Move options handling to separate file

Create options.c which contains functions for initializing and
parsing options from the command line and the configuration file.
Program options that were previously local variables in main() are
moved to the options_t struct.

6 files changed, 870 insertions, 716 deletions

diff --git a/po/POTFILES.in b/po/POTFILES.in
index e6b9c4d..5ef8dac 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -5,7 +5,7 @@ data/applications/redshift.desktop.in
 data/applications/redshift-gtk.desktop.in
 
 src/redshift.c
-
+src/options.c
 src/config-ini.c
 
 src/gamma-drm.c
diff --git a/src/Makefile.am b/src/Makefile.am
index 99c8a2e..8aa96ea 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -14,6 +14,7 @@ redshift_SOURCES = \
 	gamma-dummy.c gamma-dummy.h \
 	hooks.c hooks.h \
 	location-manual.c location-manual.h \
+	options.c options.h \
 	pipeutils.c pipeutils.h \
 	redshift.c redshift.h \
 	signals.c signals.h \
diff --git a/src/options.c b/src/options.c
new file mode 100644
index 0000000..8a0a0d2
--- /dev/null
+++ b/src/options.c
@@ -0,0 +1,672 @@
+/* options.c -- Program options
+   This file is part of Redshift.
+
+   Redshift is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   Redshift is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with Redshift.  If not, see <http://www.gnu.org/licenses/>.
+
+   Copyright (c) 2017  Jon Lund Steffensen <jonlst@gmail.com>
+*/
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <math.h>
+
+#ifdef ENABLE_NLS
+# include <libintl.h>
+# define _(s) gettext(s)
+#else
+# define _(s) s
+#endif
+
+#include "redshift.h"
+#include "config-ini.h"
+#include "options.h"
+#include "solar.h"
+
+/* Angular elevation of the sun at which the color temperature
+   transition period starts and ends (in degress).
+   Transition during twilight, and while the sun is lower than
+   3.0 degrees above the horizon. */
+#define TRANSITION_LOW     SOLAR_CIVIL_TWILIGHT_ELEV
+#define TRANSITION_HIGH    3.0
+
+/* Default values for parameters. */
+#define DEFAULT_DAY_TEMP    6500
+#define DEFAULT_NIGHT_TEMP  4500
+#define DEFAULT_BRIGHTNESS   1.0
+#define DEFAULT_GAMMA        1.0
+
+
+/* A brightness string contains either one floating point value,
+   or two values separated by a colon. */
+static void
+parse_brightness_string(
+	const char *str, float *bright_day, float *bright_night)
+{
+	char *s = strchr(str, ':');
+	if (s == NULL) {
+		/* Same value for day and night. */
+		*bright_day = *bright_night = atof(str);
+	} else {
+		*(s++) = '\0';
+		*bright_day = atof(str);
+		*bright_night = atof(s);
+	}
+}
+
+/* A gamma string contains either one floating point value,
+   or three values separated by colon. */
+static int
+parse_gamma_string(const char *str, float gamma[])
+{
+	char *s = strchr(str, ':');
+	if (s == NULL) {
+		/* Use value for all channels */
+		float g = atof(str);
+		gamma[0] = gamma[1] = gamma[2] = g;
+	} else {
+		/* Parse separate value for each channel */
+		*(s++) = '\0';
+		char *g_s = s;
+		s = strchr(s, ':');
+		if (s == NULL) return -1;
+
+		*(s++) = '\0';
+		gamma[0] = atof(str); /* Red */
+		gamma[1] = atof(g_s); /* Blue */
+		gamma[2] = atof(s); /* Green */
+	}
+
+	return 0;
+}
+
+/* Parse transition time string e.g. "04:50". Returns negative on failure,
+   otherwise the parsed time is returned as seconds since midnight. */
+static int
+parse_transition_time(const char *str, const char **end)
+{
+	const char *min = NULL;
+	errno = 0;
+	long hours = strtol(str, (char **)&min, 10);
+	if (errno != 0 || min == str || min[0] != ':' ||
+	    hours < 0 || hours >= 24) {
+		return -1;
+	}
+
+	min += 1;
+	errno = 0;
+	long minutes = strtol(min, (char **)end, 10);
+	if (errno != 0 || *end == min || minutes < 0 || minutes >= 60) {
+		return -1;
+	}
+
+	return minutes * 60 + hours * 3600;
+}
+
+/* Parse transition range string e.g. "04:50-6:20". Returns negative on
+   failure, otherwise zero. Parsed start and end times are returned as seconds
+   since midnight. */
+static int
+parse_transition_range(const char *str, time_range_t *range)
+{
+	const char *next = NULL;
+	int start_time = parse_transition_time(str, &next);
+	if (start_time < 0) return -1;
+
+	int end_time;
+	if (next[0] == '\0') {
+		end_time = start_time;
+	} else if (next[0] == '-') {
+		next += 1;
+		const char *end = NULL;
+		end_time = parse_transition_time(next, &end);
+		if (end_time < 0 || end[0] != '\0') return -1;
+	} else {
+		return -1;
+	}
+
+	range->start = start_time;
+	range->end = end_time;
+
+	return 0;
+}
+
+/* Print help text. */
+static void
+print_help(const char *program_name)
+{
+	/* TRANSLATORS: help output 1
+	   LAT is latitude, LON is longitude,
+	   DAY is temperature at daytime,
+	   NIGHT is temperature at night
+	   no-wrap */
+	printf(_("Usage: %s -l LAT:LON -t DAY:NIGHT [OPTIONS...]\n"),
+		program_name);
+	fputs("\n", stdout);
+
+	/* TRANSLATORS: help output 2
+	   no-wrap */
+	fputs(_("Set color temperature of display"
+		" according to time of day.\n"), stdout);
+	fputs("\n", stdout);
+
+	/* TRANSLATORS: help output 3
+	   no-wrap */
+	fputs(_("  -h\t\tDisplay this help message\n"
+		"  -v\t\tVerbose output\n"
+		"  -V\t\tShow program version\n"), stdout);
+	fputs("\n", stdout);
+
+	/* TRANSLATORS: help output 4
+	   `list' must not be translated
+	   no-wrap */
+	fputs(_("  -b DAY:NIGHT\tScreen brightness to apply (between 0.1 and 1.0)\n"
+		"  -c FILE\tLoad settings from specified configuration file\n"
+		"  -g R:G:B\tAdditional gamma correction to apply\n"
+		"  -l LAT:LON\tYour current location\n"
+		"  -l PROVIDER\tSelect provider for automatic"
+		" location updates\n"
+		"  \t\t(Type `list' to see available providers)\n"
+		"  -m METHOD\tMethod to use to set color temperature\n"
+		"  \t\t(Type `list' to see available methods)\n"
+		"  -o\t\tOne shot mode (do not continuously adjust"
+		" color temperature)\n"
+		"  -O TEMP\tOne shot manual mode (set color temperature)\n"
+		"  -p\t\tPrint mode (only print parameters and exit)\n"
+		"  -x\t\tReset mode (remove adjustment from screen)\n"
+		"  -r\t\tDisable fading between color temperatures\n"
+		"  -t DAY:NIGHT\tColor temperature to set at daytime/night\n"),
+	      stdout);
+	fputs("\n", stdout);
+
+	/* TRANSLATORS: help output 5 */
+	printf(_("The neutral temperature is %uK. Using this value will not change "
+		 "the color\ntemperature of the display. Setting the color temperature "
+		 "to a value higher\nthan this results in more blue light, and setting "
+		 "a lower value will result in\nmore red light.\n"),
+		 NEUTRAL_TEMP);
+
+	fputs("\n", stdout);
+
+	/* TRANSLATORS: help output 6 */
+	printf(_("Default values:\n\n"
+		 "  Daytime temperature: %uK\n"
+		 "  Night temperature: %uK\n"),
+	       DEFAULT_DAY_TEMP, DEFAULT_NIGHT_TEMP);
+
+	fputs("\n", stdout);
+
+	/* TRANSLATORS: help output 7 */
+	printf(_("Please report bugs to <%s>\n"), PACKAGE_BUGREPORT);
+}
+
+/* Print list of adjustment methods. */
+static void
+print_method_list(const gamma_method_t *gamma_methods)
+{
+	fputs(_("Available adjustment methods:\n"), stdout);
+	for (int i = 0; gamma_methods[i].name != NULL; i++) {
+		printf("  %s\n", gamma_methods[i].name);
+	}
+
+	fputs("\n", stdout);
+	fputs(_("Specify colon-separated options with"
