/**
 * Swipe-Back Detector
 *
 * Detects native edge swipe-back / swipe-forward gestures (iOS Safari, Android
 * system back gesture) purely from touch event sequences. We deliberately do
 * NOT depend on popstate because:
 *
 *   - iOS 16+ has a regression (WebKit 248303) where swipe-back skips popstate
 *     when history entries were created without user interaction.
 *   - popstate doesn't tell us *how* the navigation happened — header back-button,
 *     keyboard shortcut, history.back() and edge-swipe all look identical.
 *
 * Heuristic
 *   1. touchstart with a single touch starting within EDGE_THRESHOLD px of either
 *      vertical edge of the layout viewport → record a candidate.
 *   2. touchmove that is horizontally dominant AND moves *away* from that edge
 *      by more than MOVE_THRESHOLD → mark candidate as "moved".
 *      Multi-touch, vertically-dominant motion, or losing the tracked finger all
 *      drop the candidate.
 *   3. touchend with cumulative |dx| ≥ FINAL_DISTANCE in the correct direction
 *      → settle as a swipe.
 *      touchcancel after horizontal commitment also counts: the browser took the
 *      gesture over, which is exactly what edge-swipe-back does on iOS.
 *      In some environments (notably iOS WKWebView), the OS commits the gesture
 *      and dispatches `touchend` instead of `touchcancel`, with `clientX`
 *      reported in the now document-translated coordinate space — `dx` flips
 *      sign and fails the in-direction recheck above. When the in-direction
 *      check fails but `|dx| ≥ FINAL_DISTANCE` and `moved` was set during
 *      touchmove, treat it as the same takeover signal: the magnitude survives
 *      translation, while keeping the FINAL_DISTANCE floor rejects weak or
 *      cancelled gestures, matching pre-patch behavior in normal browsers.
 *
 * Settling arms an "active" flag. The flag auto-expires after EXPIRE_WINDOW so
 * a successful gesture that wasn't actually a navigation (e.g. user dragged a
 * right-anchored sheet) doesn't poison subsequent navigations.
 *
 * The flag also has a `stickyActive` mirror that lives one extra macrotask past
 * `onPageEnter()`, so an OUT/IN pair queued together (which can fire in either
 * order across adapters) reads the same value.
 *
 * Mac trackpad and Magic Trackpad swipes don't dispatch touch events on web, so
 * they go unhandled here. That's intentional — we'd rather miss-detect those
 * than false-positive them.
 */
export declare function createSwipeBackDetector(): {
    initialize: () => void;
    destroy: () => void;
    isSwipeBack: () => boolean;
    onPageEnter: () => void;
};
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