import { SimpleEventDispatcher } from './EventDispatcher';
import { IDisposable } from './types';
/**
 * A helper class to handle pointer events and dispatch drag events: `drag`, `dragStart` and `dragEnd` with NDC coordinates and time.
 *
 * To use, create an object of the class, set `element` with the HTML element(like canvas) and add event listeners to drag events.
 *
 * @example
 * ```ts
 * const pointerDragHelper = new PointerDragHelper()
 * pointerDragHelper.element = canvas
 * pointerDragHelper.addEventListener('dragStart', (e) => {
 *    console.log('dragStart', e.pointer)
 *    // {x: -0.5, y: 0.5, time: 123456789}
 *    // x and y are NDC coordinates, time is the time when the event is fired.
 *    // x and y are in the range of [-1, 1].
 *    // x is left to right, y is bottom to top.
 *    // time is in milliseconds.
 * })
 * pointerDragHelper.addEventListener('drag', (e) => {
 *   console.log('drag', e.pointer)
 *   // {x: -0.5, y: 0.5, time: 123456789}
 * })
 * pointerDragHelper.addEventListener('dragEnd', (e) => {
 *  console.log('dragEnd', e.pointer)
 *  // {x: -0.5, y: 0.5, time: 123456789}
 * })
 * ```
 */
export declare class PointerDragHelper extends SimpleEventDispatcher<'dragStart' | 'drag' | 'dragEnd'> implements IDisposable {
    private _pointerDown?;
    private _pointer?;
    private _pointerUp?;
    get element(): HTMLElement | undefined;
    set element(value: HTMLElement | undefined);
    private _element?;
    private _removeElement;
    private _addElement;
    private _onPointerDown;
    private _onPointerMove;
    private _onPointerUp;
    dispose(): void;
}
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