export declare const GLASS_LENS_ID = "cds-glass-lens";
/** The material's backdrop-filter while a surface's sized def is not ready
 *  yet (first frame before layout): the lens's own blur + saturation grade,
 *  so the swap to the sized def only adds the rim bend. */
export declare const GLASS_LENS_PENDING_FILTER = "blur(6px) saturate(190%)";
/** The displacement-map image for a w x h surface, as a data URI. Exported for
 *  tests, which assert the band geometry instead of eyeballing pixels. */
export declare function lensMapDataUri(w: number, h: number, rimX: number, rimY: number, rx: number, ry: number): string;
/** One filter primitive: its tag and its attributes. */
export interface LensNode {
    tag: string;
    attrs: Record<string, string | number>;
}
/** A whole `<filter>` def: the filter's own attributes plus its primitives. */
export interface LensFilterSpec {
    attrs: Record<string, string | number>;
    children: LensNode[];
}
/** The shared CSS-token def's spec: the blur + saturation grade with NO
 *  displacement (see the header for why it cannot carry one). Pure. */
export declare function sharedLensFilterSpec(id: string): LensFilterSpec;
/** The full sized-filter spec. Pure and exported for tests. */
export declare function sizedLensFilterSpec(id: string, w: number, h: number): LensFilterSpec;
/** True when the shared (CSS-token) lens def is present in this document. */
export declare function hasGlassLens(): boolean;
/** Inject the shared `#cds-glass-lens` def the CSS token layer points at:
 *  blur + saturation only (see the header for why it carries no displacement).
 *  Idempotent; returns whether the def is now available. */
export declare function ensureGlassLens(): boolean;
/** Acquire (create if absent) the sized lens def for a w x h surface. Returns
 *  its key and url, or null when no document is available. Pair every acquire
 *  with a release. */
export declare function acquireSizedGlassLens(w: number, h: number): {
    key: string;
    url: string;
} | null;
/** Release a def acquired with acquireSizedGlassLens; the def is removed from
 *  the document when its last holder releases it. */
export declare function releaseSizedGlassLens(key: string): void;
/** Test hook: the number of live sized defs. */
export declare function sizedGlassLensCount(): number;
/**
 * Whether this engine can RENDER an SVG-reference backdrop-filter, decided from
 * the user agent string and a `CSS.supports` probe. Only Chromium renders SVG
 * filters in `backdrop-filter`; WebKit and Gecko parse-accept the value but
 * paint no filter at all, which would strip the frost instead of upgrading it,
 * and with a single inline style value there is no CSS-cascade fallback to
 * catch that. Render support is therefore not feature-detectable, and the gate
 * allows the known-good family: every Chromium UA carries "Chrome/" (Edge,
 * Brave, Arc, Opera, HeadlessChrome included), while iOS Chrome, which is
 * WebKit underneath, identifies as "CriOS/" and correctly stays on the frost.
 * The `CSS.supports` probe is the future-proof floor for engines that reject
 * the value outright. Pure so tests can exercise the truth table directly.
 */
export declare function lensBackdropSupported(userAgent: string, supports: (property: string, value: string) => boolean): boolean;
/**
 * The lens gate for a glass surface: true only where a document exists and the
 * engine can render SVG-reference backdrop-filters (Chromium web). The lens
 * layer itself acquires its sized def on layout; until then it renders the
 * pending blur + saturate grade, never a reference to a missing filter, which
 * would resolve to NO filter at all.
 */
export declare function useGlassLens(glass: boolean): boolean;
/**
 * The sized-def lifecycle for one lens layer: feed it the layer's layout size,
 * get the backdrop-filter value to render. Acquires the def for the current
 * size, swaps on resize, releases on unmount, and returns the pending grade
 * until the def exists.
 */
export declare function useSizedGlassLens(width: number, height: number): string;
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