Class UndoRedo

Provides a high-level interface for implementing undo and redo operations.

Inheritance

Object

UndoRedo

Remarks

UndoRedo works by registering methods and property changes inside "actions". You can create an action, then provide ways to do and undo this action using function calls and property changes, then commit the action.

When an action is committed, all of the do_* methods will run. If the undo method is used, the undo_* methods will run. If the redo method is used, once again, all of the do_* methods will run.

Here's an example on how to add an action:

• gdscript
• C#

var undo_redo = UndoRedo.new()

func do_something():
    pass # Put your code here.

func undo_something():
    pass # Put here the code that reverts what's done by "do_something()".

func _on_my_button_pressed():
    var node = get_node("MyNode2D")
    undo_redo.create_action("Move the node")
    undo_redo.add_do_method(do_something)
    undo_redo.add_undo_method(undo_something)
    undo_redo.add_do_property(node, "position", Vector2(100,100))
    undo_redo.add_undo_property(node, "position", node.position)
    undo_redo.commit_action()

Before calling any of the add_(un)do_* methods, you need to first call UndoRedo.create_action. Afterwards you need to call UndoRedo.commit_action.

If you don't need to register a method, you can leave UndoRedo.add_do_method and UndoRedo.add_undo_method out; the same goes for properties. You can also register more than one method/property.

If you are making an EditorPlugin and want to integrate into the editor's undo history, use EditorUndoRedoManager instead.

If you are registering multiple properties/method which depend on one another, be aware that by default undo operation are called in the same order they have been added. Therefore instead of grouping do operation with their undo operations it is better to group do on one side and undo on the other as shown below.

• gdscript
• C#

undo_redo.create_action("Add object")

# DO
undo_redo.add_do_method(_create_object)
undo_redo.add_do_method(_add_object_to_singleton)

# UNDO
undo_redo.add_undo_method(_remove_object_from_singleton)
undo_redo.add_undo_method(_destroy_that_object)

undo_redo.commit_action()

Properties

max_steps

The maximum number of steps that can be stored in the undo/redo history. If the number of stored steps exceeds this limit, older steps are removed from history and can no longer be reached by calling undo. A value of 0 or lower means no limit.

var max_steps : int = 0

Property Value

int

Remarks

• void set_max_steps(int value)
• int get_max_steps

Methods

add_do_method(Callable)

Register a Callable that will be called when the action is committed.

void add_do_method(Callable callable)

Parameters

callable Callable

add_do_property(Object, StringName, Variant)

Register a property that would change its value to value when the action is committed.

void add_do_property(Object object, StringName property, Variant value)

Parameters

object Object

property StringName

value Variant

add_do_reference(Object)

Register a reference to an object that will be erased if the "do" history is deleted. This is useful for objects added by the "do" action and removed by the "undo" action.

When the "do" history is deleted, if the object is a RefCounted, it will be unreferenced. Otherwise, it will be freed. Do not use for resources.

var node = Node2D.new()
undo_redo.create_action("Add node")
undo_redo.add_do_method(add_child.bind(node))
undo_redo.add_do_reference(node)
undo_redo.add_undo_method(remove_child.bind(node))
undo_redo.commit_action()

void add_do_reference(Object object)

Parameters

object Object

add_undo_method(Callable)

Register a Callable that will be called when the action is undone.

void add_undo_method(Callable callable)

Parameters

callable Callable

add_undo_property(Object, StringName, Variant)

Register a property that would change its value to value when the action is undone.

void add_undo_property(Object object, StringName property, Variant value)

Parameters

object Object

property StringName

value Variant

add_undo_reference(Object)

Register a reference to an object that will be erased if the "undo" history is deleted. This is useful for objects added by the "undo" action and removed by the "do" action.

When the "undo" history is deleted, if the object is a RefCounted, it will be unreferenced. Otherwise, it will be freed. Do not use for resources.

var node = $Node2D
undo_redo.create_action("Remove node")
undo_redo.add_do_method(remove_child.bind(node))
undo_redo.add_undo_method(add_child.bind(node))
undo_redo.add_undo_reference(node)
undo_redo.commit_action()

void add_undo_reference(Object object)

Parameters

object Object

clear_history(bool)

Clear the undo/redo history and associated references.

Passing false to increase_version will prevent the version number from increasing when the history is cleared.

void clear_history(bool increase_version)

Parameters

increase_version bool

commit_action(bool)

Commit the action. If execute is true (which it is by default), all "do" methods/properties are called/set when this function is called.

void commit_action(bool execute)

Parameters

execute bool

create_action(String, int, bool)

Create a new action. After this is called, do all your calls to UndoRedo.add_do_method, UndoRedo.add_undo_method, UndoRedo.add_do_property, and UndoRedo.add_undo_property, then commit the action with UndoRedo.commit_action.

The way actions are merged is dictated by merge_mode. See MergeMode for details.

The way undo operation are ordered in actions is dictated by backward_undo_ops. When backward_undo_ops is false undo option are ordered in the same order they were added. Which means the first operation to be added will be the first to be undone.

void create_action(String name, int merge_mode, bool backward_undo_ops)

Parameters

name String

merge_mode int

backward_undo_ops bool

end_force_keep_in_merge_ends

Stops marking operations as to be processed even if the action gets merged with another in the UndoRedo.MERGE_ENDS mode. See start_force_keep_in_merge_ends.

void end_force_keep_in_merge_ends

get_action_name(int)

Gets the action name from its index.

String get_action_name(int id)

Parameters

id int

get_current_action

Gets the index of the current action.

int get_current_action

get_current_action_name

Qualifiers: const

Gets the name of the current action, equivalent to get_action_name(get_current_action()).

String get_current_action_name

get_history_count

Returns how many elements are in the history.

int get_history_count

get_version

Qualifiers: const

Gets the version. Every time a new action is committed, the UndoRedo's version number is increased automatically.

This is useful mostly to check if something changed from a saved version.

int get_version

has_redo

Qualifiers: const

Returns true if a "redo" action is available.

bool has_redo

has_undo

Qualifiers: const

Returns true if an "undo" action is available.

bool has_undo

is_committing_action

Qualifiers: const

Returns true if the UndoRedo is currently committing the action, i.e. running its "do" method or property change (see UndoRedo.commit_action).

bool is_committing_action

redo

Redo the last action.

bool redo

start_force_keep_in_merge_ends

Marks the next "do" and "undo" operations to be processed even if the action gets merged with another in the UndoRedo.MERGE_ENDS mode. Return to normal operation using end_force_keep_in_merge_ends.

void start_force_keep_in_merge_ends

undo

Undo the last action.

bool undo

Events

version_changed

Called when undo or redo was called.

signal version_changed