args: move argument parsing/help output to libtil

This is totally opt-in for libtil callers, but is a step
towards enabling uniform cli invocations across frontends.

The help side of this is particularly janky, but since what's
appropriate there is directly related to the args parsing it
seems appropriate to bring along.  The janky part is the
implicit output formatting assumptions being made, as-is it
doesn't really lend itself well to being augmented into broader
frontend help output.  Alas, this is rototiller playground, so
let's just go easy and assume frontends will largely spit out
whatever this provides - or completely replace it if appropriate.

4 files changed, 73 insertions, 54 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index c0a20b5..6ca1d77 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,7 +1,7 @@
 SUBDIRS = libs modules
 
 noinst_LTLIBRARIES = libtil.la
-libtil_la_SOURCES = til_fb.c til_fb.h til_knobs.h til.c til.h til_settings.h til_settings.c til_threads.c til_threads.h til_util.c til_util.h
+libtil_la_SOURCES = til_args.c til_args.h til_fb.c til_fb.h til_knobs.h til.c til.h til_settings.h til_settings.c til_threads.c til_threads.h til_util.c til_util.h
 libtil_la_CPPFLAGS = -I@top_srcdir@/src
 libtil_la_LIBADD = modules/compose/libcompose.la modules/drizzle/libdrizzle.la modules/flui2d/libflui2d.la modules/julia/libjulia.la modules/meta2d/libmeta2d.la modules/montage/libmontage.la modules/pixbounce/libpixbounce.la modules/plasma/libplasma.la modules/plato/libplato.la modules/ray/libray.la modules/roto/libroto.la modules/rtv/librtv.la modules/snow/libsnow.la modules/sparkler/libsparkler.la modules/spiro/libspiro.la modules/stars/libstars.la modules/submit/libsubmit.la modules/swab/libswab.la modules/swarm/libswarm.la libs/grid/libgrid.la libs/puddle/libpuddle.la libs/ray/libray.la libs/sig/libsig.la libs/txt/libtxt.la libs/ascii/libascii.la libs/din/libdin.la
 
diff --git a/src/main.c b/src/main.c
index c028998..d07015b 100644
--- a/src/main.c
+++ b/src/main.c
@@ -11,6 +11,7 @@
 #include <unistd.h>
 
 #include "til.h"
+#include "til_args.h"
 #include "til_settings.h"
 #include "til_fb.h"
 #include "til_util.h"
@@ -44,48 +45,6 @@ typedef struct rototiller_t {
 static rototiller_t		rototiller;
 
 
-typedef struct argv_t {
-	const char	*module;
-	const char	*video;
-
-	unsigned	use_defaults:1;
-	unsigned	help:1;
-} argv_t;
-
-/*
- * ./rototiller --video=drm,dev=/dev/dri/card3,connector=VGA-1,mode=640x480@60
- * ./rototiller --video=sdl,size=640x480
- * ./rototiller --module=roto,foo=bar,module=settings
- * ./rototiller --defaults
- */
-static int parse_argv(int argc, const char *argv[], argv_t *res_args)
-{
-	int	i;
-
-	assert(argc > 0);
-	assert(argv);
-	assert(res_args);
-
-	/* this is intentionally being kept very simple, no new dependencies like getopt. */
-
-	for (i = 1; i < argc; i++) {
-		if (!strncmp("--video=", argv[i], 8)) {
-			res_args->video = &argv[i][8];
-		} else if (!strncmp("--module=", argv[i], 9)) {
-			res_args->module = &argv[i][9];
-		} else if (!strcmp("--defaults", argv[i])) {
-			res_args->use_defaults = 1;
-		} else if (!strcmp("--help", argv[i])) {
-			res_args->help = 1;
-		} else {
-			return -EINVAL;
-		}
-	}
-
-	return 0;
-}
-
-
 typedef struct setup_t {
 	til_settings_t	*module;
 	til_settings_t	*video;
@@ -148,7 +107,7 @@ static int setup_video(til_settings_t *settings, til_setting_desc_t **next_setti
 
 /* turn args into settings, automatically applying defaults if appropriate, or interactively if appropriate. */
 /* returns negative value on error, 0 when settings unchanged from args, 1 when changed */
-static int setup_from_args(argv_t *args, setup_t *res_setup)
+static int setup_from_args(til_args_t *args, setup_t *res_setup)
 {
 	int	r, changes = 0;
 	setup_t	setup;
@@ -232,15 +191,11 @@ _out:
 
 static int print_help(void)
 {
-	return printf(
-		"Run without any flags or partial settings for interactive mode.\n"
+	printf("Run without any flags or partial settings for interactive mode.\n"
 		"\n"
-		"Supported flags:\n"
-		"  --defaults	use defaults for unspecified settings\n"
-		"  --help	this help\n"
-		"  --module=	module settings\n"
-		"  --video=	video settings\n"
-		);
+		"Supported flags:\n");
+
+	return til_args_help(stdout);
 }
 
 
@@ -282,10 +237,10 @@ static void * rototiller_thread(void *_rt)
 int main(int argc, const char *argv[])
 {
 	setup_t		setup = {};
-	argv_t		args = {};
+	til_args_t	args = {};
 	int		r;
 
-	exit_if(parse_argv(argc, argv, &args) < 0,
+	exit_if(til_args_parse(argc, argv, &args) < 0,
 		"unable to process arguments");
 
 	if (args.help)
diff --git a/src/til_args.c b/src/til_args.c
new file mode 100644
index 0000000..ae1346c
--- /dev/null
+++ b/src/til_args.c
@@ -0,0 +1,47 @@
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+
+#include "til_args.h"
+
+/*
+ * ./rototiller --video=drm,dev=/dev/dri/card3,connector=VGA-1,mode=640x480@60
+ * ./rototiller --video=sdl,size=640x480
+ * ./rototiller --module=roto,foo=bar,module=settings
+ * ./rototiller --defaults
+ */
+int til_args_parse(int argc, const char *argv[], til_args_t *res_args)
+{
+	assert(argc > 0);
+	assert(argv);
+	assert(res_args);
+
+	/* this is intentionally being kept very simple, no new dependencies like getopt. */
+
+	for (int i = 1; i < argc; i++) {
+		if (!strncmp("--video=", argv[i], 8)) {
+			res_args->video = &argv[i][8];
+		} else if (!strncmp("--module=", argv[i], 9)) {
+			res_args->module = &argv[i][9];
+		} else if (!strcmp("--defaults", argv[i])) {
+			res_args->use_defaults = 1;
+		} else if (!strcmp("--help", argv[i])) {
+			res_args->help = 1;
+		} else {
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+
+int til_args_help(FILE *out)
+{
+	return fprintf(out,
+		"  --defaults	use defaults for unspecified settings\n"
+		"  --help	this help\n"
+		"  --module=	module settings\n"
+		"  --video=	video settings\n"
+		);
+}
diff --git a/src/til_args.h b/src/til_args.h
new file mode 100644
index 0000000..018ae80
--- /dev/null
+++ b/src/til_args.h
@@ -0,0 +1,17 @@
+#ifndef _TIL_ARGS_H
+#define _TIL_ARGS_H
+
+#include <stdio.h>
+
+typedef struct til_args_t {
+	const char	*module;
+	const char	*video;
+
+	unsigned	use_defaults:1;
+	unsigned	help:1;
+} til_args_t;
+
+int til_args_parse(int argc, const char *argv[], til_args_t *res_args);
+int til_args_help(FILE *out);
+
+#endif