[GRASS-PSC] RFC: Module Option Parser

[Brad Douglas]

I'm in the process of updating/upgrading the imagery libraries and
modules.  I have run into a problem which I wish to simplify, but would
require modification of lib/gis/parser.c, etc.

I think we can all agree that i.ortho.photo is a mess and hasn't been
able to evolve as the rest of GRASS has.  I want to remove as much
interactivity as possible, but that creates a dilemma:

A) I can break i.ortho.photo into 7-8 separate modules, or
B) I can make it a single module by using the following structure:

Option A does not set well with me and Markus has agreed, privately, due
to the ever growing list of GRASS modules, so I need something a bit
'better'.

- Create an Option that allows to select from a series of commands like
v.build does:

    tool_opt = G_define_option ();
    tool_opt->key         = "tool";
    tool_opt->type        = TYPE_STRING;
    tool_opt->required    = YES;
    tool_opt->multiple    = NO;
    tool_opt->description = _("The ortho tool to use:\n"
                "\t\ttarget    - Target imagery location and mapset\n"
                "\t\tdem       - Digital Elevation Model (elevation)\n"
                "\t\tcamera    - Camera parameters\n"
                "\t\ttransform - Transformation parameters\n"
                "\t\texposure  - Exposure parameters\n"
                "\t\tparams    - Ortho photo parameters\n"
                "\t\trectify   - Rectify the ortho photo");
    tool_opt->options     =
"target,dem,camera,transform,exposure,params,rectify";

...but alter it a bit, namely changing the first line to:
tool_opt = G_define_selection(), a new function.

In order to make this work and keep the many options from spamming
i.ortho.photo --help (as many of the above selections have multiple
options that are not related to each other), I would like to propose the
following changes:

- Create a new function: G_define_selection ();
- Add another option to G_define_option () that would link an option to
a selection:
    dem_opt = G_define_option ();
    dem_opt->key           = "dem";
    dem_opt->type          = TYPE_STRING;
    dem_opt->required      = NO;
    dem_opt->multiple      = NO;
    dem_opt->description   = _("Digital Elevation Model");
--> dem_opt->selection     = "dem";   <--- new option

So...when I do 'i.ortho.photo --help', I get a list of selections to
choose from.  When I do, 'i.ortho.photo select=dem --help', I only get a
list of options associated with the "dem" selection (ie. dem_opt).

Comments, suggestions, and better ideas are always welcome.


-- 
Brad Douglas <rez touchofmadness com>                    KB8UYR/6
Address: 37.493,-121.924 / WGS84    National Map Corps #TNMC-3785