+		" `-m METHOD:OPTIONS'.\n"), stdout);
+	/* TRANSLATORS: `help' must not be translated. */
+	fputs(_("Try `-m METHOD:help' for help.\n"), stdout);
+}
+
+/* Print list of location providers. */
+static void
+print_provider_list(const location_provider_t location_providers[])
+{
+	fputs(_("Available location providers:\n"), stdout);
+	for (int i = 0; location_providers[i].name != NULL; i++) {
+		printf("  %s\n", location_providers[i].name);
+	}
+
+	fputs("\n", stdout);
+	fputs(_("Specify colon-separated options with"
+		"`-l PROVIDER:OPTIONS'.\n"), stdout);
+	/* TRANSLATORS: `help' must not be translated. */
+	fputs(_("Try `-l PROVIDER:help' for help.\n"), stdout);
+}
+
+/* Return the gamma method with the given name. */
+static const gamma_method_t *
+find_gamma_method(const gamma_method_t gamma_methods[], const char *name)
+{
+	const gamma_method_t *method = NULL;
+	for (int i = 0; gamma_methods[i].name != NULL; i++) {
+		const gamma_method_t *m = &gamma_methods[i];
+		if (strcasecmp(name, m->name) == 0) {
+			method = m;
+			break;
+		}
+	}
+
+	return method;
+}
+
+/* Return location provider with the given name. */
+static const location_provider_t *
+find_location_provider(
+	const location_provider_t location_providers[], const char *name)
+{
+	const location_provider_t *provider = NULL;
+	for (int i = 0; location_providers[i].name != NULL; i++) {
+		const location_provider_t *p = &location_providers[i];
+		if (strcasecmp(name, p->name) == 0) {
+			provider = p;
+			break;
+		}
+	}
+
+	return provider;
+}
+
+
+/* Initialize options struct. */
+void
+options_init(options_t *options)
+{
+	options->config_filepath = NULL;
+
+	/* Default elevation values. */
+	options->scheme.high = TRANSITION_HIGH;
+	options->scheme.low = TRANSITION_LOW;
+
+	/* Settings for day, night and transition period.
+	   Initialized to indicate that the values are not set yet. */
+	options->scheme.use_time = 0;
+	options->scheme.dawn.start = -1;
+	options->scheme.dawn.end = -1;
+	options->scheme.dusk.start = -1;
+	options->scheme.dusk.end = -1;
+
+	options->scheme.day.temperature = -1;
+	options->scheme.day.gamma[0] = NAN;
+	options->scheme.day.brightness = NAN;
+
+	options->scheme.night.temperature = -1;
+	options->scheme.night.gamma[0] = NAN;
+	options->scheme.night.brightness = NAN;
+
+	/* Temperature for manual mode */
+	options->temp_set = -1;
+
+	options->method = NULL;
+	options->method_args = NULL;
+
+	options->provider = NULL;
+	options->provider_args = NULL;
+
+	options->use_fade = -1;
+	options->mode = PROGRAM_MODE_CONTINUAL;
+	options->verbose = 0;
+}
+
+/* Parse command line arguments. */
+void
+options_parse_args(
+	options_t *options, int argc, char *argv[],
+	const gamma_method_t *gamma_methods,
+	const location_provider_t *location_providers)
+{
+	int r;
+	char *s;
+
+	/* Parse command line arguments. */
+	int opt;
+	while ((opt = getopt(argc, argv, "b:c:g:hl:m:oO:prt:vVx")) != -1) {
+		switch (opt) {
+		case 'b':
+			parse_brightness_string(
+				optarg,
+				&options->scheme.day.brightness,
+				&options->scheme.night.brightness);
+			break;
+		case 'c':
+			free(options->config_filepath);
+			options->config_filepath = strdup(optarg);
+			break;
+		case 'g':
+			r = parse_gamma_string(
+				optarg, options->scheme.day.gamma);
+			if (r < 0) {
+				fputs(_("Malformed gamma argument.\n"),
+				      stderr);
+				fputs(_("Try `-h' for more"
+					" information.\n"), stderr);
+				exit(EXIT_FAILURE);
+			}
+
+			/* Set night gamma to the same value as day gamma.
+			   To set these to distinct values use the config
+			   file. */
+			memcpy(options->scheme.night.gamma,
+			       options->scheme.day.gamma,
+			       sizeof(options->scheme.night.gamma));
+			break;
+		case 'h':
+			print_help(argv[0]);
+			exit(EXIT_SUCCESS);
+			break;
+		case 'l':
+			/* Print list of providers if argument is `list' */
+			if (strcasecmp(optarg, "list") == 0) {
+				print_provider_list(location_providers);
+				exit(EXIT_SUCCESS);
+			}
+
+			char *provider_name = NULL;
+
+			/* Don't save the result of strtof(); we simply want
+			   to know if optarg can be parsed as a float. */
+			errno = 0;
+			char *end;
+			strtof(optarg, &end);
+			if (errno == 0 && *end == ':') {
+				/* Use instead as arguments to `manual'. */
+				provider_name = "manual";
+				options->provider_args = optarg;
+			} else {
+				/* Split off provider arguments. */
+				s = strchr(optarg, ':');
+				if (s != NULL) {
+					*(s++) = '\0';
+					options->provider_args = s;
+				}
+
+				provider_name = optarg;
+			}
+
+			/* Lookup provider from name. */
+			options->provider = find_location_provider(
+				location_providers, provider_name);
+			if (options->provider == NULL) {
+				fprintf(stderr, _("Unknown location provider"
+						  " `%s'.\n"), provider_name);
+				exit(EXIT_FAILURE);
+			}
+
+			/* Print provider help if arg is `help'. */
+			if (options->provider_args != NULL &&
+			    strcasecmp(options->provider_args, "help") == 0) {
+				options->provider->print_help(stdout);
+				exit(EXIT_SUCCESS);
+			}
+			break;
+		case 'm':
+			/* Print list of methods if argument is `list' */
+			if (strcasecmp(optarg, "list") == 0) {
+				print_method_list(gamma_methods);
+				exit(EXIT_SUCCESS);
+			}
+
+			/* Split off method arguments. */
+			s = strchr(optarg, ':');
+			if (s != NULL) {
+				*(s++) = '\0';
+				options->method_args = s;
+			}
+
+			/* Find adjustment method by name. */
+			options->method = find_gamma_method(
+				gamma_methods, optarg);
+			if (options->method == NULL) {
+				/* TRANSLATORS: This refers to the method
+				   used to adjust colors e.g VidMode */
+				fprintf(stderr, _("Unknown adjustment method"
+						  " `%s'.\n"), optarg);
+				exit(EXIT_FAILURE);
+			}
+
+			/* Print method help if arg is `help'. */
+			if (options->method_args != NULL &&
+			    strcasecmp(options->method_args, "help") == 0) {
+				options->method->print_help(stdout);
+				exit(EXIT_SUCCESS);
+			}
+			break;
+		case 'o':
+			options->mode = PROGRAM_MODE_ONE_SHOT;
+			break;
+		case 'O':
+			options->mode = PROGRAM_MODE_MANUAL;
+			options->temp_set = atoi(optarg);
+			break;
+		case 'p':
+			options->mode = PROGRAM_MODE_PRINT;
+			break;
+		case 'r':
+			options->use_fade = 0;
+			break;
+		case 't':
+			s = strchr(optarg, ':');
+			if (s == NULL) {
+				fputs(_("Malformed temperature argument.\n"),
+				      stderr);
+				fputs(_("Try `-h' for more information.\n"),
+				      stderr);
+				exit(EXIT_FAILURE);
+			}
+			*(s++) = '\0';
+			options->scheme.day.temperature = atoi(optarg);
+			options->scheme.night.temperature = atoi(s);
+			break;
+		case 'v':
+			options->verbose = 1;
+			break;
+		case 'V':
+			printf("%s\n", PACKAGE_STRING);
+			exit(EXIT_SUCCESS);
+			break;
+		case 'x':
+			options->mode = PROGRAM_MODE_RESET;
+			break;
+		case '?':
+			fputs(_("Try `-h' for more information.\n"), stderr);
+			exit(EXIT_FAILURE);
+			break;
+		}
+	}
+}
+
+/* Parse options defined in the config file. */
+void
+options_parse_config_file(
+	options_t *options, config_ini_state_t *config_state,
+	const gamma_method_t *gamma_methods,
+	const location_provider_t *location_providers)
+{
+	int r;
+
+	/* Read global config settings. */
+	config_ini_section_t *section = config_ini_get_section(
