Class

Undo (undo)

@ckeditor/ckeditor5-undo/src/undo

class

The undo feature.

This is a "glue" plugin which loads the undo editing feature and the undo UI feature.

Below is an explanation of the undo mechanism working together with History:

Whenever an operation is applied to the document, it is saved to History as is. The batch that owns that operation is also saved, in UndoCommand, together with the selection that was present in the document before the operation was applied. A batch is saved instead of the operation because changes are undone batch-by-batch, not operation-by-operation and a batch is seen as one undo step.

After changes happen to the document, the History and UndoCommand stack can be represented as follows:

   History                            Undo stack
==============             ==================================
[operation A1]                      [  batch A  ]
[operation B1]                      [  batch B  ]
[operation B2]                      [  batch C  ]
[operation C1]
[operation C2]
[operation B3]
[operation C3]

Where operations starting with the same letter are from same batch.

Undoing a batch means that a set of operations which will reverse the effects of that batch needs to be generated. For example, if a batch added several letters, undoing the batch should remove them. It is important to apply undoing operations in the reversed order, so if a batch has operation X, Y, Z, reversed operations Zr, Yr and Xr need to be applied. Otherwise reversed operation Xr would operate on a wrong document state, because operation X does not know that operations Y and Z happened.

After operations from an undone batch got reversed, one needs to make sure if they are ready to be applied. In the scenario above, operation C3 is the last operation and C3r bases on up-to-date document state, so it can be applied to the document.

     History                             Undo stack
=================             ==================================
[ operation A1  ]                      [  batch A  ]
[ operation B1  ]                      [  batch B  ]
[ operation B2  ]             [   processing undoing batch C   ]
[ operation C1  ]
[ operation C2  ]
[ operation B3  ]
[ operation C3  ]
[ operation C3r ]

Next is operation C2, reversed to C2r. C2r bases on C2, so it bases on the wrong document state. It needs to be transformed by operations from history that happened after it, so it "knows" about them. Let us assume that C2' = C2r * B3 * C3 * C3r, where * means "transformed by". Rest of operations from that batch are processed in the same fashion.

     History                             Undo stack                                      Redo stack
=================             ==================================             ==================================
[ operation A1  ]                      [  batch A  ]                                    [ batch Cr ]
[ operation B1  ]                      [  batch B  ]
[ operation B2  ]
[ operation C1  ]
[ operation C2  ]
[ operation B3  ]
[ operation C3  ]
[ operation C3r ]
[ operation C2' ]
[ operation C1' ]

Selective undo works on the same basis, however, instead of undoing the last batch in the undo stack, any batch can be undone. The same algorithm applies: operations from a batch (i.e. A1) are reversed and then transformed by operations stored in history.

Redo also is very similar to undo. It has its own stack that is filled with undoing (reversed batches). Operations from the batch that is re-done are reversed-back, transformed in proper order and applied to the document.

     History                             Undo stack                                      Redo stack
=================             ==================================             ==================================
[ operation A1  ]                      [  batch A  ]
[ operation B1  ]                      [  batch B  ]
[ operation B2  ]                      [ batch Crr ]
[ operation C1  ]
[ operation C2  ]
[ operation B3  ]
[ operation C3  ]
[ operation C3r ]
[ operation C2' ]
[ operation C1' ]
[ operation C1'r]
[ operation C2'r]
[ operation C3rr]

Filtering

Properties

  • readonly inherited

    editor : Editor

    The editor instance.

    Note that most editors implement the ui property. However, editors with an external UI (i.e. Bootstrap-based) or a headless editor may not have this property or throw an error when accessing it.

    Because of above, to make plugins more universal, it is recommended to split features into:

    • The "editing" part that uses the Editor class without ui property.
    • The "UI" part that uses the Editor class and accesses ui property.
  • inherited observable

    isEnabled : boolean

    Flag indicating whether a plugin is enabled or disabled. A disabled plugin will not transform text.

    Plugin can be simply disabled like that:

    // Disable the plugin so that no toolbars are visible.
    editor.plugins.get( 'TextTransformation' ).isEnabled = false;
    

    You can also use forceDisabled method.

Static properties

Methods

  • inherited

    constructor( editor )

    Parameters

    editor : Editor
  • inherited

    bind( bindProperties ) → MultiBindChain

    Binds observable properties to other objects implementing the Observable interface.

    Read more in the dedicated guide covering the topic of property bindings with some additional examples.

    Consider two objects: a button and an associated command (both Observable).

