The label indicating the horizontal drag and full span is now located
at the proper location be the integration scope 1D or 2D, either
rectangle or rhomboid. Feature-full stuff.

even though these two functions actually return m_point (one-dimensional scope).

For testing purposes, write on the graph both the full x/y span and the mere x/y delta.

For rhomboid integration scopes make the difference between width / height and rhomb horizontal/vertical sizes.