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, 17 insertions, 8 deletions

diff --git a/src/til_settings.h b/src/til_settings.h
index 935aa5b..52535fe 100644
--- a/src/til_settings.h
+++ b/src/til_settings.h
@@ -3,6 +3,9 @@
 
 #include <stdio.h>
 
+typedef struct til_setting_t til_setting_t;
+typedef struct til_settings_t til_settings_t;
+
 /* Individual setting description */
 typedef struct til_setting_desc_t {
 	const char	*name;		/* long-form/human name for setting */
@@ -18,21 +21,27 @@ typedef struct til_setting_desc_t {
 typedef struct til_setting_desc_generator_t {
 	const char	*key;		/* key this generator applies to */
 	const char	**value_ptr;	/* where to put the value */
-	int		(*func)(void *setup_context, til_setting_desc_t **res_desc);
+	int		(*func)(void *setup_context, const til_setting_desc_t **res_desc);
 } til_setting_desc_generator_t;
 
-typedef struct til_settings_t til_settings_t;
+/* Encapsulates a single til_settings_t entry */
+struct til_setting_t {
+	const char			*key;
+	const char			*value;
+	const til_setting_desc_t	*desc;
+};
 
 til_settings_t * til_settings_new(const char *settings);
 til_settings_t * til_settings_free(til_settings_t *settings);
-const char * til_settings_get_value(const til_settings_t *settings, const char *key);
-const char * til_settings_get_key(const til_settings_t *settings, unsigned pos);
-int til_settings_add_value(til_settings_t *settings, const char *key, const char *value);
+const char * til_settings_get_value(const til_settings_t *settings, const char *key, const til_setting_t **res_setting);
+const char * til_settings_get_key(const til_settings_t *settings, unsigned pos, const til_setting_t **res_setting);
+int til_settings_add_value(til_settings_t *settings, const char *key, const char *value, const til_setting_desc_t *desc);
+int til_settings_get_and_describe_value(const til_settings_t *settings, const til_setting_desc_t *desc, const char **res_value, const til_setting_t **res_setting, const til_setting_desc_t **res_desc);
 char * til_settings_as_arg(const til_settings_t *settings);
-int til_settings_apply_desc_generators(const til_settings_t *settings, const til_setting_desc_generator_t generators[], unsigned n_generators, void *setup_context, til_setting_desc_t **next_setting);
+int til_settings_apply_desc_generators(const til_settings_t *settings, const til_setting_desc_generator_t generators[], unsigned n_generators, void *setup_context, const til_setting_t **res_setting, const til_setting_desc_t **res_desc);
 
-int til_setting_desc_clone(const til_setting_desc_t *desc, til_setting_desc_t **res_desc);
-til_setting_desc_t * til_setting_desc_free(til_setting_desc_t *desc);
+int til_setting_desc_clone(const til_setting_desc_t *desc, const til_setting_desc_t **res_desc);
+til_setting_desc_t * til_setting_desc_free(const til_setting_desc_t *desc);
 int til_setting_desc_check(const til_setting_desc_t *desc, const char *value);
 
 #ifndef TIL_SETTINGS_STR