View (engine/view)
@ckeditor/ckeditor5-engine/src/view/view
Editor's view controller class. Its main responsibility is DOM - View management for editing purposes, to provide abstraction over the DOM structure and events and hide all browsers quirks.
View controller renders view document to DOM whenever view structure changes. To determine when view can be rendered,
all changes need to be done using the change
method, using
DowncastWriter
:
view.change( writer => {
writer.insert( position, writer.createText( 'foo' ) );
} );
View controller also register observers which observes changes on DOM and fire events on the Document. Note that the following observers are added by the class constructor and are always available:
SelectionObserver
,FocusObserver
,KeyObserver
,FakeSelectionObserver
.CompositionObserver
.InputObserver
.ArrowKeysObserver
.TabObserver
.
This class also binds the DOM and the view elements.
If you do not need full a DOM - view management, and only want to transform a tree of view elements to a tree of DOM elements you do not need this controller. You can use the DomConverter instead.
Filtering
Properties
-
Instance of the
Document
associated with this view controller. -
domConverter : DomConverter
module:engine/view/view~View#domConverter
readonly
Instance of the domConverter used by renderer and observers.
-
domRoots : Map.<String, HTMLElement>
module:engine/view/view~View#domRoots
readonly
Roots of the DOM tree. Map on the
HTMLElement
s with roots names as keys. -
hasDomSelection : Boolean
module:engine/view/view~View#hasDomSelection
readonly
Informs whether the DOM selection is inside any of the DOM roots managed by the view.
-
isRenderingInProgress : Boolean
module:engine/view/view~View#isRenderingInProgress
readonly
Used to prevent calling
forceRender
andchange
during rendering view to the DOM. -
Instance of the renderer.
-
_hasChangedSinceTheLastRendering : Boolean
module:engine/view/view~View#_hasChangedSinceTheLastRendering
private
Internal flag that disables rendering when there are no changes since the last rendering. It stores information about changed selection and changed elements from attached document roots.
-
_initialDomRootAttributes : WeakMap.<HTMLElement, Object>
module:engine/view/view~View#_initialDomRootAttributes
private
A DOM root attributes cache. It saves the initial values of DOM root attributes before the DOM element is attached to the view so later on, when the view is destroyed (
detachDomRoot
), they can be easily restored. This way, the DOM element can go back to the (clean) state as if the editing view never used it. -
_observers : Map.<Function, Observer>
module:engine/view/view~View#_observers
private
Map of registered observers.
-
_ongoingChange : Boolean
module:engine/view/view~View#_ongoingChange
private
Is set to
true
when view changes are currently in progress. -
_postFixersInProgress : Boolean
module:engine/view/view~View#_postFixersInProgress
private
Used to prevent calling
forceRender
andchange
during rendering view to the DOM. -
_renderingDisabled : Boolean
module:engine/view/view~View#_renderingDisabled
private
Internal flag to temporary disable rendering. See the usage in the
_disableRendering
. -
_writer : DowncastWriter
module:engine/view/view~View#_writer
private
DowncastWriter instance used in change method callbacks.
Methods
-
constructor( stylesProcessor )
module:engine/view/view~View#constructor
Parameters
stylesProcessor : StylesProcessor
The styles processor instance.
-
addObserver( Observer ) → Observer
module:engine/view/view~View#addObserver
Creates observer of the given type if not yet created, enables it and attaches to all existing and future DOM roots.
Note: Observers are recognized by their constructor (classes). A single observer will be instantiated and used only when registered for the first time. This means that features and other components can register a single observer multiple times without caring whether it has been already added or not.
Parameters
Observer : function
The constructor of an observer to add. Should create an instance inheriting from
Observer
.
Returns
Observer
Added observer instance.
-
attachDomRoot( domRoot, [ name ] )
module:engine/view/view~View#attachDomRoot
Attaches a DOM root element to the view element and enable all observers on that element. Also mark element to be synchronized with the view what means that all child nodes will be removed and replaced with content of the view root.