+		config_state, "redshift");
+	if (section == NULL) return;
+
+	config_ini_setting_t *setting = section->settings;
+	while (setting != NULL) {
+		if (strcasecmp(setting->name, "temp-day") == 0) {
+			if (options->scheme.day.temperature < 0) {
+				options->scheme.day.temperature =
+					atoi(setting->value);
+			}
+		} else if (strcasecmp(setting->name, "temp-night") == 0) {
+			if (options->scheme.night.temperature < 0) {
+				options->scheme.night.temperature =
+					atoi(setting->value);
+			}
+		} else if (strcasecmp(setting->name, "transition") == 0 ||
+			   strcasecmp(setting->name, "fade") == 0) {
+			/* "fade" is preferred, "transition" is
+			   deprecated as the setting key. */
+			if (options->use_fade < 0) {
+				options->use_fade = !!atoi(setting->value);
+			}
+		} else if (strcasecmp(setting->name, "brightness") == 0) {
+			if (isnan(options->scheme.day.brightness)) {
+				options->scheme.day.brightness =
+					atof(setting->value);
+			}
+			if (isnan(options->scheme.night.brightness)) {
+				options->scheme.night.brightness =
+					atof(setting->value);
+			}
+		} else if (strcasecmp(setting->name, "brightness-day") == 0) {
+			if (isnan(options->scheme.day.brightness)) {
+				options->scheme.day.brightness =
+					atof(setting->value);
+			}
+		} else if (strcasecmp(setting->name,
+			              "brightness-night") == 0) {
+			if (isnan(options->scheme.night.brightness)) {
+				options->scheme.night.brightness =
+					atof(setting->value);
+			}
+		} else if (strcasecmp(setting->name, "elevation-high") == 0) {
+			options->scheme.high = atof(setting->value);
+		} else if (strcasecmp(setting->name, "elevation-low") == 0) {
+			options->scheme.low = atof(setting->value);
+		} else if (strcasecmp(setting->name, "gamma") == 0) {
+			if (isnan(options->scheme.day.gamma[0])) {
+				r = parse_gamma_string(
+					setting->value,
+					options->scheme.day.gamma);
+				if (r < 0) {
+					fputs(_("Malformed gamma setting.\n"),
+					      stderr);
+					exit(EXIT_FAILURE);
+				}
+				memcpy(options->scheme.night.gamma,
+				       options->scheme.day.gamma,
+				       sizeof(options->scheme.night.gamma));
+			}
+		} else if (strcasecmp(setting->name, "gamma-day") == 0) {
+			if (isnan(options->scheme.day.gamma[0])) {
+				r = parse_gamma_string(
+					setting->value,
+					options->scheme.day.gamma);
+				if (r < 0) {
+					fputs(_("Malformed gamma setting.\n"),
+					      stderr);
+					exit(EXIT_FAILURE);
+				}
+			}
+		} else if (strcasecmp(setting->name, "gamma-night") == 0) {
+			if (isnan(options->scheme.night.gamma[0])) {
+				r = parse_gamma_string(
+					setting->value,
+					options->scheme.night.gamma);
+				if (r < 0) {
+					fputs(_("Malformed gamma setting.\n"),
+					      stderr);
+					exit(EXIT_FAILURE);
+				}
+			}
+		} else if (strcasecmp(setting->name,
+				      "adjustment-method") == 0) {
+			if (options->method == NULL) {
+				options->method = find_gamma_method(
+					gamma_methods, setting->value);
+				if (options->method == NULL) {
+					fprintf(stderr, _("Unknown adjustment"
+							  " method `%s'.\n"),
+						setting->value);
+					exit(EXIT_FAILURE);
+				}
+			}
+		} else if (strcasecmp(setting->name,
+				      "location-provider") == 0) {
+			if (options->provider == NULL) {
+				options->provider = find_location_provider(
+					location_providers,
+					setting->value);
+				if (options->provider == NULL) {
+					fprintf(stderr, _("Unknown location"
+							  " provider `%s'.\n"),
+						setting->value);
+					exit(EXIT_FAILURE);
+				}
+			}
+		} else if (strcasecmp(setting->name, "dawn-time") == 0) {
+			if (options->scheme.dawn.start < 0) {
+				int r = parse_transition_range(
+					setting->value, &options->scheme.dawn);
+				if (r < 0) {
+					fprintf(stderr, _("Malformed dawn-time"
+							  " setting `%s'.\n"),
+						setting->value);
+					exit(EXIT_FAILURE);
+				}
+			}
+		} else if (strcasecmp(setting->name, "dusk-time") == 0) {
+			if (options->scheme.dusk.start < 0) {
+				int r = parse_transition_range(
+					setting->value, &options->scheme.dusk);
+				if (r < 0) {
+					fprintf(stderr, _("Malformed dusk-time"
+							  " setting `%s'.\n"),
+						setting->value);
+					exit(EXIT_FAILURE);
+				}
+			}
+		} else {
+			fprintf(stderr, _("Unknown configuration"
+					  " setting `%s'.\n"),
+				setting->name);
+		}
+
+		setting = setting->next;
+	}
+}
+
+/* Replace unspecified options with default values. */
+void
+options_set_defaults(options_t *options)
+{
+	if (options->scheme.day.temperature < 0) {
+		options->scheme.day.temperature = DEFAULT_DAY_TEMP;
+	}
+	if (options->scheme.night.temperature < 0) {
+		options->scheme.night.temperature = DEFAULT_NIGHT_TEMP;
+	}
+
+	if (isnan(options->scheme.day.brightness)) {
+		options->scheme.day.brightness = DEFAULT_BRIGHTNESS;
+	}
+	if (isnan(options->scheme.night.brightness)) {
+		options->scheme.night.brightness = DEFAULT_BRIGHTNESS;
+	}
+
+	if (isnan(options->scheme.day.gamma[0])) {
+		options->scheme.day.gamma[0] = DEFAULT_GAMMA;
+		options->scheme.day.gamma[1] = DEFAULT_GAMMA;
+		options->scheme.day.gamma[2] = DEFAULT_GAMMA;
+	}
+	if (isnan(options->scheme.night.gamma[0])) {
+		options->scheme.night.gamma[0] = DEFAULT_GAMMA;
+		options->scheme.night.gamma[1] = DEFAULT_GAMMA;
+		options->scheme.night.gamma[2] = DEFAULT_GAMMA;
+	}
+
+	if (options->use_fade < 0) options->use_fade = 1;
+}
diff --git a/src/options.h b/src/options.h
new file mode 100644
index 0000000..95a31b1
--- /dev/null
+++ b/src/options.h
@@ -0,0 +1,61 @@
+/* options.h -- Program options header
+   This file is part of Redshift.
+
+   Redshift is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   Redshift is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with Redshift.  If not, see <http://www.gnu.org/licenses/>.
+
+   Copyright (c) 2017  Jon Lund Steffensen <jonlst@gmail.com>
+*/
+
+#ifndef REDSHIFT_OPTIONS_H
+#define REDSHIFT_OPTIONS_H
+
+#include "redshift.h"
+
+typedef struct {
+	/* Path to config file */
+	char *config_filepath;
+
+	transition_scheme_t scheme;
+	program_mode_t mode;
+	int verbose;
+
+	/* Temperature to set in manual mode. */
+	int temp_set;
+	/* Whether to fade between large skips in color temperature. */
+	int use_fade;
+
+	/* Selected gamma method. */
+	const gamma_method_t *method;
+	/* Arguments for gamma method. */
+	char *method_args;
+
+	/* Selected location provider. */
+	const location_provider_t *provider;
+	/* Arguments for location provider. */
+	char *provider_args;
+} options_t;
+
+
+void options_init(options_t *options);
+void options_parse_args(
+	options_t *options, int argc, char *argv[],
+	const gamma_method_t *gamma_methods,
+	const location_provider_t *location_providers);
+void options_parse_config_file(
+	options_t *options, config_ini_state_t *config_state,
+	const gamma_method_t *gamma_methods,
+	const location_provider_t *location_providers);
+void options_set_defaults(options_t *options);
+
+#endif /* ! REDSHIFT_OPTIONS_H */
diff --git a/src/redshift.c b/src/redshift.c
index 6e63b2c..1b31647 100644
--- a/src/redshift.c
+++ b/src/redshift.c
@@ -64,6 +64,7 @@ int poll(struct pollfd *fds, int nfds, int timeout) { abort(); return -1; }
 #include "systemtime.h"
 #include "hooks.h"
 #include "signals.h"
+#include "options.h"
 
