/**
* @license Copyright (c) 2003-2026, CKSource Holding sp. z o.o. All rights reserved.
* For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-licensing-options
*/
/**
* A helper class which instances allow performing custom actions when native DOM elements are resized.
*
* ```ts
* const editableElement = editor.editing.view.getDomRoot();
*
* const observer = new ResizeObserver( editableElement, entry => {
* 	console.log( 'The editable element has been resized in DOM.' );
* 	console.log( entry.target ); // -> editableElement
* 	console.log( entry.contentRect.width ); // -> e.g. '423px'
* } );
* ```
*
* It uses the [native DOM resize observer](https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserver)
* under the hood.
*/
export declare class ResizeObserver {
	/**
	* The element observed by this observer.
	*/
	private readonly _element;
	/**
	* The callback executed each time {@link #_element} is resized.
	*/
	private readonly _callback;
	/**
	* The single native observer instance shared across all {@link module:utils/dom/resizeobserver~ResizeObserver} instances.
	*/
	private static _observerInstance;
	/**
	* A mapping of native DOM elements and their callbacks shared across all
	* {@link module:utils/dom/resizeobserver~ResizeObserver} instances.
	*/
	private static _elementCallbacks;
	/**
	* Creates an instance of the `ResizeObserver` class.
	*
	* @param element A DOM element that is to be observed for resizing. Note that
	* the element must be visible (i.e. not detached from DOM) for the observer to work.
	* @param callback A function called when the observed element was resized. It passes
	* the [`ResizeObserverEntry`](https://developer.mozilla.org/en-US/docs/Web/API/ResizeObserverEntry)
	* object with information about the resize event.
	*/
	constructor(element: Element, callback: (entry: ResizeObserverEntry) => void);
	/**
	* The element observed by this observer.
	*/
	get element(): Element;
	/**
	* Destroys the observer which disables the `callback` passed to the {@link #constructor}.
	*/
	destroy(): void;
	/**
	* Registers a new resize callback for the DOM element.
	*/
	private static _addElementCallback;
	/**
	* Removes a resize callback from the DOM element. If no callbacks are left
	* for the element, it removes the element from the native observer.
	*/
	private static _deleteElementCallback;
	/**
	* Returns are registered resize callbacks for the DOM element.
	*/
	private static _getElementCallbacks;
	/**
	* Creates the single native observer shared across all `ResizeObserver` instances.
	*/
	private static _createObserver;
}