/**
 * Paints one colour through a coverage mask, over the box the mask was drawn
 * in.
 *
 * A stroke whose own bands overlap cannot be composited band by band: two
 * antialiased fringes landing on one pixel compose to more than the union
 * canvas fills once, which reads as a dark seam at every joint. The bands go
 * into the mask first, where the pass keeps the largest value on each pixel,
 * and this draws the result in a single composite.
 *
 * The mask is single sampled and the frame may not be, so the coverage is read
 * by whole texel at the pixel centre rather than sampled.
 */
export declare const maskCompositeShader: (blend: string) => string;