til_settings: always describe relevant settings

The existing iterative *_setup() interface only described
settings not found, quietly accepting usable settings already
present in the til_settings_t.

This worked fine for the existing interactive text setup thing,
but it's especially problematic for providing a GUI setup
frontend.

This commit makes it so the *_setup() methods always describe
undescribed settings they recognize, leaving the setup frontend
loop calling into the *_setup() methods to both apply the
description validation if wanted and actually tie the description
to respective setting returned by the _setup() methods as being
related to the returned description.

A new helper called til_settings_get_and_describe_value() has
been introduced primarily for use of module setup methods to
simplify this nonsense, replacing the til_settings_get_value()
calls and surrounding logic, but retaining the til_setting_desc_t
definitions largely verbatim.

This also results in discarding of some ad-hoc
til_setting_desc_check() calls, now that there's a centralized
place where settings become "described" (setup_interactively in
the case of rototiller).

Now a GUI frontend (like glimmer) would just provide its own
setup_interactively() equivalent for constructing its widgets for
a given *_setup() method's chain of returned descs.  Whereas in
the past this wasn't really feasible unless there was never going
to be pre-supplied settings.

I suspect the til_setting_desc_check() integration into
setup_interactively() needs more work, but I think this is good
enough for now and I'm out of spare time for the moment.

1 files changed, 7 insertions, 4 deletions

diff --git a/src/til.c b/src/til.c
index 0989a6d..e69cade 100644
--- a/src/til.c
+++ b/src/til.c
@@ -165,12 +165,13 @@ int til_module_create_context(const til_module_t *module, unsigned ticks, void *
 
 
 /* select module if not yet selected, then setup the module. */
-int til_module_setup(til_settings_t *settings, til_setting_desc_t **next_setting)
+int til_module_setup(til_settings_t *settings, const til_setting_t **res_setting, const til_setting_desc_t **res_desc)
 {
+	const til_setting_t	*setting;
 	const til_module_t	*module;
 	const char		*name;
 
-	name = til_settings_get_key(settings, 0);
+	name = til_settings_get_key(settings, 0, &setting);
 	if (!name) {
 		const char		*values[nelems(modules) + 1] = {};
 		const char		*annotations[nelems(modules) + 1] = {};
@@ -189,10 +190,12 @@ int til_module_setup(til_settings_t *settings, til_setting_desc_t **next_setting
 						.preferred = DEFAULT_MODULE,
 						.values = values,
 						.annotations = annotations
-					}, next_setting);
+					}, res_desc);
 		if (r < 0)
 			return r;
 
+		*res_setting = name ? setting : NULL;
+
 		return 1;
 	}
 
@@ -201,7 +204,7 @@ int til_module_setup(til_settings_t *settings, til_setting_desc_t **next_setting
 		return -EINVAL;
 
 	if (module->setup)
-		return module->setup(settings, next_setting);
+		return module->setup(settings, res_setting, res_desc);
 
 	return 0;
 }