/**
 * This Source Code is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright (c) Infonomic Company Limited
 */
/**
 * Pure state for click-and-drag scrolling of the tab strip.
 *
 * The DOM plumbing — pointer capture, the click suppression, the cursor —
 * lives in `tabs.tsx`; the rules it follows are here so they can be tested
 * without a pointer.
 */
/**
 * How far the pointer must travel before the gesture stops being a click and
 * becomes a drag.
 *
 * Without a threshold every click on a tab would nudge the strip by a pixel or
 * two, and the click suppression that follows a drag would swallow the very
 * clicks that select tabs.
 */
export declare const DRAG_THRESHOLD_PX = 5;
/**
 * How long after a drag a click is treated as that drag's own click.
 *
 * A window rather than a consume-once flag, because the click is not
 * guaranteed to arrive: a drag released outside the strip produces none, and
 * a flag left armed would swallow the reader's next deliberate click on a tab.
 * Far longer than the browser's synthetic click takes to arrive, far shorter
 * than anyone can release and deliberately click again.
 */
export declare const CLICK_SUPPRESSION_MS = 100;
/** Where a gesture began. An internal part of `DragState`, not a public type. */
interface DragOrigin {
    /** Pointer x at the moment the button went down. */
    pointerX: number;
    /** The viewport's scroll offset at that same moment. */
    scrollLeft: number;
}
export interface DragState {
    origin: DragOrigin;
    /** Whether the threshold has already been crossed. */
    dragging: boolean;
}
export interface DragAdvance {
    dragging: boolean;
    /** The offset to scroll to, or `null` while the gesture is still a click. */
    scrollLeft: number | null;
}
/**
 * Whether a `pointerdown` should begin a potential drag.
 *
 * Mouse only. Touch and pen already scroll the viewport natively, with
 * momentum and rubber-banding that a hand-rolled drag does not reproduce, so
 * taking the gesture over would trade a good interaction for a worse one.
 */
export declare function shouldStartDrag({ pointerType, button, overflowing, }: {
    pointerType: string;
    button: number;
    overflowing: boolean;
}): boolean;
/**
 * Advance a gesture given the pointer's current x.
 *
 * Returns `scrollLeft: null` while the pointer is still within the threshold,
 * so the caller leaves the viewport alone and lets the click through.
 */
export declare function advanceDrag({ origin, dragging }: DragState, pointerX: number, maxScroll: number): DragAdvance;
/**
 * Whether a click arriving now belongs to a drag that has just ended, and
 * should therefore not reach the tab underneath.
 */
export declare function shouldSuppressClick(dragEndedAt: number | null, now: number): boolean;
export {};