

ActionSet* juce::UndoManager::getNextSet ( ) const

private

getNumActionsInCurrentTransaction()

int juce::UndoManager::getNumActionsInCurrentTransaction

(

)

const

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

See also

getActionsInCurrentTransaction

getNumberOfUnitsTakenUpByStoredCommands()

int juce::UndoManager::getNumberOfUnitsTakenUpByStoredCommands

(

)

const

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

See also

setMaxNumberOfStoredUnits

getRedoDescription()

String juce::UndoManager::getRedoDescription

(

)

const

Returns the name of the transaction that will be redone when redo() is called.

See also

redo, canRedo, getRedoDescriptions

getRedoDescriptions()

StringArray juce::UndoManager::getRedoDescriptions

(

)

const

Returns the names of the sequence of transactions that will be performed if redo() is repeatedly called.

Note that for transactions where no name was provided, the corresponding string will be empty.

See also

redo, canRedo, getRedoDescription

getTimeOfRedoTransaction()

Time juce::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().

See also

redo, canRedo

getTimeOfUndoTransaction()

Time juce::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().

getUndoDescription()

String juce::UndoManager::getUndoDescription

(

)

const

Returns the name of the transaction that will be rolled-back when undo() is called.

See also

undo, canUndo, getUndoDescriptions

getUndoDescriptions()

StringArray juce::UndoManager::getUndoDescriptions

(

)

const

Returns the names of the sequence of transactions that will be performed if undo() is repeatedly called.

Note that for transactions where no name was provided, the corresponding string will be empty.

See also

undo, canUndo, getUndoDescription

isPerformingUndoRedo()

bool juce::UndoManager::isPerformingUndoRedo

(

)

const

Returns true if the caller code is in the middle of an undo or redo action.

moveFutureTransactionsToStash()

void juce::UndoManager::moveFutureTransactionsToStash ( )

private

perform() [1/2]

bool juce::UndoManager::perform

(

UndoableAction *

action

)

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

Parameters

action

the action to perform - this object will be deleted by the UndoManager when no longer needed

Returns

true if the command succeeds - see UndoableAction::perform

See also

beginNewTransaction

perform() [2/2]

bool juce::UndoManager::perform	(	UndoableAction *	action,
		const String &	actionName
	)

Performs an action and also gives it a name.

Parameters

action	the action to perform - this object will be deleted by the UndoManager when no longer needed
actionName	if 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

redo()

bool juce::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

removeAllChangeListeners()

void juce::ChangeBroadcaster::removeAllChangeListeners ( )

inherited

Removes all listeners from the list.

removeChangeListener()

void juce::ChangeBroadcaster::removeChangeListener ( ChangeListener *  listener )

inherited

Unregisters a listener from the list.

If the listener isn't on the list, this won't have any effect.

restoreStashedFutureTransactions()

void juce::UndoManager::restoreStashedFutureTransactions ( )

private

sendChangeMessage()

void juce::ChangeBroadcaster::sendChangeMessage ( )

inherited

Causes an asynchronous change message to be sent to all the registered listeners.

The message will be delivered asynchronously by the main message thread, so this method will return immediately. To call the listeners synchronously use sendSynchronousChangeMessage().

Referenced by juce::SelectedItemSet< SelectableItemType >::changed().

sendSynchronousChangeMessage()

void juce::ChangeBroadcaster::sendSynchronousChangeMessage ( )

inherited

Sends a synchronous change message to all the registered listeners.

This will immediately call all the listeners that are registered. For thread-safety reasons, you must only call this method on the main message thread.

See also

dispatchPendingMessages

Referenced by juce::SelectedItemSet< SelectableItemType >::changed().

setCurrentTransactionName()

void juce::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.

setMaxNumberOfStoredUnits()

void juce::UndoManager::setMaxNumberOfStoredUnits	(	int	maxNumberOfUnitsToKeep,
		int	minimumTransactionsToKeep
	)

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

Parameters

maxNumberOfUnitsToKeep	each 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.
minimumTransactionsToKeep	this 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

undo()

bool juce::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

See also

undoCurrentTransactionOnly

undoCurrentTransactionOnly()

bool juce::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.

Member Data Documentation

anyListeners

std::atomic<bool> juce::ChangeBroadcaster::anyListeners { false }

privateinherited

broadcastCallback

ChangeBroadcasterCallback juce::ChangeBroadcaster::broadcastCallback

privateinherited

changeListeners

ListenerList<ChangeListener> juce::ChangeBroadcaster::changeListeners

privateinherited

isInsideUndoRedoCall

bool juce::UndoManager::isInsideUndoRedoCall = false

private

maxNumUnitsToKeep

int juce::UndoManager::maxNumUnitsToKeep = 0

private

minimumTransactionsToKeep

int juce::UndoManager::minimumTransactionsToKeep = 0

private

newTransaction

bool juce::UndoManager::newTransaction = true

private

newTransactionName

String juce::UndoManager::newTransactionName

private

nextIndex

int juce::UndoManager::nextIndex = 0

private

stashedFutureTransactions

OwnedArray<ActionSet> juce::UndoManager::stashedFutureTransactions

private

totalUnitsStored

int juce::UndoManager::totalUnitsStored = 0

private

transactions

OwnedArray<ActionSet> juce::UndoManager::transactions

private

---

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

• juce_UndoManager.h