SelectionObserver (engine/view/observer)



Selection observer class observes selection changes in the document. If a selection changes on the document this observer checks if there are any mutations and if the DOM selection is different from the view selection. The selection observer fires event-selectionChange event only if a selection change was the only change in the document and the DOM selection is different then the view selection.

This observer also manages the isSelecting property of the view document.

Note that this observer is attached by the View and is available by default.



  • document : Document

    readonly inherited

    A reference to the Document object.

  • domConverter : DomConverter


    Reference to the domConverter.

  • isEnabled : Boolean

    readonly inherited

    The state of the observer. If it is disabled, no events will be fired.

  • mutationObserver : MutationObserver


    Instance of the mutation observer. Selection observer calls flush to ensure that the mutations will be handled before the event-selectionChange event is fired.

  • selection : DocumentSelection


    Reference to the view DocumentSelection object used to compare new selection with it.

  • view : View

    readonly inherited

    An instance of the view controller.

  • _clearInfiniteLoopInterval : Number


    When called, starts clearing the _loopbackCounter counter in time intervals. When the number of selection changes exceeds a certain limit within the interval of time, the observer will not fire selectionChange but warn about possible infinite selection loop.

  • _documents : WeakSet.<Document>


    A set of documents which have added selectionchange listener to avoid adding a listener twice to the same document.

  • _loopbackCounter : Number


    Private property to check if the code does not enter infinite loop.


  • checkShouldIgnoreEventFromTarget( domTarget ) → Boolean


    Checks whether a given DOM event should be ignored (should not be turned into a synthetic view document event).

    Currently, an event will be ignored only if its target or any of its ancestors has the data-cke-ignore-events attribute. This attribute can be used inside the structures generated by DowncastWriter#createUIElement() to ignore events fired within a UI that should be excluded from CKEditor 5's realms.


    domTarget : Node

    The DOM event target to check (usually an element, sometimes a text node and potentially sometimes a document, too).



    Whether this event should be ignored by the observer.

  • destroy()


    Disables and destroys the observer, among others removes event listeners created by the observer.

  • disable()


    Disables the observer. This method is called before rendering to prevent firing events during rendering.


  • enable()


    Enables the observer. This method is called when the observer is registered to the View and after rendering (all observers are disabled before rendering).

    A typical use case for disabling observers is that mutation observers need to be disabled for the rendering. However, a child class may not need to be disabled, so it can implement an empty method.


  • observe( domElement, name )


    Starts observing the given root element.


    domElement : HTMLElement
    name : String

    The name of the root element.

  • _clearInfiniteLoop()


    Clears SelectionObserver internal properties connected with preventing infinite loop.

  • _documentIsSelectingInactivityTimeoutDebounced()


    Unlocks the isSelecting state of the view document in case the selection observer did not record this fact correctly (for whatever reason). It is a safeguard (paranoid check), that returns document to the normal state after a certain period of time (debounced, postponed by each selectionchange event).

  • _fireSelectionChangeDoneDebounced( data )


    Fires debounced event selectionChangeDone. It uses lodash#debounce method to delay function call.


    data : Object

    Selection change data.

  • _handleSelectionChange( domEvent, domDocument )


    Selection change listener. Flush mutations, check if a selection changes and fires event-selectionChange event on every change and event-selectionChangeDone when a selection stop changing.


    domEvent : Event

    DOM event.

    domDocument : Document

    DOM document.