UndoRedo

Inherits: Object

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

Description

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:

GDScriptC#

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()

private UndoRedo _undoRedo;
public override void _Ready()
{
    _undoRedo = new UndoRedo();
}
public void DoSomething()
{
    // Put your code here.
}
public void UndoSomething()
{
    // Put here the code that reverts what's done by "DoSomething()".
}
private void OnMyButtonPressed()
{
    var node = GetNode<Node2D>("MyNode2D");
    _undoRedo.CreateAction("Move the node");
    _undoRedo.AddDoMethod(new Callable(this, MethodName.DoSomething));
    _undoRedo.AddUndoMethod(new Callable(this, MethodName.UndoSomething));
    _undoRedo.AddDoProperty(node, "position", new Vector2(100, 100));
    _undoRedo.AddUndoProperty(node, "position", node.Position);
    _undoRedo.CommitAction();
}

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

If you don’t need to register a method, you can leave add_do_method and 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.

GDScriptC#

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()

_undo_redo.CreateAction("Add object");
// DO
_undo_redo.AddDoMethod(new Callable(this, MethodName.CreateObject));
_undo_redo.AddDoMethod(new Callable(this, MethodName.AddObjectToSingleton));
// UNDO
_undo_redo.AddUndoMethod(new Callable(this, MethodName.RemoveObjectFromSingleton));
_undo_redo.AddUndoMethod(new Callable(this, MethodName.DestroyThatObject));
_undo_redo.CommitAction();

Properties

Methods

Signals

version_changed() 🔗

Called when undo or redo was called.

Enumerations

enum MergeMode: 🔗

MergeMode MERGE_DISABLE = 0

Makes “do”/“undo” operations stay in separate actions.

MergeMode MERGE_ENDS = 1

Merges this action with the previous one if they have the same name. Keeps only the first action’s “undo” operations and the last action’s “do” operations. Useful for sequential changes to a single value.

MergeMode MERGE_ALL = 2

Merges this action with the previous one if they have the same name.

Property Descriptions

int max_steps = 0 🔗

• void set_max_steps(value: int)

• int get_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.

Method Descriptions

void add_do_method(callable: Callable) 🔗

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

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

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

void add_do_reference(object: 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_undo_method(callable: Callable) 🔗

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

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

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

void add_undo_reference(object: 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 clear_history(increase_version: bool = true) 🔗

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 commit_action(execute: bool = true) 🔗

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 create_action(name: String, merge_mode: MergeMode = 0, backward_undo_ops: bool = false) 🔗

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

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

String get_action_name(id: int) 🔗

Gets the action name from its index.

int get_current_action() 🔗

Gets the index of the current action.

String get_current_action_name() const 🔗

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

int get_history_count() 🔗

Returns how many elements are in the history.

int get_version() 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.

bool has_redo() const 🔗

Returns true if a “redo” action is available.

bool has_undo() const 🔗

Returns true if an “undo” action is available.

bool is_committing_action() const 🔗

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

bool redo() 🔗

Redo the last action.

void 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 MERGE_ENDS mode. Return to normal operation using end_force_keep_in_merge_ends.

bool undo() 🔗

Undo the last action.

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