Pulls a box back inside the page: the origin is clamped to the page, then the extent is
clamped to what remains, so the result never runs past the right or bottom edge.
Coordinates stay in the stored space (top-left origin) — flip afterwards if drawing.
Does not reject non-finite input; run isDegenerateBox first.
Pulls a box back inside the page: the origin is clamped to the page, then the extent is clamped to what remains, so the result never runs past the right or bottom edge. Coordinates stay in the stored space (top-left origin) — flip afterwards if drawing. Does not reject non-finite input; run isDegenerateBox first.