Construct the smallest rectangle that encloses the given offsets, treating them as vectors from the origin.
Source
Rect.fromPoints(Offset a, Offset b) { _value ..[0] = math.min(a.dx, b.dx) ..[1] = math.min(a.dy, b.dy) ..[2] = math.max(a.dx, b.dx) ..[3] = math.max(a.dy, b.dy); }