 /* pause() is not defined on windows platform but is not needed either.
    Use a noop macro instead. */
@@ -120,22 +121,6 @@ int poll(struct pollfd *fds, int nfds, int timeout) { abort(); return -1; }
 #define MIN_GAMMA   0.1
 #define MAX_GAMMA  10.0
 
-/* Default values for parameters. */
-#define DEFAULT_DAY_TEMP    6500
-#define DEFAULT_NIGHT_TEMP  4500
-#define DEFAULT_BRIGHTNESS   1.0
-#define DEFAULT_GAMMA        1.0
-
-/* The color temperature when no adjustment is applied. */
-#define NEUTRAL_TEMP  6500
-
-/* Angular elevation of the sun at which the color temperature
-   transition period starts and ends (in degress).
-   Transition during twilight, and while the sun is lower than
-   3.0 degrees above the horizon. */
-#define TRANSITION_LOW     SOLAR_CIVIL_TWILIGHT_ELEV
-#define TRANSITION_HIGH    3.0
-
 /* Duration of sleep between screen updates (milliseconds). */
 #define SLEEP_DURATION        5000
 #define SLEEP_DURATION_SHORT  100
@@ -143,34 +128,6 @@ int poll(struct pollfd *fds, int nfds, int timeout) { abort(); return -1; }
 /* Length of fade in numbers of short sleep durations. */
 #define FADE_LENGTH  40
 
-/* Program modes. */
-typedef enum {
-	PROGRAM_MODE_CONTINUAL,
-	PROGRAM_MODE_ONE_SHOT,
-	PROGRAM_MODE_PRINT,
-	PROGRAM_MODE_RESET,
-	PROGRAM_MODE_MANUAL
-} program_mode_t;
-
-/* Time range.
-   Fields are offsets from midnight in seconds. */
-typedef struct {
-	int start;
-	int end;
-} time_range_t;
-
-/* Transition scheme.
-   The solar elevations at which the transition begins/ends,
-   and the association color settings. */
-typedef struct {
-	double high;
-	double low;
-	int use_time; /* When enabled, ignore elevation and use time ranges. */
-	time_range_t dawn;
-	time_range_t dusk;
-	color_setting_t day;
-	color_setting_t night;
-} transition_scheme_t;
 
 /* Names of periods of day */
 static const char *period_names[] = {
@@ -345,105 +302,6 @@ color_setting_diff_is_major(
 }
 
 
-static void
-print_help(const char *program_name)
-{
-	/* TRANSLATORS: help output 1
-	   LAT is latitude, LON is longitude,
-	   DAY is temperature at daytime,
-	   NIGHT is temperature at night
-	   no-wrap */
-	printf(_("Usage: %s -l LAT:LON -t DAY:NIGHT [OPTIONS...]\n"),
-		program_name);
-	fputs("\n", stdout);
-
-	/* TRANSLATORS: help output 2
-	   no-wrap */
-	fputs(_("Set color temperature of display"
-		" according to time of day.\n"), stdout);
-	fputs("\n", stdout);
-
-	/* TRANSLATORS: help output 3
-	   no-wrap */
-	fputs(_("  -h\t\tDisplay this help message\n"
-		"  -v\t\tVerbose output\n"
-		"  -V\t\tShow program version\n"), stdout);
-	fputs("\n", stdout);
-
-	/* TRANSLATORS: help output 4
-	   `list' must not be translated
-	   no-wrap */
-	fputs(_("  -b DAY:NIGHT\tScreen brightness to apply (between 0.1 and 1.0)\n"
-		"  -c FILE\tLoad settings from specified configuration file\n"
-		"  -g R:G:B\tAdditional gamma correction to apply\n"
-		"  -l LAT:LON\tYour current location\n"
-		"  -l PROVIDER\tSelect provider for automatic"
-		" location updates\n"
-		"  \t\t(Type `list' to see available providers)\n"
-		"  -m METHOD\tMethod to use to set color temperature\n"
-		"  \t\t(Type `list' to see available methods)\n"
-		"  -o\t\tOne shot mode (do not continuously adjust"
-		" color temperature)\n"
-		"  -O TEMP\tOne shot manual mode (set color temperature)\n"
-		"  -p\t\tPrint mode (only print parameters and exit)\n"
-		"  -x\t\tReset mode (remove adjustment from screen)\n"
-		"  -r\t\tDisable fading between color temperatures\n"
-		"  -t DAY:NIGHT\tColor temperature to set at daytime/night\n"),
-	      stdout);
-	fputs("\n", stdout);
-
-	/* TRANSLATORS: help output 5 */
-	printf(_("The neutral temperature is %uK. Using this value will not change "
-		 "the color\ntemperature of the display. Setting the color temperature "
-		 "to a value higher\nthan this results in more blue light, and setting "
-		 "a lower value will result in\nmore red light.\n"),
-		 NEUTRAL_TEMP);
-
-	fputs("\n", stdout);
-
-	/* TRANSLATORS: help output 6 */
-	printf(_("Default values:\n\n"
-		 "  Daytime temperature: %uK\n"
-		 "  Night temperature: %uK\n"),
-	       DEFAULT_DAY_TEMP, DEFAULT_NIGHT_TEMP);
-
-	fputs("\n", stdout);
-
-	/* TRANSLATORS: help output 7 */
-	printf(_("Please report bugs to <%s>\n"), PACKAGE_BUGREPORT);
-}
-
-static void
-print_method_list(const gamma_method_t *gamma_methods)
-{
-	fputs(_("Available adjustment methods:\n"), stdout);
-	for (int i = 0; gamma_methods[i].name != NULL; i++) {
-		printf("  %s\n", gamma_methods[i].name);
-	}
-
-	fputs("\n", stdout);
-	fputs(_("Specify colon-separated options with"
-		" `-m METHOD:OPTIONS'.\n"), stdout);
-	/* TRANSLATORS: `help' must not be translated. */
-	fputs(_("Try `-m METHOD:help' for help.\n"), stdout);
-}
-
-static void
-print_provider_list(const location_provider_t location_providers[])
-{
-	fputs(_("Available location providers:\n"), stdout);
-	for (int i = 0; location_providers[i].name != NULL; i++) {
-		printf("  %s\n", location_providers[i].name);
-	}
-
-	fputs("\n", stdout);
-	fputs(_("Specify colon-separated options with"
-		"`-l PROVIDER:OPTIONS'.\n"), stdout);
-	/* TRANSLATORS: `help' must not be translated. */
-	fputs(_("Try `-l PROVIDER:help' for help.\n"), stdout);
-}
-
-
 static int
 provider_try_start(const location_provider_t *provider,
 		   location_state_t **state, config_ini_state_t *config,
@@ -614,98 +472,6 @@ method_try_start(const gamma_method_t *method,
 	return 0;
 }
 
