[GRASS-dev] lib/vask

[Glynn Clements]

Hamish wrote:

> > The selection of GCPs should probably be integrated with Michael's
> > i.points replacement.
> > 
> > Is there any reason why other forms of interaction (other than visual
> > selection of coordinates) would be necessary?
> 
> 
> Beyond the mouse, keyboard entry is needed. e.g. set a GCP to where
> lat/lon grid lines meet by marking "+" spot and keying in coordinates,
> or getting GCPs coords by travelling to a landmark with a good GPS.

Are you referring to entering one point with the mouse and the
corresponding point as numerical coordinates? I can see why that would
need to be interactive. Can that not be integrated with the i.points
replacement?

Essentially, to what extent is it possible to separate the entry of
GCPs and other parameters from the actual rectification? Ideally, you
want to have as much code as possible in a non-interactive core, with
interaction limited to the outermost layer.

> various [Confirm][Cancel] buttons are needed...

In most cases, it's preferable to execute operations without
confirmation and to provide an undo feature for dealing with mistakes. 

Confirmation should be reserved for cases where undo is either
impossible (e.g. permanent deletion of data or other irrevocable
actions) or impractical (e.g. if the operation will leave the
application unresponsive for an extended period).

Confirmation shouldn't be used solely because it's easier to implement
than undo.

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