/**
 * Small-screen / portrait viewport strategy (#215).
 *
 * The shell is authored against a fixed baseline (1024×768). On a container that
 * can't fit it — a phone — we render at the baseline and CSS-scale the whole
 * stage to fit, letterboxed, so nothing reflows (fidelity is the product spine;
 * the decision record is `docs/VIEWPORT.md`). This hook owns the policy → scale
 * resolution only; it is engine-pure (no styling, no color). The letterbox and
 * the `transform` live in the view layer.
 */
export type ViewportPolicy = 'auto' | 'scale' | 'native' | 'warn';
/** The XP baseline the shell is designed against. */
export declare const VIEWPORT_BASE_WIDTH = 1024;
export declare const VIEWPORT_BASE_HEIGHT = 768;
export interface ViewportScale {
    /** Whether a scale transform should be applied (false ⇒ the untouched layout). */
    active: boolean;
    /** The scale factor (1 when inactive). */
    scale: number;
    baseWidth: number;
    baseHeight: number;
    orientation: 'portrait' | 'landscape';
    /** Portrait + scaled — landscape would scale larger, so nudge to rotate. */
    showRotateHint: boolean;
}
export declare function useViewportScale(policy?: ViewportPolicy, containerRef?: React.RefObject<HTMLElement>): ViewportScale;