Function intersectClip

src/ink/output.ts:104–112

* Intersect two clips. `undefined` on an axis means unbounded; the other * clip's bound wins. If both are bounded, take the tighter constraint * (max of mins, min of maxes). If the resulting region is empty * (x1 >= x2 or y1 >= y2), writes clipped by it will be dropped.

(parent: Clip | undefined, child: Clip)

 * (x1 >= x2 or y1 >= y2), writes clipped by it will be dropped.
 */
function intersectClip(parent: Clip | undefined, child: Clip): Clip {
  if (!parent) return child
  return {
    x1: maxDefined(parent.x1, child.x1),
    x2: minDefined(parent.x2, child.x2),
    y1: maxDefined(parent.y1, child.y1),
    y2: minDefined(parent.y2, child.y2),
  }
}

function maxDefined(
  a: number | undefined,