/**
 * Pure math for edge-swipe navigation. No DOM, no React — unit-tested in
 * `src/chrome/__tests__/swipeMath.test.ts`.
 */
export type SwipeDirection = "back" | "forward";
/**
 * Decide whether a touch at `x` starts an edge swipe, and in which direction.
 * `back` = left edge, `forward` = right edge (iOS only — pass
 * `allowForward: false` on Android, whose right edge belongs to the system
 * back gesture).
 */
export declare function shouldStartSwipe(x: number, innerWidth: number, edgeWidth: number, allowForward: boolean): SwipeDirection | null;
/**
 * Drag progress 0..1. `back` grows as the finger moves right from the left
 * edge; `forward` grows as it moves left from the right edge. Clamped; motion
 * against the gesture direction is 0.
 */
export declare function computeProgress(startX: number, x: number, innerWidth: number, dir: SwipeDirection): number;
/**
 * Commit the navigation when the finger travelled far enough (`ratio` of the
 * viewport) OR was flicked fast enough (`velocity` in px/ms along the gesture
 * direction).
 */
export declare function shouldCommit(progress: number, velocity: number, ratio: number, velocityThreshold: number): boolean;
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