Function fz_intersect_rect 

pub unsafe extern "C" fn fz_intersect_rect(
    a: fz_rect,
    b: fz_rect,
) -> fz_rect

Compute intersection of two rectangles.

Given two rectangles, update the first to be the smallest
axis-aligned rectangle that covers the area covered by both
given rectangles. If either rectangle is empty then the
intersection is also empty. If either rectangle is infinite
then the intersection is simply the non-infinite rectangle.
Should both rectangles be infinite, then the intersection is
also infinite.