Rework of hooks adding

src/libslic3r/Line.cpp

@@ -100,6 +100,13 @@ bool Line::clip_with_bbox(const BoundingBox &bbox)
 	return result;
 }
 
+void Line::offset(double offset)
+{
+    Vector offset_vector = (offset * this->vector().cast<double>().normalized()).cast<coord_t>();
+    this->a -= offset_vector;
+    this->b += offset_vector;
+}
+
 Vec3d Linef3::intersect_plane(double z) const
 {
     auto   v = (this->b - this->a).cast<double>();