Polyline origin position is not quite intuitive

Whenever a polyline is created the origin is set to the first coordenates you clicked, and if you edit this first vertex and change the overall size of the polyline this origin position does not change. So it´s easy to lose the graphic representation of what the polyline (x,y) position means (specially if you use the move tool, because that updates the polyline position).
Maybe is more intuitive to define the position of a polyline by the top left corner of the rectangle that surrounds it, and update if you edit the vertexes. Since the first vertex coordenates are always (0,0), you could parse it the same way, it´s just easier to understand what the polyline (x,y) position really is.
The same applies to the polygon tool.

Start by tracing how the polyline and polygon tools assign positions when shapes are created, moved, and resized. Compare the current first-vertex origin with the proposed surrounding-rectangle origin; done means vertex edits update the position consistently and moving the shape preserves the expected representation.