-/* A gamma string contains either one floating point value,
-   or three values separated by colon. */
-static int
-parse_gamma_string(const char *str, float gamma[])
-{
-	char *s = strchr(str, ':');
-	if (s == NULL) {
-		/* Use value for all channels */
-		float g = atof(str);
-		gamma[0] = gamma[1] = gamma[2] = g;
-	} else {
-		/* Parse separate value for each channel */
-		*(s++) = '\0';
-		char *g_s = s;
-		s = strchr(s, ':');
-		if (s == NULL) return -1;
-
-		*(s++) = '\0';
-		gamma[0] = atof(str); /* Red */
-		gamma[1] = atof(g_s); /* Blue */
-		gamma[2] = atof(s); /* Green */
-	}
-
-	return 0;
-}
-
-/* A brightness string contains either one floating point value,
-   or two values separated by a colon. */
-static void
-parse_brightness_string(const char *str, float *bright_day, float *bright_night)
-{
-	char *s = strchr(str, ':');
-	if (s == NULL) {
-		/* Same value for day and night. */
-		*bright_day = *bright_night = atof(str);
-	} else {
-		*(s++) = '\0';
-		*bright_day = atof(str);
-		*bright_night = atof(s);
-	}
-}
-
-/* Parse transition time string e.g. "04:50". Returns negative on failure,
-   otherwise the parsed time is returned as seconds since midnight. */
-static int
-parse_transition_time(const char *str, const char **end)
-{
-	const char *min = NULL;
-	errno = 0;
-	long hours = strtol(str, (char **)&min, 10);
-	if (errno != 0 || min == str || min[0] != ':' ||
-	    hours < 0 || hours >= 24) {
-		return -1;
-	}
-
-	min += 1;
-	errno = 0;
-	long minutes = strtol(min, (char **)end, 10);
-	if (errno != 0 || *end == min || minutes < 0 || minutes >= 60) {
-		return -1;
-	}
-
-	return minutes * 60 + hours * 3600;
-}
-
-/* Parse transition range string e.g. "04:50-6:20". Returns negative on
-   failure, otherwise zero. Parsed start and end times are returned as seconds
-   since midnight. */
-static int
-parse_transition_range(const char *str, time_range_t *range)
-{
-	const char *next = NULL;
-	int start_time = parse_transition_time(str, &next);
-	if (start_time < 0) return -1;
-
-	int end_time;
-	if (next[0] == '\0') {
-		end_time = start_time;
-	} else if (next[0] == '-') {
-		next += 1;
-		const char *end = NULL;
-		end_time = parse_transition_time(next, &end);
-		if (end_time < 0 || end[0] != '\0') return -1;
-	} else {
-		return -1;
-	}
-
-	range->start = start_time;
-	range->end = end_time;
-
-	return 0;
-}
 
 /* Check whether gamma is within allowed levels. */
 static int
@@ -746,37 +512,6 @@ location_is_valid(const location_t *location)
 	return 1;
 }
 
-static const gamma_method_t *
-find_gamma_method(const gamma_method_t gamma_methods[], const char *name)
-{
-	const gamma_method_t *method = NULL;
-	for (int i = 0; gamma_methods[i].name != NULL; i++) {
-		const gamma_method_t *m = &gamma_methods[i];
-		if (strcasecmp(name, m->name) == 0) {
-			method = m;
-			break;
-		}
-	}
-
-	return method;
-}
-
-static const location_provider_t *
-find_location_provider(
-	const location_provider_t location_providers[], const char *name)
-{
-	const location_provider_t *provider = NULL;
-	for (int i = 0; location_providers[i].name != NULL; i++) {
-		const location_provider_t *p = &location_providers[i];
-		if (strcasecmp(name, p->name) == 0) {
-			provider = p;
-			break;
-		}
-	}
-
-	return provider;
-}
-
 /* Wait for location to become available from provider.
    Waits until timeout (milliseconds) has elapsed or forever if timeout
    is -1. Writes location to loc. Returns -1 on error,
@@ -1156,31 +891,6 @@ main(int argc, char *argv[])
 	textdomain(PACKAGE);
 #endif
 
-	/* Initialize settings to NULL values. */
-	char *config_filepath = NULL;
-
-	/* Settings for day, night and transition period.
-	   Initialized to indicate that the values are not set yet. */
-	transition_scheme_t scheme =
-		{ TRANSITION_HIGH, TRANSITION_LOW };
-
-	scheme.use_time = 0;
-	scheme.dawn.start = -1;
-	scheme.dawn.end = -1;
-	scheme.dusk.start = -1;
-	scheme.dusk.end = -1;
-
-	scheme.day.temperature = -1;
-	scheme.day.gamma[0] = NAN;
-	scheme.day.brightness = NAN;
-
-	scheme.night.temperature = -1;
-	scheme.night.gamma[0] = NAN;
-	scheme.night.brightness = NAN;
-
-	/* Temperature for manual mode */
-	int temp_set = -1;
-
 	/* List of gamma methods. */
 	const gamma_method_t gamma_methods[] = {
 #ifdef ENABLE_DRM
@@ -1202,9 +912,6 @@ main(int argc, char *argv[])
 		{ NULL }
 	};
 
-	const gamma_method_t *method = NULL;
-	char *method_args = NULL;
-
 	/* List of location providers. */
 	const location_provider_t location_providers[] = {
 #ifdef ENABLE_GEOCLUE2
@@ -1217,383 +924,52 @@ main(int argc, char *argv[])
 		{ NULL }
 	};
 
-	const location_provider_t *provider = NULL;
-	char *provider_args = NULL;
-
-	int use_fade = -1;
-	program_mode_t mode = PROGRAM_MODE_CONTINUAL;
-	int verbose = 0;
-	char *s;
-
 	/* Flush messages consistently even if redirected to a pipe or
 	   file.  Change the flush behaviour to line-buffered, without
 	   changing the actual buffers being used. */
 	setvbuf(stdout, NULL, _IOLBF, 0);
 	setvbuf(stderr, NULL, _IOLBF, 0);
 
