# FullscreenAbstractEditorHandler
class
The abstract editor type handler.
This class defines some actions and behaviors that are applied when fullscreen mode is toggled, and which are common regardless of the editor type. Then, specific classes like `ClassicEditorHandler` or `DecoupledEditorHandler` extend this class with actions specific for these editor types.
Extend this class to provide fullscreen mode handling for unsupported editor types, or if you wish to heavily customize the default behavior.
The only method that is necessary to provide when extending this class is [`defaultOnEnter`](#function-defaultOnEnter). However, make sure to familiarize yourself with the below full list of actions taken by `FullscreenAbstractEditorHandler` to understand what is covered by default, and what should be provided by you.
When entering the fullscreen mode, the [`enable`](#function-enable) method is called. It creates the properly styled container and handles the editor features that need it, in the following order:
1. Saves the scroll positions of all ancestors of the editable element to restore them after leaving the fullscreen mode.
2. Executes the [`defaultOnEnter`](#function-defaultOnEnter) method to move the proper editor UI elements to the fullscreen mode. **If you extend the abstract handler, you should override this method** to move the elements that are specific to your editor type, like: editable, toolbar, menu bar. Use [`moveToFullscreen`](#function-moveToFullscreen) method for this purpose to ensure they are automatically cleaned up after leaving the fullscreen mode.
3. Adds proper classes to the `` and `` elements to block page scrolling, adjust `z-index` etc.
Steps 4-12 are only executed if the corresponding features are used.
4. If presence list is used, moves it to the fullscreen mode container.
5. If document outline is used, moves it to the fullscreen mode.
6. If pagination is used, adjusts it's configuration for the changed view.
7. If annotations are used, moves them to the fullscreen mode.
8. If revision history is used, overrides the callbacks to show the revision viewer in the fullscreen mode.
9. If AI Tabs is used, moves it to the fullscreen mode.
10. If source editing and document outline are both used, registers a callback hiding the document outline header in source editing mode.
11. Changes the position of some dialogs to utilize the empty space on the right side of the editable element.
12. If custom container is used, hides all other elements in it to ensure they don't create an empty unscrollable space.
Then finally:
13. Adjusts the visibility of the left and right sidebars based on the available space.
14. Sets up a resize observer to adjust the visibility of the left and right sidebars dynamically.
15. Executes the configured [`config.fullscreen.onEnterCallback`](module_fullscreen_fullscreenconfig-FullscreenConfig.md#member-onEnterCallback) function. By default, it returns the fullscreen mode container element so it can be further customized.
When leaving the fullscreen mode, the [`disable`](#function-disable) method is called. It does the following:
1. Execute the configured [`config.fullscreen.onLeaveCallback`](module_fullscreen_fullscreenconfig-FullscreenConfig.md#member-onLeaveCallback) function.
2. Remove the classes added to the `` and `` elements.
3. If document outline is used, restore its default container.
4. If annotations are used, restore their original state (UI, filters etc).
5. If revision history is used, restore the original callbacks.
6. If AI Tabs is used, restore it to the original state.
7. If source editing and document outline are both used, restore the document outline header.
8. Restore all moved elements to their original place.
9. Destroy the fullscreen mode container.
10. If the editor has a toolbar, switch its behavior to the one configured in the [`shouldGroupWhenFull`](module_ui_toolbar_toolbarview-ToolbarOptions.md#member-shouldGroupWhenFull) property.
11. Restore the scroll positions of all ancestors of the editable element.
12. If pagination is used, restore its default configuration.
13. Restore default dialogs positions.
This class is exported to allow for custom extensions.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L82)
## Properties
### `updateDialogPositionCallback: ( _evt: EventInfo, _name: string, isOpen: boolean ) => void`
Stores a bound reference to the \_updateDialogPosition method, allowing it to be attached and detached from change event.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L846)
### `_closeRevisionViewerCallback: ( viewerEditor: any ) => Promise | null` _(protected)_
A callback that closes the revision viewer, stored to restore the original one after exiting the fullscreen mode.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L178)
### `_editor: Editor & Partial` _(protected)_
An editor instance. It should be set by the particular editor type handler.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L183)
### `_showRevisionViewerCallback: ( config: EditorConfig ) => Promise | null` _(protected)_
A callback that shows the revision viewer, stored to restore the original one after exiting the fullscreen mode.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L173)
### `_aiTabsData: object | null` _(private)_
A map of AI Tabs data that were set before entering the fullscreen mode.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L188)
### `_annotationsUIsData: Map> | null` _(private)_
Data of the annotations UIs that were active before entering the fullscreen mode.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L101)
### `_disableContextualBalloonPositionHandler: VoidFunction` _(private)_
A cleanup function returned by `registerFullscreenBalloonOffsetCorrection`.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L144)
### `_document: Document` _(private)_
The document object in which the editor is located.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L96)
### `_hasLeftCollapseButton: boolean` _(private)_
Whether the left sidebar collapse button is created.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L112)
### `_hiddenElements: Map` _(private)_
A map of elements that were hidden when entering the fullscreen mode. It is used to restore their previous visibility when leaving the fullscreen mode and avoid showing elements that were hidden before entering the fullscreen mode.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L163)
### `_paginationBodyCollection: BodyCollection | null` _(private)_
The pagination body collection that is used in the fullscreen mode. If we don't move pagination lines to the fullscreen container, they won't be visible.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L107)
### `_placeholderMap: Map` _(private)_
Maps placeholder names to placeholder elements and moved elements.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L86)
### `_resizeObserver: ResizeObserver | null` _(private)_
The resize observer that is used to adjust the visibility of the left and right sidebars dynamically.
[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-fullscreen/src/handlers/abstracteditorhandler.ts#L122)