[GRASSGUI] wxgrass: histogram and profile

[Glynn Clements]

Markus Neteler wrote:

> > > # concering distance measure:
> > > I feel that the result in latlong is degree or so - could this be changed
> > > to metric output (like d.measure does with G_begin_distance_calculations())?
> > 
> > This is a very good idea. But how can we get distance in meters from the
> > map? Anyone?
> 
> libgis offers such function (see d.histogram). Time to get the
> SWIG interface working :)

I would advise against using libgis (via SWIG) in the GUI. The design
of libgis is entirely unsuited to persistent applications.

For example:

1. G_begin_distance_calculations() obtains the projection using
G_projection().

2. G_projection() obtains the current window using G_get_set_window(),
and returns the projection field.

3. G_get_set_window() returns G__.window, after calling
G__init_window() to initialise it.

4. G__init_window() calls G_get_window() if the window isn't already
set. If it is set, it does nothing.

If the GUI changes locations while running, the distance functions
would continue using the original projection, unless you manually
reset G__.window. And you can't use G_get_window() to read the WIND
file etc, as that just returns G__.window once it has been set.

More generally, there are just too many variables which get
initialised once and cannot subsequently be reset. This isn't a
problem for normal modules, but it's a fundamental problem for a GUI.

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