-	/* Parse command line arguments. */
-	int opt;
-	while ((opt = getopt(argc, argv, "b:c:g:hl:m:oO:prt:vVx")) != -1) {
-		switch (opt) {
-		case 'b':
-			parse_brightness_string(optarg,
-						&scheme.day.brightness,
-						&scheme.night.brightness);
-			break;
-		case 'c':
-			free(config_filepath);
-			config_filepath = strdup(optarg);
-			break;
-		case 'g':
-			r = parse_gamma_string(optarg, scheme.day.gamma);
-			if (r < 0) {
-				fputs(_("Malformed gamma argument.\n"),
-				      stderr);
-				fputs(_("Try `-h' for more"
-					" information.\n"), stderr);
-				exit(EXIT_FAILURE);
-			}
-
-			/* Set night gamma to the same value as day gamma.
-			   To set these to distinct values use the config
-			   file. */
-			memcpy(scheme.night.gamma, scheme.day.gamma,
-			       sizeof(scheme.night.gamma));
-			break;
-		case 'h':
-			print_help(argv[0]);
-			exit(EXIT_SUCCESS);
-			break;
-		case 'l':
-			/* Print list of providers if argument is `list' */
-			if (strcasecmp(optarg, "list") == 0) {
-				print_provider_list(location_providers);
-				exit(EXIT_SUCCESS);
-			}
-
-			char *provider_name = NULL;
-
-			/* Don't save the result of strtof(); we simply want
-			   to know if optarg can be parsed as a float. */
-			errno = 0;
-			char *end;
-			strtof(optarg, &end);
-			if (errno == 0 && *end == ':') {
-				/* Use instead as arguments to `manual'. */
-				provider_name = "manual";
-				provider_args = optarg;
-			} else {
-				/* Split off provider arguments. */
-				s = strchr(optarg, ':');
-				if (s != NULL) {
-					*(s++) = '\0';
-					provider_args = s;
-				}
-
-				provider_name = optarg;
-			}
-
-			/* Lookup provider from name. */
-			provider = find_location_provider(
-				location_providers, provider_name);
-			if (provider == NULL) {
-				fprintf(stderr, _("Unknown location provider"
-						  " `%s'.\n"), provider_name);
-				exit(EXIT_FAILURE);
-			}
-
-			/* Print provider help if arg is `help'. */
-			if (provider_args != NULL &&
-			    strcasecmp(provider_args, "help") == 0) {
-				provider->print_help(stdout);
-				exit(EXIT_SUCCESS);
-			}
-			break;
-		case 'm':
-			/* Print list of methods if argument is `list' */
-			if (strcasecmp(optarg, "list") == 0) {
-				print_method_list(gamma_methods);
-				exit(EXIT_SUCCESS);
-			}
-
-			/* Split off method arguments. */
-			s = strchr(optarg, ':');
-			if (s != NULL) {
-				*(s++) = '\0';
-				method_args = s;
-			}
-
-			/* Find adjustment method by name. */
-			method = find_gamma_method(gamma_methods, optarg);
-			if (method == NULL) {
-				/* TRANSLATORS: This refers to the method
-				   used to adjust colors e.g VidMode */
-				fprintf(stderr, _("Unknown adjustment method"
-						  " `%s'.\n"), optarg);
-				exit(EXIT_FAILURE);
-			}
-
-			/* Print method help if arg is `help'. */
-			if (method_args != NULL &&
-			    strcasecmp(method_args, "help") == 0) {
-				method->print_help(stdout);
-				exit(EXIT_SUCCESS);
-			}
-			break;
-		case 'o':
-			mode = PROGRAM_MODE_ONE_SHOT;
-			break;
-		case 'O':
-			mode = PROGRAM_MODE_MANUAL;
-			temp_set = atoi(optarg);
-			break;
-		case 'p':
-			mode = PROGRAM_MODE_PRINT;
-			break;
-		case 'r':
-			use_fade = 0;
-			break;
-		case 't':
-			s = strchr(optarg, ':');
-			if (s == NULL) {
-				fputs(_("Malformed temperature argument.\n"),
-				      stderr);
-				fputs(_("Try `-h' for more information.\n"),
-				      stderr);
-				exit(EXIT_FAILURE);
-			}
-			*(s++) = '\0';
-			scheme.day.temperature = atoi(optarg);
-			scheme.night.temperature = atoi(s);
-			break;
-		case 'v':
-			verbose = 1;
-			break;
-                case 'V':
-                        printf("%s\n", PACKAGE_STRING);
-                        exit(EXIT_SUCCESS);
-                        break;
-		case 'x':
-			mode = PROGRAM_MODE_RESET;
-			break;
-		case '?':
-			fputs(_("Try `-h' for more information.\n"), stderr);
-			exit(EXIT_FAILURE);
-			break;
-		}
-	}
+	options_t options;
+	options_init(&options);
+	options_parse_args(
+		&options, argc, argv, gamma_methods, location_providers);
 
 	/* Load settings from config file. */
 	config_ini_state_t config_state;
-	r = config_ini_init(&config_state, config_filepath);
+	r = config_ini_init(&config_state, options.config_filepath);
 	if (r < 0) {
 		fputs("Unable to load config file.\n", stderr);
 		exit(EXIT_FAILURE);
 	}
 
-	free(config_filepath);
+	free(options.config_filepath);
 
-	/* Read global config settings. */
-	config_ini_section_t *section = config_ini_get_section(&config_state,
-							       "redshift");
-	if (section != NULL) {
-		config_ini_setting_t *setting = section->settings;
-		while (setting != NULL) {
-			if (strcasecmp(setting->name, "temp-day") == 0) {
-				if (scheme.day.temperature < 0) {
-					scheme.day.temperature =
-						atoi(setting->value);
-				}
-			} else if (strcasecmp(setting->name,
-					      "temp-night") == 0) {
-				if (scheme.night.temperature < 0) {
-					scheme.night.temperature =
-						atoi(setting->value);
-				}
-			} else if (strcasecmp(
-					setting->name, "transition") == 0 ||
-				   strcasecmp(setting->name, "fade") == 0) {
-				/* "fade" is preferred, "transition" is
-				   deprecated as the setting key. */
-				if (use_fade < 0) {
-					use_fade = !!atoi(setting->value);
-				}
-			} else if (strcasecmp(setting->name,
-					      "brightness") == 0) {
-				if (isnan(scheme.day.brightness)) {
-					scheme.day.brightness =
-						atof(setting->value);
-				}
-				if (isnan(scheme.night.brightness)) {
-					scheme.night.brightness =
-						atof(setting->value);
-				}
-			} else if (strcasecmp(setting->name,
-					      "brightness-day") == 0) {
-				if (isnan(scheme.day.brightness)) {
-					scheme.day.brightness =
-						atof(setting->value);
-				}
-			} else if (strcasecmp(setting->name,
-					      "brightness-night") == 0) {
-				if (isnan(scheme.night.brightness)) {
-					scheme.night.brightness =
-						atof(setting->value);
-				}
-			} else if (strcasecmp(setting->name,
-					      "elevation-high") == 0) {
-				scheme.high = atof(setting->value);
-			} else if (strcasecmp(setting->name,
-					      "elevation-low") == 0) {
-				scheme.low = atof(setting->value);
-			} else if (strcasecmp(setting->name, "gamma") == 0) {
-				if (isnan(scheme.day.gamma[0])) {
-					r = parse_gamma_string(setting->value,
-							       scheme.day.gamma);
-					if (r < 0) {
-						fputs(_("Malformed gamma"
-							" setting.\n"),
-						      stderr);
-						exit(EXIT_FAILURE);
-					}
-					memcpy(scheme.night.gamma, scheme.day.gamma,
-					       sizeof(scheme.night.gamma));
-				}
-			} else if (strcasecmp(setting->name, "gamma-day") == 0) {
-				if (isnan(scheme.day.gamma[0])) {
-					r = parse_gamma_string(setting->value,
-							       scheme.day.gamma);
-					if (r < 0) {
-						fputs(_("Malformed gamma"
-							" setting.\n"),
-						      stderr);
-						exit(EXIT_FAILURE);
-					}
-				}
-			} else if (strcasecmp(setting->name, "gamma-night") == 0) {
-				if (isnan(scheme.night.gamma[0])) {
-					r = parse_gamma_string(setting->value,
-							       scheme.night.gamma);
-					if (r < 0) {
-						fputs(_("Malformed gamma"
-							" setting.\n"),
-						      stderr);
-						exit(EXIT_FAILURE);
-					}
-				}
-			} else if (strcasecmp(setting->name,
-					      "adjustment-method") == 0) {
-				if (method == NULL) {
-					method = find_gamma_method(
-						gamma_methods, setting->value);
-					if (method == NULL) {
-						fprintf(stderr, _("Unknown"
-								  " adjustment"
-								  " method"
-								  " `%s'.\n"),
-							setting->value);
-						exit(EXIT_FAILURE);
-					}
-				}
-			} else if (strcasecmp(setting->name,
-					      "location-provider") == 0) {
-				if (provider == NULL) {
-					provider = find_location_provider(
-						location_providers,
-						setting->value);
-					if (provider == NULL) {
-						fprintf(stderr, _("Unknown"
-								  " location"
-								  " provider"
-								  " `%s'.\n"),
-							setting->value);
-						exit(EXIT_FAILURE);
-					}
-				}
-			} else if (strcasecmp(setting->name,
-					      "dawn-time") == 0) {
-				if (scheme.dawn.start < 0) {
-					int r = parse_transition_range(
-						setting->value, &scheme.dawn);
-					if (r < 0) {
-						fprintf(stderr, _("Malformed"
-								  " dawn-time"
-								  " setting"
-								  " `%s'.\n"),
-							setting->value);
-						exit(EXIT_FAILURE);
-					}
-				}
-			} else if (strcasecmp(setting->name,
-					      "dusk-time") == 0) {
-				if (scheme.dusk.start < 0) {
-					int r = parse_transition_range(
-						setting->value, &scheme.dusk);
-					if (r < 0) {
-						fprintf(stderr, _("Malformed"
-								  " dusk-time"
-								  " setting"
-								  " `%s'.\n"),
-							setting->value);
-						exit(EXIT_FAILURE);
-					}
-				}
-			} else {
-				fprintf(stderr, _("Unknown configuration"
-						  " setting `%s'.\n"),
-					setting->name);
-			}
-			setting = setting->next;
-		}
-	}
-
-	/* Use default values for settings that were neither defined in
-	   the config file nor on the command line. */
-	if (scheme.day.temperature < 0) {
-		scheme.day.temperature = DEFAULT_DAY_TEMP;
-	}
-	if (scheme.night.temperature < 0) {
-		scheme.night.temperature = DEFAULT_NIGHT_TEMP;
-	}
+	options_parse_config_file(
+		&options, &config_state, gamma_methods, location_providers);
 