    A simple property binding could be as follows:

    button.bind( 'isEnabled' ).to( command, 'isEnabled' );
    

    or even shorter:

    button.bind( 'isEnabled' ).to( command );
    

    which works in the following way:

    • button.isEnabled instantly equals command.isEnabled,
    • whenever command.isEnabled changes, button.isEnabled will immediately reflect its value.

    Note: To release the binding, use unbind.

    You can also "rename" the property in the binding by specifying the new name in the to() chain:

    button.bind( 'isEnabled' ).to( command, 'isWorking' );
    

    It is possible to bind more than one property at a time to shorten the code:

    button.bind( 'isEnabled', 'value' ).to( command );
    

    which corresponds to:

    button.bind( 'isEnabled' ).to( command );
    button.bind( 'value' ).to( command );
    

    The binding can include more than one observable, combining multiple data sources in a custom callback:

    button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible',
    	( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
    

    Using a custom callback allows processing the value before passing it to the target property:

    button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
    

    It is also possible to bind to the same property in an array of observables. To bind a button to multiple commands (also Observables) so that each and every one of them must be enabled for the button to become enabled, use the following code:

    button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled',
    	( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
    

    Parameters

    bindProperties : Array<'off' | 'on' | 'once' | 'listenTo' | 'stopListening' | 'fire' | 'delegate' | 'stopDelegating' | 'set' | 'bind' | 'unbind' | 'decorate' | 'destroy' | 'isEnabled' | 'editor' | 'forceDisabled' | 'clearForceDisabled'>

    Observable properties that will be bound to other observable(s).

    Returns

    MultiBindChain

    The bind chain with the to() and toMany() methods.

  • inherited

    bind( bindProperty1, bindProperty2 ) → DualBindChain<K1, Undo[ K1 ], K2, Undo[ K2 ]>

    Binds observable properties to other objects implementing the Observable interface.

    Read more in the dedicated guide covering the topic of property bindings with some additional examples.

    Consider two objects: a button and an associated command (both Observable).

    A simple property binding could be as follows:

    button.bind( 'isEnabled' ).to( command, 'isEnabled' );
    

    or even shorter:

    button.bind( 'isEnabled' ).to( command );
    

    which works in the following way:

    • button.isEnabled instantly equals command.isEnabled,
    • whenever command.isEnabled changes, button.isEnabled will immediately reflect its value.

    Note: To release the binding, use unbind.

    You can also "rename" the property in the binding by specifying the new name in the to() chain:

    button.bind( 'isEnabled' ).to( command, 'isWorking' );
    

    It is possible to bind more than one property at a time to shorten the code:

    button.bind( 'isEnabled', 'value' ).to( command );
    

    which corresponds to:

    button.bind( 'isEnabled' ).to( command );
    button.bind( 'value' ).to( command );
    

    The binding can include more than one observable, combining multiple data sources in a custom callback:

    button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible',
    	( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
    

    Using a custom callback allows processing the value before passing it to the target property:

    button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
    

    It is also possible to bind to the same property in an array of observables. To bind a button to multiple commands (also Observables) so that each and every one of them must be enabled for the button to become enabled, use the following code:

    button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled',
    	( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
    

    Type parameters

    K1
    K2

    Parameters

    bindProperty1 : K1

    Observable property that will be bound to other observable(s).

    bindProperty2 : K2

    Observable property that will be bound to other observable(s).

    Returns

    DualBindChain<K1, Undo[ K1 ], K2, Undo[ K2 ]>

    The bind chain with the to() and toMany() methods.

  • inherited

    bind( bindProperty ) → SingleBindChain<K, Undo[ K ]>

    Binds observable properties to other objects implementing the Observable interface.

    Read more in the dedicated guide covering the topic of property bindings with some additional examples.

    Consider two objects: a button and an associated command (both Observable).

    A simple property binding could be as follows:

    button.bind( 'isEnabled' ).to( command, 'isEnabled' );
    

    or even shorter:

    button.bind( 'isEnabled' ).to( command );
    

    which works in the following way:

    • button.isEnabled instantly equals command.isEnabled,
    • whenever command.isEnabled changes, button.isEnabled will immediately reflect its value.

    Note: To release the binding, use unbind.