This method also will change view element name as the same as tag name of given dom root. Name is always transformed to lower case.
Note: Use
detachDomRoot()
to revert this action.Parameters
domRoot : Element
DOM root element.
[ name ] : String
Name of the root.
Defaults to
'main'
-
bind( bindProperties ) → Object
module:engine/view/view~View#bind
mixed
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 associatedcommand
(bothObservable
).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 equalscommand.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 (alsoObservables
) 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 : String
Observable properties that will be bound to other observable(s).
Returns
Object
The bind chain with the
to()
andtoMany()
methods.
-
change( callback ) → *
module:engine/view/view~View#change
The
change()
method is the primary way of changing the view. You should use it to modify any node in the view tree. It makes sure that after all changes are made the view is rendered to the DOM (assuming that the view will be changed inside the callback). It prevents situations when the DOM is updated when the view state is not yet correct. It allows to nest calls one inside another and still performs a single rendering after all those changes are made. It also returns the return value of its callback.const text = view.change( writer => { const newText = writer.createText( 'foo' ); writer.insert( position1, newText ); view.change( writer => { writer.insert( position2, writer.createText( 'bar' ) ); } ); writer.remove( range ); return newText; } );
When the outermost change block is done and rendering to the DOM is over the
View#render
event is fired.This method throws a
applying-view-changes-on-rendering
error when the change block is used after rendering to the DOM has started.Parameters
callback : function
Callback function which may modify the view.
Returns
*
Value returned by the callback.
-
createPositionAfter( item ) → Position
module:engine/view/view~View#createPositionAfter
Creates a new position after given view item.
-
createPositionAt( itemOrPosition, [ offset ] )
module:engine/view/view~View#createPositionAt
Creates position at the given location. The location can be specified as:
-
createPositionBefore( item ) → Position
module:engine/view/view~View#createPositionBefore
Creates a new position before given view item.
-
createRange( start, [ end ] ) → Range
module:engine/view/view~View#createRange
Creates a range spanning from
start
position toend
position. -
createRangeIn( element ) → Range
module:engine/view/view~View#createRangeIn
Creates a range inside an element which starts before the first child of that element and ends after the last child of that element.
-
createRangeOn( item ) → Range
module:engine/view/view~View#createRangeOn
Creates a range that starts before given view item and ends after it.
-
createSelection( [ selectable ], [ placeOrOffset ], [ options ] = { [options.backward], [options.fake], [options.label] } ) → Selection
module:engine/view/view~View#createSelection
Creates new
Selection
instance.// Creates empty selection without ranges. const selection = view.createSelection(); // Creates selection at the given range. const range = view.createRange( start, end ); const selection = view.createSelection( range ); // Creates selection at the given ranges const ranges = [ view.createRange( start1, end2 ), view.createRange( star2, end2 ) ]; const selection = view.createSelection( ranges ); // Creates selection from the other selection. const otherSelection = view.createSelection(); const selection = view.createSelection( otherSelection ); // Creates selection from the document selection. const selection = view.createSelection( editor.editing.view.document.selection ); // Creates selection at the given position. const position = view.createPositionFromPath( root, path ); const selection = view.createSelection( position ); // Creates collapsed selection at the position of given item and offset. const paragraph = view.createContainerElement( 'paragraph' ); const selection = view.createSelection( paragraph, offset ); // Creates a range inside an element which starts before the // first child of that element and ends after the last child of that element. const selection = view.createSelection( paragraph, 'in' ); // Creates a range on an item which starts before the item and ends // just after the item. const selection = view.createSelection( paragraph, 'on' );
Selection
's factory method allow passing additional options (backward
,fake
andlabel
) as the last argument.// Creates backward selection. const selection = view.createSelection( range, { backward: true } );
Fake selection does not render as browser native selection over selected elements and is hidden to the user. This way, no native selection UI artifacts are displayed to the user and selection over elements can be represented in other way, for example by applying proper CSS class.
