/**
 * ScrollTrigger
 *
 * Triggers timelines based on scroll position:
 * - start/end parameters define trigger zone (GSAP-style)
 * - scrub links animation progress to scroll position
 * - scrub: number adds smooth lag (in seconds)
 * - scroller: custom scroll container (default: window)
 * - pin: fix element in place during animation
 * - markers shows debug markers (optional)
 *
 * Pin implementation:
 * - Window scroller: uses position:fixed (seamless, no jitter)
 * - Custom scroller: uses transform (slight lag unavoidable)
 *
 * Start/End format: "<element_position> <scroller_position>"
 * - Keywords: top, center, bottom
 * - Units: 100px, 50%, 20vh
 * - Relative: +=500px (for end only)
 */
import type { ScrollConfig } from '../types';
import type { Timeline } from '../core/Timeline';
import { BaseTrigger } from './BaseTrigger';
export declare class ScrollTrigger extends BaseTrigger<ScrollConfig> {
    private static _nextId;
    private _id;
    private static readonly _SCRUB_TICKER_PRIORITY;
    private static readonly _TINY_RANGE_PX;
    private static _activeInstances;
    private static _loadListenerAdded;
    private _scrollListener?;
    private _scrubTickListener;
    private _currentProgress;
    private _targetProgress;
    private _scrubLag;
    private _scroller;
    private _triggerStart;
    private _triggerEnd;
    private _pinManager;
    private _markerManager;
    private _triggerState;
    private _toggleActions;
    private _initializing;
    constructor(timeline: Timeline, config: ScrollConfig);
    /**
     * Register the global window.load listener (once).
     * After all resources finish loading, refresh every active ScrollTrigger
     * so trigger positions account for layout shifts caused by images/fonts.
     */
    private static _ensureLoadListener;
    private _resolveScroller;
    private _resolvePinElement;
    /**
     * Default start position — matches GSAP behavior:
     * - With pin:    'top top'    (element top hits viewport top)
     * - Without pin: 'top bottom' (element top hits viewport bottom)
     */
    private _defaultStart;
    /**
     * Default end position — matches GSAP behavior:
     * 'bottom top' (element bottom hits viewport top)
     */
    private _defaultEnd;
    private _getFirstAnimatedElement;
    /**
     * Resolve the trigger element from config or first animation
     */
    private _resolveTriggerElement;
    /**
     * Resolve the element the `end` position is measured against (GSAP `endTrigger`
     * parity). Returns null when no `endTarget` is configured or it matches nothing,
     * in which case `end` is measured against the start/trigger element — the
     * default GSAP behaviour.
     */
    private _resolveEndTargetElement;
    /**
     * Calculate trigger start/end scroll positions based on config.
     *
     * Pin distance equals the trigger range (triggerEnd - triggerStart).
     * The PinManager spacer adds exactly that many pixels of scroll room to the
     * page, so the animation always plays over the full configured distance while
     * the element is pinned — no separate "extension" step is needed.
     *
     * When refresh() is called while the element is position:fixed (pinned), we
     * use the spacer's rect instead of the element's rect.  A position:fixed
     * element returns viewport-relative coordinates from getBoundingClientRect(),
     * which would produce incorrect document-relative trigger positions.  The
     * spacer sits in the element's original place in the document flow, so its
     * rect always reflects the correct base for the calculation.
     */
    private _calculateTriggerPositions;
    protected _onEnable(): void;
    protected _onDisable(): void;
    /**
     * Refresh trigger positions (call after layout changes like resize)
     */
    refresh(): void;
    private _getViewportHeight;
    private _getScrollTop;
    private _getScrollHeight;
    private _onScroll;
    /**
     * Apply snap to a raw progress value based on config.snap.
     * - number: snap to evenly-spaced increments (e.g. 0.25 → 0, 0.25, 0.5, 0.75, 1)
     * - number[]: snap to nearest value in array
     * - function: custom snap function
     */
    private _applySnap;
    private _startSmoothScrollLoop;
    private _stopSmoothScrollLoop;
}