    You can also "rename" the property in the binding by specifying the new name in the to() chain:

    button.bind( 'isEnabled' ).to( command, 'isWorking' );
    

    It is possible to bind more than one property at a time to shorten the code:

    button.bind( 'isEnabled', 'value' ).to( command );
    

    which corresponds to:

    button.bind( 'isEnabled' ).to( command );
    button.bind( 'value' ).to( command );
    

    The binding can include more than one observable, combining multiple data sources in a custom callback:

    button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible',
    	( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
    

    Using a custom callback allows processing the value before passing it to the target property:

    button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
    

    It is also possible to bind to the same property in an array of observables. To bind a button to multiple commands (also Observables) so that each and every one of them must be enabled for the button to become enabled, use the following code:

    button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled',
    	( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
    

    Type parameters

    K

    Parameters

    bindProperty : K

    Observable property that will be bound to other observable(s).

    Returns

    SingleBindChain<K, Undo[ K ]>

    The bind chain with the to() and toMany() methods.

  • inherited

    clearForceDisabled( id ) → void

    Clears forced disable previously set through forceDisabled. See forceDisabled.

    Parameters

    id : string

    Unique identifier, equal to the one passed in forceDisabled call.

    Returns

    void
  • inherited

    decorate( methodName ) → void

    Turns the given methods of this object into event-based ones. This means that the new method will fire an event (named after the method) and the original action will be plugged as a listener to that event.

    Read more in the dedicated guide covering the topic of decorating methods with some additional examples.

    Decorating the method does not change its behavior (it only adds an event), but it allows to modify it later on by listening to the method's event.

    For example, to cancel the method execution the event can be stopped:

    class Foo extends ObservableMixin() {
    	constructor() {
    		super();
    		this.decorate( 'method' );
    	}
    
    	method() {
    		console.log( 'called!' );
    	}
    }
    
    const foo = new Foo();
    foo.on( 'method', ( evt ) => {
    	evt.stop();
    }, { priority: 'high' } );
    
    foo.method(); // Nothing is logged.
    

    Note: The high priority listener has been used to execute this particular callback before the one which calls the original method (which uses the "normal" priority).

    It is also possible to change the returned value:

    foo.on( 'method', ( evt ) => {
    	evt.return = 'Foo!';
    } );
    
    foo.method(); // -> 'Foo'
    

    Finally, it is possible to access and modify the arguments the method is called with:

    method( a, b ) {
    	console.log( `${ a }, ${ b }`  );
    }
    
    // ...
    
    foo.on( 'method', ( evt, args ) => {
    	args[ 0 ] = 3;
    
    	console.log( args[ 1 ] ); // -> 2
    }, { priority: 'high' } );
    
    foo.method( 1, 2 ); // -> '3, 2'
    

    Parameters

    methodName : 'off' | 'on' | 'once' | 'listenTo' | 'stopListening' | 'fire' | 'delegate' | 'stopDelegating' | 'set' | 'bind' | 'unbind' | 'decorate' | 'destroy' | 'isEnabled' | 'editor' | 'forceDisabled' | 'clearForceDisabled'

    Name of the method to decorate.

    Returns

    void
  • inherited

    delegate( events ) → EmitterMixinDelegateChain

    Delegates selected events to another Emitter. For instance:

    emitterA.delegate( 'eventX' ).to( emitterB );
    emitterA.delegate( 'eventX', 'eventY' ).to( emitterC );
    

    then eventX is delegated (fired by) emitterB and emitterC along with data:

    emitterA.fire( 'eventX', data );
    

    and eventY is delegated (fired by) emitterC along with data:

    emitterA.fire( 'eventY', data );
    

    Parameters

    events : Array<string>

    Event names that will be delegated to another emitter.

    Returns

    EmitterMixinDelegateChain
  • inherited

    destroy() → void

    Destroys the plugin.

    Note: This method is optional. A plugin instance does not need to have it defined.

    Returns

    void
  • inherited

    fire( eventOrInfo, args ) → GetEventInfo<TEvent>[ 'return' ]

    Fires an event, executing all callbacks registered for it.

    The first parameter passed to callbacks is an EventInfo object, followed by the optional args provided in the fire() method call.

    Type parameters

    TEvent : extends BaseEvent

    The type describing the event. See BaseEvent.

    Parameters

    eventOrInfo : GetNameOrEventInfo<TEvent>

    The name of the event or EventInfo object if event is delegated.

    args : TEvent[ 'args' ]

    Additional arguments to be passed to the callbacks.

    Returns

    GetEventInfo<TEvent>[ 'return' ]

    By default the method returns undefined. However, the return value can be changed by listeners through modification of the evt.return's property (the event info is the first param of every callback).

  • inherited

    forceDisabled( id ) → void

    Disables the plugin.

    Plugin may be disabled by multiple features or algorithms (at once). When disabling a plugin, unique id should be passed (e.g. feature name). The same identifier should be used when enabling back the plugin. The plugin becomes enabled only after all features enabled it back.

