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, 22 insertions, 24 deletions

diff --git a/src/modules/submit/submit.c b/src/modules/submit/submit.c
index 288a69a..d643a2c 100644
--- a/src/modules/submit/submit.c
+++ b/src/modules/submit/submit.c
@@ -322,32 +322,30 @@ static void submit_render_fragment(void *context, unsigned ticks, unsigned cpu,
 }
 
 
-static int submit_setup(const til_settings_t *settings, til_setting_desc_t **next_setting)
+static int submit_setup(const til_settings_t *settings, const til_setting_t **res_setting, const til_setting_desc_t **res_desc)
 {
+	const char	*values[] = {
+				"off",
+				"on",
+				NULL
+			};
 	const char	*bilerp;
-
-	bilerp = til_settings_get_value(settings, "bilerp");
-	if (!bilerp) {
-		const char	*values[] = {
-					"off",
-					"on",
-					NULL
-				};
-		int		r;
-
-		r = til_setting_desc_clone(&(til_setting_desc_t){
-						.name = "Bilinear Interpolation of Cell Colors",
-						.key = "bilerp",
-						.regex = NULL,
-						.preferred = values[0],
-						.values = values,
-						.annotations = NULL
-					}, next_setting);
-		if (r < 0)
-			return r;
-
-		return 1;
-	}
+	int		r;
+
+	r = til_settings_get_and_describe_value(settings,
+						&(til_setting_desc_t){
+							.name = "Bilinear Interpolation of Cell Colors",
+							.key = "bilerp",
+							.regex = NULL,
+							.preferred = values[0],
+							.values = values,
+							.annotations = NULL
+						},
+						&bilerp,
+						res_setting,
+						res_desc);
+	if (r)
+		return r;
 
 	if (!strcasecmp(bilerp, "on"))
 		bilerp_setting = 1;