/**
 * Resolves a CSS length value to a pixel number using a hidden DOM probe.
 *
 * Used by the JS positioning fallback: consumer offsets can be numbers,
 * `${n}px` strings, tokenised `var(--ds-space-100, 8px)` strings, `calc()`
 * expressions, viewport units, etc. Parsing arbitrary CSS in JS is fragile
 * (and impossible for `calc(var(...))` without a layout context), so we let
 * the browser do the math.
 *
 * The probe is appended to `container` so it inherits the same containing
 * block, font size, and custom-property scope as the popover.
 *
 * Cost: one synchronous reflow on first cacheable resolution per
 * (container, value) pair, then a `WeakMap` lookup. Resolutions involving
 * `var(` are intentionally not cached.
 */
export declare function resolveCssLengthToPixels({ value, container, }: {
    value: number | string;
    container: HTMLElement;
}): number;