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, 13 insertions, 10 deletions

diff --git a/src/main.c b/src/main.c
index a8a1988..776db85 100644
--- a/src/main.c
+++ b/src/main.c
@@ -56,13 +56,13 @@ typedef struct setup_t {
  */
 
 /* select video backend if not yet selected, then setup the selected backend. */
-static int setup_video(til_settings_t *settings, til_setting_desc_t **next_setting)
+static int setup_video(til_settings_t *settings, const til_setting_t **res_setting, const til_setting_desc_t **res_desc)
 {
-	const char	*video;
+	const til_setting_t	*setting;
+	const char		*video;
 
-	/* XXX: there's only one option currently, so this is simple */
-	video = til_settings_get_key(settings, 0);
-	if (!video) {
+	video = til_settings_get_key(settings, 0, &setting);
+	if (!video || !setting->desc) {
 		til_setting_desc_t	*desc;
 		const char		*values[] = {
 #ifdef HAVE_DRM
@@ -80,10 +80,13 @@ static int setup_video(til_settings_t *settings, til_setting_desc_t **next_setti
 						.preferred = DEFAULT_VIDEO,
 						.values = values,
 						.annotations = NULL
-					}, next_setting);
+					}, res_desc);
+
 		if (r < 0)
 			return r;
 
+		*res_setting = video ? setting : NULL;
+
 		return 1;
 	}
 
@@ -92,13 +95,13 @@ static int setup_video(til_settings_t *settings, til_setting_desc_t **next_setti
 	if (!strcmp(video, "drm")) {
 		fb_ops = &drm_fb_ops;
 
-		return drm_fb_ops.setup(settings, next_setting);
+		return drm_fb_ops.setup(settings, res_setting, res_desc);
 	} else
 #endif
 	if (!strcmp(video, "sdl")) {
 		fb_ops = &sdl_fb_ops;
 
-		return sdl_fb_ops.setup(settings, next_setting);
+		return sdl_fb_ops.setup(settings, res_setting, res_desc);
 	}
 
 	return -EINVAL;
@@ -248,8 +251,8 @@ int main(int argc, const char *argv[])
 	exit_if(r && print_setup_as_args(&setup) < 0,
 		"unable to print setup");
 
-	exit_if(!(rototiller.module = til_lookup_module(til_settings_get_key(setup.module, 0))),
-		"unable to lookup module from settings \"%s\"", til_settings_get_key(setup.module, 0));
+	exit_if(!(rototiller.module = til_lookup_module(til_settings_get_key(setup.module, 0, NULL))),
+		"unable to lookup module from settings \"%s\"", til_settings_get_key(setup.module, 0, NULL));
 
 	exit_if((r = til_fb_new(fb_ops, setup.video, NUM_FB_PAGES, &rototiller.fb)) < 0,
 		"unable to create fb: %s", strerror(-r));