Additionally fake's selection label can be provided. It will be used to describe fake selection in DOM (and be properly handled by screen readers).
// Creates fake selection with label. const selection = view.createSelection( range, { fake: true, label: 'foo' } );
Parameters
[ selectable ] : Selectable
[ placeOrOffset ] : Number | 'before' | 'end' | 'after' | 'on' | 'in'
Offset or place when selectable is an
Item
.[ options ] : Object
-
Properties
[ options.backward ] : Boolean
Sets this selection instance to be backward.
[ options.fake ] : Boolean
Sets this selection instance to be marked as
fake
.[ options.label ] : String
Label for the fake selection.
Returns
-
decorate( methodName )
module:engine/view/view~View#decorate
mixed
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 { constructor() { 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 : String
Name of the method to decorate.
-
delegate( events ) → EmitterMixinDelegateChain
module:engine/view/view~View#delegate
mixed
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
andemitterC
along withdata
:emitterA.fire( 'eventX', data );
and
eventY
is delegated (fired by)emitterC
along withdata
:emitterA.fire( 'eventY', data );
Parameters
events : String
Event names that will be delegated to another emitter.
Returns
-
destroy()
module:engine/view/view~View#destroy
Destroys this instance. Makes sure that all observers are destroyed and listeners removed.
-
detachDomRoot( name )
module:engine/view/view~View#detachDomRoot
Detaches a DOM root element from the view element and restores its attributes to the state before
attachDomRoot()
.Parameters
name : String
Name of the root to detach.
-
disableObservers()
module:engine/view/view~View#disableObservers
Disables all added observers.
-
enableObservers()
module:engine/view/view~View#enableObservers
Enables all added observers.
-
fire( eventOrInfo, [ args ] ) → *
module:engine/view/view~View#fire
mixed
Fires an event, executing all callbacks registered for it.
The first parameter passed to callbacks is an
EventInfo
object, followed by the optionalargs
provided in thefire()
method call.Parameters
eventOrInfo : String | EventInfo
The name of the event or
EventInfo
object if event is delegated.[ args ] : *
Additional arguments to be passed to the callbacks.
Returns
*
By default the method returns
undefined
. However, the return value can be changed by listeners through modification of theevt.return
's property (the event info is the first param of every callback).
-
focus()
module:engine/view/view~View#focus
It will focus DOM element representing EditableElement that is currently having selection inside.
-
forceRender()
module:engine/view/view~View#forceRender
Forces rendering view document to DOM. If any view changes are currently in progress, rendering will start after all change blocks are processed.
Note that this method is dedicated for special cases. All view changes should be wrapped in the
change
block and the view will automatically check whether it needs to render DOM or not.Throws CKEditorError
applying-view-changes-on-rendering
when trying to re-render when rendering to DOM has already started. -
getDomRoot( [ name ] ) → Element
module:engine/view/view~View#getDomRoot
Gets DOM root element.
Parameters
[ name ] : String
Name of the root.
Defaults to
'main'
Returns
Element
DOM root element instance.
-
getObserver( Observer ) → Observer | undefined
module:engine/view/view~View#getObserver
Returns observer of the given type or
undefined
if such observer has not been added yet.Parameters
Observer : function
The constructor of an observer to get.
Returns
Observer | undefined
Observer instance or undefined.
-
listenTo( emitter, event, callback, [ options ] = { [options.priority] } )
module:engine/view/view~View#listenTo
mixed
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.Parameters
emitter : Emitter
The object that fires the event.
event : String
The name of the event.
callback : function
The function to be called on event.
[ options ] : Object
Additional options.
Properties[ options.priority ] : PriorityString | Number
The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.
Defaults to
'normal'
Defaults to
{}
-
off( event, callback )
module:engine/view/view~View#off
mixed
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.