    Disabling and enabling a plugin:

    plugin.isEnabled; // -> true
    plugin.forceDisabled( 'MyFeature' );
    plugin.isEnabled; // -> false
    plugin.clearForceDisabled( 'MyFeature' );
    plugin.isEnabled; // -> true
    

    Plugin disabled by multiple features:

    plugin.forceDisabled( 'MyFeature' );
    plugin.forceDisabled( 'OtherFeature' );
    plugin.clearForceDisabled( 'MyFeature' );
    plugin.isEnabled; // -> false
    plugin.clearForceDisabled( 'OtherFeature' );
    plugin.isEnabled; // -> true
    

    Multiple disabling with the same identifier is redundant:

    plugin.forceDisabled( 'MyFeature' );
    plugin.forceDisabled( 'MyFeature' );
    plugin.clearForceDisabled( 'MyFeature' );
    plugin.isEnabled; // -> true
    

    Note: some plugins or algorithms may have more complex logic when it comes to enabling or disabling certain plugins, so the plugin might be still disabled after clearForceDisabled was used.

    Parameters

    id : string

    Unique identifier for disabling. Use the same id when enabling back the plugin.

    Returns

    void
  • inherited

    listenTo( emitter, event, callback, [ options ] ) → void

    Registers a callback function to be executed when an event is fired in a specific (emitter) object.

    Events can be grouped in namespaces using :. When namespaced event is fired, it additionally fires all callbacks for that namespace.

    // myEmitter.on( ... ) is a shorthand for myEmitter.listenTo( myEmitter, ... ).
    myEmitter.on( 'myGroup', genericCallback );
    myEmitter.on( 'myGroup:myEvent', specificCallback );
    
    // genericCallback is fired.
    myEmitter.fire( 'myGroup' );
    // both genericCallback and specificCallback are fired.
    myEmitter.fire( 'myGroup:myEvent' );
    // genericCallback is fired even though there are no callbacks for "foo".
    myEmitter.fire( 'myGroup:foo' );
    

    An event callback can stop the event and set the return value of the fire method.

    Type parameters

    TEvent : extends BaseEvent

    The type describing the event. See BaseEvent.

    Parameters

    emitter : Emitter

    The object that fires the event.

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : GetCallbackOptions<TEvent>

    Additional options.

    Returns

    void
  • inherited

    off( event, callback ) → void

    Stops executing the callback on the given event. Shorthand for this.stopListening( this, event, callback ).

    Parameters

    event : string

    The name of the event.

    callback : Function

    The function to stop being called.

    Returns

    void
  • inherited

    on( event, callback, [ options ] ) → void

    Registers a callback function to be executed when an event is fired.

    Shorthand for this.listenTo( this, event, callback, options ) (it makes the emitter listen on itself).

    Type parameters

    TEvent : extends BaseEvent

    The type descibing the event. See BaseEvent.

    Parameters

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : GetCallbackOptions<TEvent>

    Additional options.

    Returns

    void
  • inherited

    once( event, callback, [ options ] ) → void

    Registers a callback function to be executed on the next time the event is fired only. This is similar to calling on followed by off in the callback.

    Type parameters

    TEvent : extends BaseEvent

    The type descibing the event. See BaseEvent.

    Parameters

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : GetCallbackOptions<TEvent>

    Additional options.

    Returns

    void
  • inherited

    set( values ) → void

    Creates and sets the value of an observable properties of this object. Such a property becomes a part of the state and is observable.

    It accepts a single object literal containing key/value pairs with properties to be set.

    This method throws the observable-set-cannot-override error if the observable instance already has a property with the given property name. This prevents from mistakenly overriding existing properties and methods, but means that foo.set( 'bar', 1 ) may be slightly slower than foo.bar = 1.

    In TypeScript, those properties should be declared in class using declare keyword. In example:

    public declare myProp1: number;
    public declare myProp2: string;
    
    constructor() {
    	this.set( {
    		'myProp1: 2,
    		'myProp2: 'foo'
    	} );
    }
    

    Parameters

    values : object

    An object with name=>value pairs.

    Returns

    void
  • inherited

    set( name, value ) → void

    Creates and sets the value of an observable property of this object. Such a property becomes a part of the state and is observable.

    This method throws the observable-set-cannot-override error if the observable instance already has a property with the given property name. This prevents from mistakenly overriding existing properties and methods, but means that foo.set( 'bar', 1 ) may be slightly slower than foo.bar = 1.