-	if (isnan(scheme.day.brightness)) {
-		scheme.day.brightness = DEFAULT_BRIGHTNESS;
-	}
-	if (isnan(scheme.night.brightness)) {
-		scheme.night.brightness = DEFAULT_BRIGHTNESS;
-	}
+	options_set_defaults(&options);
 
-	if (isnan(scheme.day.gamma[0])) {
-		scheme.day.gamma[0] = DEFAULT_GAMMA;
-		scheme.day.gamma[1] = DEFAULT_GAMMA;
-		scheme.day.gamma[2] = DEFAULT_GAMMA;
-	}
-	if (isnan(scheme.night.gamma[0])) {
-		scheme.night.gamma[0] = DEFAULT_GAMMA;
-		scheme.night.gamma[1] = DEFAULT_GAMMA;
-		scheme.night.gamma[2] = DEFAULT_GAMMA;
-	}
-
-	if (use_fade < 0) use_fade = 1;
-
-	if (scheme.dawn.start >= 0 || scheme.dawn.end >= 0 ||
-	    scheme.dusk.start >= 0 || scheme.dusk.end >= 0) {
-		if (scheme.dawn.start < 0 || scheme.dawn.end < 0 ||
-		    scheme.dusk.start < 0 || scheme.dusk.end < 0) {
+	if (options.scheme.dawn.start >= 0 || options.scheme.dawn.end >= 0 ||
+	    options.scheme.dusk.start >= 0 || options.scheme.dusk.end >= 0) {
+		if (options.scheme.dawn.start < 0 ||
+		    options.scheme.dawn.end < 0 ||
+		    options.scheme.dusk.start < 0 ||
+		    options.scheme.dusk.end < 0) {
 			fputs(_("Partitial time-configuration not"
 				" supported!\n"), stderr);
 			exit(EXIT_FAILURE);
 		}
 
-		if (scheme.dawn.start > scheme.dawn.end ||
-		    scheme.dawn.end > scheme.dusk.start ||
-		    scheme.dusk.start > scheme.dusk.end) {
+		if (options.scheme.dawn.start > options.scheme.dawn.end ||
+		    options.scheme.dawn.end > options.scheme.dusk.start ||
+		    options.scheme.dusk.start > options.scheme.dusk.end) {
 			fputs(_("Invalid dawn/dusk time configuration!\n"),
 			      stderr);
 			exit(EXIT_FAILURE);
 		}
 
-		scheme.use_time = 1;
+		options.scheme.use_time = 1;
 	}
 
 	/* Initialize location provider if needed. If provider is NULL
@@ -1602,14 +978,15 @@ main(int argc, char *argv[])
 
 	/* Location is not needed for reset mode and manual mode. */
 	int need_location =
-		mode != PROGRAM_MODE_RESET &&
-		mode != PROGRAM_MODE_MANUAL &&
-		!scheme.use_time;
+		options.mode != PROGRAM_MODE_RESET &&
+		options.mode != PROGRAM_MODE_MANUAL &&
+		!options.scheme.use_time;
 	if (need_location) {
-		if (provider != NULL) {
+		if (options.provider != NULL) {
 			/* Use provider specified on command line. */
-			r = provider_try_start(provider, &location_state,
-					       &config_state, provider_args);
+			r = provider_try_start(
+				options.provider, &location_state,
+				&config_state, options.provider_args);
 			if (r < 0) exit(EXIT_FAILURE);
 		} else {
 			/* Try all providers, use the first that works. */
@@ -1630,13 +1007,13 @@ main(int argc, char *argv[])
 
 				/* Found provider that works. */
 				printf(_("Using provider `%s'.\n"), p->name);
-				provider = p;
+				options.provider = p;
 				break;
 			}
 
 			/* Failure if no providers were successful at this
 			   point. */
-			if (provider == NULL) {
+			if (options.provider == NULL) {
 				fputs(_("No more location providers"
 					" to try.\n"), stderr);
 				exit(EXIT_FAILURE);
@@ -1644,33 +1021,33 @@ main(int argc, char *argv[])
 		}
 
 		/* Solar elevations */
-		if (scheme.high < scheme.low) {
+		if (options.scheme.high < options.scheme.low) {
 			fprintf(stderr,
 				_("High transition elevation cannot be lower than"
 				  " the low transition elevation.\n"));
 			exit(EXIT_FAILURE);
 		}
 
-		if (verbose) {
+		if (options.verbose) {
 			/* TRANSLATORS: Append degree symbols if possible. */
 			printf(_("Solar elevations: day above %.1f, night below %.1f\n"),
-			       scheme.high, scheme.low);
+			       options.scheme.high, options.scheme.low);
 		}
 	}
 
-	if (mode != PROGRAM_MODE_RESET &&
-	    mode != PROGRAM_MODE_MANUAL) {
-		if (verbose) {
+	if (options.mode != PROGRAM_MODE_RESET &&
+	    options.mode != PROGRAM_MODE_MANUAL) {
+		if (options.verbose) {
 			printf(_("Temperatures: %dK at day, %dK at night\n"),
-			       scheme.day.temperature,
-			       scheme.night.temperature);
+			       options.scheme.day.temperature,
+			       options.scheme.night.temperature);
 		}
 
 		/* Color temperature */
-		if (scheme.day.temperature < MIN_TEMP ||
-		    scheme.day.temperature > MAX_TEMP ||
-		    scheme.night.temperature < MIN_TEMP ||
-		    scheme.night.temperature > MAX_TEMP) {
+		if (options.scheme.day.temperature < MIN_TEMP ||
+		    options.scheme.day.temperature > MAX_TEMP ||
+		    options.scheme.night.temperature < MIN_TEMP ||
+		    options.scheme.night.temperature > MAX_TEMP) {
 			fprintf(stderr,
 				_("Temperature must be between %uK and %uK.\n"),
 				MIN_TEMP, MAX_TEMP);
@@ -1678,9 +1055,10 @@ main(int argc, char *argv[])
 		}
 	}
 
-	if (mode == PROGRAM_MODE_MANUAL) {
+	if (options.mode == PROGRAM_MODE_MANUAL) {
 		/* Check color temperature to be set */
-		if (temp_set < MIN_TEMP || temp_set > MAX_TEMP) {
+		if (options.temp_set < MIN_TEMP ||
+		    options.temp_set > MAX_TEMP) {
 			fprintf(stderr,
 				_("Temperature must be between %uK and %uK.\n"),
 				MIN_TEMP, MAX_TEMP);
@@ -1689,52 +1067,57 @@ main(int argc, char *argv[])
 	}
 
 	/* Brightness */
-	if (scheme.day.brightness < MIN_BRIGHTNESS ||
-	    scheme.day.brightness > MAX_BRIGHTNESS ||
-	    scheme.night.brightness < MIN_BRIGHTNESS ||
-	    scheme.night.brightness > MAX_BRIGHTNESS) {
+	if (options.scheme.day.brightness < MIN_BRIGHTNESS ||
+	    options.scheme.day.brightness > MAX_BRIGHTNESS ||
+	    options.scheme.night.brightness < MIN_BRIGHTNESS ||
+	    options.scheme.night.brightness > MAX_BRIGHTNESS) {
 		fprintf(stderr,
 			_("Brightness values must be between %.1f and %.1f.\n"),
 			MIN_BRIGHTNESS, MAX_BRIGHTNESS);
 		exit(EXIT_FAILURE);
 	}
 
