/**
 * Helpers for the html-in-canvas wrapper canvas.
 *
 * Chrome has shipped two markups for it:
 * - `<canvas layoutsubtree>` (Chrome ≤ 156);
 * - `<canvas content="drawable">` with a `drawable` attribute on each child
 *   to draw (Chrome 159+, where `layoutsubtree` alone no longer paints).
 *
 * We set both so the same wrapper works in either version.
 */
/** True if `el` is a canvas that captures its children with drawElementImage. */
export declare function isHicCanvas(el: Element): el is HTMLCanvasElement;
/** Mark `canvas` as an html-in-canvas wrapper and `child` as drawable. */
export declare function markHicCanvas(canvas: HTMLCanvasElement, child?: Element | null): void;
/** The parts of a DOMRect we use. */
export type RectLike = {
    left: number;
    top: number;
    width: number;
    height: number;
};
/**
 * Where to draw a nested canvas into the capture buffer.
 *
 * `base` is the captured element's rect, `rect` the nested canvas's content
 * box (both in CSS px, viewport coords). `sx` / `sy` are capture buffer px
 * per CSS px. Returns null when the canvas is empty or outside `base`.
 */
export declare function nestedCanvasDest(base: RectLike, rect: RectLike, sx: number, sy: number): [number, number, number, number] | null;
/**
 * Draw each visible canvas inside `root` over the capture at its layout
 * size and position. Works around Chrome drawing nested canvases at buffer
 * size and clipping them. It draws on
 * top of everything else, so an
 * element stacked above a canvas is hidden by it, and a canvas with
 * transparent pixels shows the wrongly sized copy through them.
 */
export declare function redrawNestedCanvases(ctx: CanvasRenderingContext2D, root: Element): void;