/**
 * @packageDocumentation
 *
 * Helpers for working with HTML elements.
 */
/**
 * A HTML element that can be validated.
 */
export interface ValidatorElement extends HTMLElement {
    /**
     * Checks the validity of the element.
     *
     * @returns True if the element is valid, false otherwise.
     */
    checkValidity(): boolean;
    /**
     * Reports the validity of the element.
     */
    reportValidity(): boolean;
    /**
     * Sets a custom error message on the element.
     *
     * @param error - The error message to set on the element.
     */
    setCustomValidity(error: string): void;
    /**
     * The error message of the element.
     */
    readonly validationMessage: string;
}
/**
 * Appends a code block to the given DocumentFragment or HTMLElement.
 *
 * @param el - The DocumentFragment or HTMLElement to append the code block to.
 * @param code - The code to be displayed in the code block.
 */
export declare function appendCodeBlock(el: DocumentFragment | HTMLElement, code: string): void;
/**
 * Ensures that the given element is loaded.
 *
 * @param el - The element to ensure is loaded.
 * @returns A {@link Promise} that resolves when the element is loaded.
 */
export declare function ensureLoaded(el: Element): Promise<void>;
/**
 * Checks if the element is visible in the offset parent.
 *
 * @param el - The element to check.
 * @returns True if the element is visible in the offset parent, false otherwise.
 */
export declare function isElementVisibleInOffsetParent(el: HTMLElement): boolean;
/**
 * Checks if the element is loaded.
 *
 * @param el - The element to check.
 * @returns True if the element is loaded, false otherwise.
 */
export declare function isLoaded(el: Element): boolean;
/**
 * Adds an event listener to the ancestor nodes of the given node.
 *
 * @param node - The node to add the event listener to.
 * @param callback - The callback to call when the event is triggered.
 * @returns A function to remove the event listener.
 */
export declare function onAncestorScrollOrResize(node: Node, callback: () => void): () => void;
/**
 * Converts a number to a string with 'px' appended.
 *
 * @param value - The number to convert.
 * @returns The number as a string with 'px' appended.
 */
export declare function toPx(value: number): string;