[GRASS-dev] V.edit and GUI digitizing

[Glynn Clements]

Michael Barton wrote:

> V.edit, as currently prototyped involves transforming a set of xy
> coordinates into  vector objects. This is an important part of a digitizing
> system, but not all of it. Because we will  also want to edit existing
> vectors, there needs to be a way to transform vector objects into a set of
> xy coordinates, while preserving any needed topological and key field
> information to reconstruct them. In a discussion between Glynn and Radim
> recently, it became clear that v.out.ascii does most of this, but not
> all‹primarily lacking the topological information.
> 
> So in addition to v.edit, we¹ll need some kind of module to get relevant
> vector information OUT of an existing vector, and into a format that can be
> read by a GUI and v.edit.

The notion of "relevant" information would need to include omitting
any data which isn't relevant to the active region. It would still
need to include vertices which are themselves outside of the region
but which form part of a line or area which intersects the region.

There's also the issue that you probably don't want to have to
re-import everything into the GUI whenever anything is changed.

v.digit makes extensive use of Vect_get_updated_line(). I don't know
how this works; if it's client-side (i.e. the "updated" state isn't
stored in the map, only in the client process), the tool used to
perform the updates (v.edit) would have to be responsible for
reporting the updates to the GUI.

-- 
Glynn Clements <glynn at gclements.plus.com>