[GRASS-dev] grass is a monad?

[Radim Blazek]

On Mon, Jan 18, 2010 at 3:33 AM, Glynn Clements
<glynn at gclements.plus.com> wrote:
>> Everything except vector editing. I don't see any reasonable
>> possibility to do interactive vector editing via a GRASS module. For
>> vector editing, I need immediate response which is visualized on
>> display (e.g. if a vertex was moved and area topology was broken it
>> must be displayed). It is impossible to open/close a vector for every
>> single operation, it would take too long time for larger vectors.
>
> For this specific case, is it possible to isolate a subset of the
> vector library such that it can be used reasonably by both GRASS and
> QGIS (and the wxGUI's vdigit module, which is just as bad in this
> regard)?

The subset would be almost the whole vector library (Vlib,diglib,rtree).

> Also, what kind of fatal errors can occur while in the middle of
> vector editing that could reasonably be recovered from?

Probably I don't understand the question, for any error I would prefer
to give a decent message
(in window box) and stop editing (even with corrupted vector) but
don't crash the application.

> I'm not particularly averse to libraries using status returns, so long
> as this doesn't:
>
> 1. propagate up to the API used by modules,

So you would suggest a separate set of functions for modules and QGIS/vdigit?

> 2. "infest" a large portion of the GRASS libraries, or
> 3. mean that fatal errors end up being signalled at the highest levels
> after most of the context has been lost.

What is wrong on calling G_fatal_error on each level from the first
function where the error happened to the top and optionally  (i.e.
modules wants exit, qgis/vdigit return value) either only print the
message (call error routine) and return error code or exit (it means
on the lowest level).


Radim