Function fz_transform_rect 

pub unsafe extern "C" fn fz_transform_rect(
    rect: fz_rect,
    m: fz_matrix,
) -> fz_rect

Apply a transform to a rectangle.

After the four corner points of the axis-aligned rectangle
have been transformed it may not longer be axis-aligned. So a
new axis-aligned rectangle is created covering at least the
area of the transformed rectangle.

transform: Transformation matrix to apply. See fz_concat,
fz_scale and fz_rotate for how to create a matrix.

rect: Rectangle to be transformed. The two special cases
fz_empty_rect and fz_infinite_rect, may be used but are
returned unchanged as expected.