-
on( event, callback, [ options ] = { [options.priority] } )
module:engine/view/view~View#on
mixed
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).Parameters
event : String
The name of the event.
callback : function
The function to be called on event.
[ options ] : Object
Additional options.
Properties[ options.priority ] : PriorityString | Number
The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.
Defaults to
'normal'
Defaults to
{}
-
once( event, callback, [ options ] = { [options.priority] } )
module:engine/view/view~View#once
mixed
Registers a callback function to be executed on the next time the event is fired only. This is similar to calling
on
followed byoff
in the callback.Parameters
event : String
The name of the event.
callback : function
The function to be called on event.
[ options ] : Object
Additional options.
Properties[ options.priority ] : PriorityString | Number
The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.
Defaults to
'normal'
Defaults to
{}
-
scrollToTheSelection()
module:engine/view/view~View#scrollToTheSelection
Scrolls the page viewport and
domRoots
with their ancestors to reveal the caret, if not already visible to the user. -
set( name, [ value ] )
module:engine/view/view~View#set
mixed
Creates and sets the value of an observable property of this object. Such a property becomes a part of the state and is observable.
It accepts also 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 thatfoo.set( 'bar', 1 )
may be slightly slower thanfoo.bar = 1
.Parameters
name : String | Object
The property's name or object with
name=>value
pairs.[ value ] : *
The property's value (if
name
was passed in the first parameter).
-
stopDelegating( [ event ], [ emitter ] )
module:engine/view/view~View#stopDelegating
mixed
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 ofevent
to all emitters.
-
stopListening( [ emitter ], [ event ], [ callback ] )
module:engine/view/view~View#stopListening
mixed
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 fromemitter
.[ callback ] : function
(Requires the
event
) The function to be removed from the call list for the givenevent
.
-
unbind( [ unbindProperties ] )
module:engine/view/view~View#unbind
mixed
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 ] : String
Observable properties to be unbound. All the bindings will be released if no properties are provided.
-
_addEventListener( event, callback, [ options ] = { [options.priority] } )
module:engine/view/view~View#_addEventListener
protected mixed
Adds callback to emitter for given event.
Parameters
event : String
The name of the event.
callback : function
The function to be called on event.
[ options ] : Object
Additional options.
Properties[ options.priority ] : PriorityString | Number
The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.
Defaults to
'normal'
Defaults to
{}
-
_disableRendering( flag )
module:engine/view/view~View#_disableRendering
protected
Disables or enables rendering. If the flag is set to
true
then the rendering will be disabled. If the flag is set tofalse
and if there was some change in the meantime, then the rendering action will be performed.Parameters
flag : Boolean
A flag indicates whether the rendering should be disabled.
-
_removeEventListener( event, callback )
module:engine/view/view~View#_removeEventListener
protected mixed
Removes callback from emitter for given event.
Parameters
event : String
The name of the event.
callback : function
The function to stop being called.
-
_render()
module:engine/view/view~View#_render
private
Renders all changes. In order to avoid triggering the observers (e.g. selection) all observers are disabled before rendering and re-enabled after that.
Events
-
change:{property}( eventInfo, name, value, oldValue )
module:engine/view/view~View#event:change:{property}
mixed
Fired when a property changed value.
observable.set( 'prop', 1 ); observable.on( '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 : *
The new property value.
oldValue : *
The previous property value.
-
render( eventInfo )
module:engine/view/view~View#event:render
Fired after a topmost change block and all post-fixers are executed.
Actual rendering is performed as a first listener on 'normal' priority.
view.on( 'render', () => { // Rendering to the DOM is complete. } );
This event is useful when you want to update interface elements after the rendering, e.g. position of the balloon panel. If you wants to change view structure use post-fixers.
Parameters
eventInfo : EventInfo
An object containing information about the fired event.
-
set:{property}( eventInfo, name, value, oldValue )
module:engine/view/view~View#event:set:{property}
mixed
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( '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( '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 : *
The new property value.
oldValue : *
The previous property value.
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