    In TypeScript, those properties should be declared in class using declare keyword. In example:

    public declare myProp: number;
    
    constructor() {
    	this.set( 'myProp', 2 );
    }
    

    Type parameters

    K

    Parameters

    name : K

    The property's name.

    value : Undo[ K ]

    The property's value.

    Returns

    void
  • inherited

    stopDelegating( [ event ], [ emitter ] ) → void

    Stops delegating events. It can be used at different levels:

    • To stop delegating all events.
    • To stop delegating a specific event to all emitters.
    • To stop delegating a specific event to a specific emitter.

    Parameters

    [ event ] : string

    The name of the event to stop delegating. If omitted, stops it all delegations.

    [ emitter ] : Emitter

    (requires event) The object to stop delegating a particular event to. If omitted, stops delegation of event to all emitters.

    Returns

    void
  • inherited

    stopListening( [ emitter ], [ event ], [ callback ] ) → void

    Stops listening for events. It can be used at different levels:

    • To stop listening to a specific callback.
    • To stop listening to a specific event.
    • To stop listening to all events fired by a specific object.
    • To stop listening to all events fired by all objects.

    Parameters

    [ emitter ] : Emitter

    The object to stop listening to. If omitted, stops it for all objects.

    [ event ] : string

    (Requires the emitter) The name of the event to stop listening to. If omitted, stops it for all events from emitter.

    [ callback ] : Function

    (Requires the event) The function to be removed from the call list for the given event.

    Returns

    void
  • inherited

    unbind( unbindProperties ) → void

    Removes the binding created with bind.

    // Removes the binding for the 'a' property.
    A.unbind( 'a' );
    
    // Removes bindings for all properties.
    A.unbind();
    

    Parameters

    unbindProperties : Array<'off' | 'on' | 'once' | 'listenTo' | 'stopListening' | 'fire' | 'delegate' | 'stopDelegating' | 'set' | 'bind' | 'unbind' | 'decorate' | 'destroy' | 'isEnabled' | 'editor' | 'forceDisabled' | 'clearForceDisabled'>

    Observable properties to be unbound. All the bindings will be released if no properties are provided.

    Returns

    void

Events

  • inherited

    change:isEnabled( eventInfo, name, value, oldValue )

    Fired when the isEnabled property changed value.

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    name : string

    Name of the changed property (isEnabled).

    value : boolean

    New value of the isEnabled property with given key or null, if operation should remove property.

    oldValue : boolean

    Old value of the isEnabled property with given key or null, if property was not set before.

  • inherited

    change:{property}( eventInfo, name, value, oldValue )

    Fired when a property changed value.

    observable.set( 'prop', 1 );
    
    observable.on<ObservableChangeEvent<number>>( 'change:prop', ( evt, propertyName, newValue, oldValue ) => {
    	console.log( `${ propertyName } has changed from ${ oldValue } to ${ newValue }` );
    } );
    
    observable.prop = 2; // -> 'prop has changed from 1 to 2'
    

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    name : string

    The property name.

    value : TValue

    The new property value.

    oldValue : TValue

    The previous property value.

  • inherited

    set:isEnabled( eventInfo, name, value, oldValue )

    Fired when the isEnabled property is going to be set but is not set yet (before the change event is fired).

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    name : string

    Name of the changed property (isEnabled).

    value : boolean

    New value of the isEnabled property with given key or null, if operation should remove property.

    oldValue : boolean

    Old value of the isEnabled property with given key or null, if property was not set before.

  • inherited

    set:{property}( eventInfo, name, value, oldValue )

    Fired when a property value is going to be set but is not set yet (before the change event is fired).

    You can control the final value of the property by using the event's return property.

    observable.set( 'prop', 1 );
    
    observable.on<ObservableSetEvent<number>>( 'set:prop', ( evt, propertyName, newValue, oldValue ) => {
    	console.log( `Value is going to be changed from ${ oldValue } to ${ newValue }` );
    	console.log( `Current property value is ${ observable[ propertyName ] }` );
    
    	// Let's override the value.
    	evt.return = 3;
    } );
    
    observable.on<ObservableChangeEvent<number>>( 'change:prop', ( evt, propertyName, newValue, oldValue ) => {
    	console.log( `Value has changed from ${ oldValue } to ${ newValue }` );
    } );
    
    observable.prop = 2; // -> 'Value is going to be changed from 1 to 2'
                         // -> 'Current property value is 1'
                         // -> 'Value has changed from 1 to 3'
    

    Note: The event is fired even when the new value is the same as the old value.

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    name : string

    The property name.

    value : TValue

    The new property value.

    oldValue : TValue

    The previous property value.