-	if (verbose) {
+	if (options.verbose) {
 		printf(_("Brightness: %.2f:%.2f\n"),
-		       scheme.day.brightness, scheme.night.brightness);
+		       options.scheme.day.brightness,
+		       options.scheme.night.brightness);
 	}
 
 	/* Gamma */
-	if (!gamma_is_valid(scheme.day.gamma) ||
-	    !gamma_is_valid(scheme.night.gamma)) {
+	if (!gamma_is_valid(options.scheme.day.gamma) ||
+	    !gamma_is_valid(options.scheme.night.gamma)) {
 		fprintf(stderr,
 			_("Gamma value must be between %.1f and %.1f.\n"),
 			MIN_GAMMA, MAX_GAMMA);
 		exit(EXIT_FAILURE);
 	}
 
-	if (verbose) {
+	if (options.verbose) {
 		/* TRANSLATORS: The string in parenthesis is either
 		   Daytime or Night (translated). */
 		printf(_("Gamma (%s): %.3f, %.3f, %.3f\n"),
-		       _("Daytime"), scheme.day.gamma[0],
-		       scheme.day.gamma[1], scheme.day.gamma[2]);
+		       _("Daytime"), options.scheme.day.gamma[0],
+		       options.scheme.day.gamma[1],
+		       options.scheme.day.gamma[2]);
 		printf(_("Gamma (%s): %.3f, %.3f, %.3f\n"),
-		       _("Night"), scheme.night.gamma[0],
-		       scheme.night.gamma[1], scheme.night.gamma[2]);
+		       _("Night"), options.scheme.night.gamma[0],
+		       options.scheme.night.gamma[1],
+		       options.scheme.night.gamma[2]);
 	}
 
+	transition_scheme_t *scheme = &options.scheme;
+
 	/* Initialize gamma adjustment method. If method is NULL
 	   try all methods until one that works is found. */
 	gamma_state_t *method_state;
 
 	/* Gamma adjustment not needed for print mode */
-	if (mode != PROGRAM_MODE_PRINT) {
-		if (method != NULL) {
+	if (options.mode != PROGRAM_MODE_PRINT) {
+		if (options.method != NULL) {
 			/* Use method specified on command line. */
 			r = method_try_start(
-				method, &method_state, &config_state,
-				method_args);
+				options.method, &method_state, &config_state,
+				options.method_args);
 			if (r < 0) exit(EXIT_FAILURE);
 		} else {
 			/* Try all methods, use the first that works. */
@@ -1751,12 +1134,12 @@ main(int argc, char *argv[])
 
 				/* Found method that works. */
 				printf(_("Using method `%s'.\n"), m->name);
-				method = m;
+				options.method = m;
 				break;
 			}
 
 			/* Failure if no methods were successful at this point. */
-			if (method == NULL) {
+			if (options.method == NULL) {
 				fputs(_("No more methods to try.\n"), stderr);
 				exit(EXIT_FAILURE);
 			}
@@ -1765,7 +1148,7 @@ main(int argc, char *argv[])
 
 	config_ini_free(&config_state);
 
-	switch (mode) {
+	switch (options.mode) {
 	case PROGRAM_MODE_ONE_SHOT:
 	case PROGRAM_MODE_PRINT:
 	{
@@ -1776,7 +1159,7 @@ main(int argc, char *argv[])
 
 			/* Wait for location provider. */
 			int r = provider_get_location(
-				provider, location_state, -1, &loc);
+				options.provider, location_state, -1, &loc);
 			if (r < 0) {
 				fputs(_("Unable to get location"
 					" from provider.\n"), stderr);
@@ -1794,39 +1177,39 @@ main(int argc, char *argv[])
 		r = systemtime_get_time(&now);
 		if (r < 0) {
 			fputs(_("Unable to read system time.\n"), stderr);
-			method->free(method_state);
+			options.method->free(method_state);
 			exit(EXIT_FAILURE);
 		}
 
 		period_t period;
 		double transition_prog;
-		if (scheme.use_time) {
+		if (options.scheme.use_time) {
 			int time_offset = get_seconds_since_midnight(now);
-			period = get_period_from_time(&scheme, time_offset);
+			period = get_period_from_time(scheme, time_offset);
 			transition_prog = get_transition_progress_from_time(
-				&scheme, time_offset);
+				scheme, time_offset);
 		} else {
 			/* Current angular elevation of the sun */
 			double elevation = solar_elevation(
 				now, loc.lat, loc.lon);
-			if (verbose) {
+			if (options.verbose) {
 				/* TRANSLATORS: Append degree symbol if
 				   possible. */
 				printf(_("Solar elevation: %f\n"), elevation);
 			}
 
-			period = get_period_from_elevation(&scheme, elevation);
+			period = get_period_from_elevation(scheme, elevation);
 			transition_prog =
 				get_transition_progress_from_elevation(
-					&scheme, elevation);
+					scheme, elevation);
 		}
 
 		/* Use transition progress to set color temperature */
 		color_setting_t interp;
 		interpolate_transition_scheme(
-			&scheme, transition_prog, &interp);
+			scheme, transition_prog, &interp);
 
-		if (verbose || mode == PROGRAM_MODE_PRINT) {
+		if (options.verbose || options.mode == PROGRAM_MODE_PRINT) {
 			print_period(period, transition_prog);
 			printf(_("Color temperature: %uK\n"),
 			       interp.temperature);
@@ -1834,13 +1217,14 @@ main(int argc, char *argv[])
 			       interp.brightness);
 		}
 
-		if (mode != PROGRAM_MODE_PRINT) {
+		if (options.mode != PROGRAM_MODE_PRINT) {
 			/* Adjust temperature */
-			r = method->set_temperature(method_state, &interp);
+			r = options.method->set_temperature(
+				method_state, &interp);
 			if (r < 0) {
 				fputs(_("Temperature adjustment failed.\n"),
 				      stderr);
-				method->free(method_state);
+				options.method->free(method_state);
 				exit(EXIT_FAILURE);
 			}
 
@@ -1848,7 +1232,7 @@ main(int argc, char *argv[])
 			   automatically revert when the process exits.
 			   Therefore, we have to loop until CTRL-C is received.
 			   */
-			if (strcmp(method->name, "quartz") == 0) {
+			if (strcmp(options.method->name, "quartz") == 0) {
 				fputs(_("Press ctrl-c to stop...\n"), stderr);
 				pause();
 			}
@@ -1857,22 +1241,25 @@ main(int argc, char *argv[])
 	break;
 	case PROGRAM_MODE_MANUAL:
 	{
-		if (verbose) printf(_("Color temperature: %uK\n"), temp_set);
+		if (options.verbose) {
+			printf(_("Color temperature: %uK\n"),
+			       options.temp_set);
+		}
 
 		/* Adjust temperature */
-		color_setting_t manual = scheme.day;
-		manual.temperature = temp_set;
-		r = method->set_temperature(method_state, &manual);
+		color_setting_t manual = scheme->day;
+		manual.temperature = options.temp_set;
+		r = options.method->set_temperature(method_state, &manual);
 		if (r < 0) {
 			fputs(_("Temperature adjustment failed.\n"), stderr);
-			method->free(method_state);
+			options.method->free(method_state);
 			exit(EXIT_FAILURE);
 		}
 
 		/* In Quartz (OSX) the gamma adjustments will automatically
 		   revert when the process exits. Therefore, we have to loop
 		   until CTRL-C is received. */
-		if (strcmp(method->name, "quartz") == 0) {
+		if (strcmp(options.method->name, "quartz") == 0) {
 			fputs(_("Press ctrl-c to stop...\n"), stderr);
 			pause();
 		}
@@ -1882,17 +1269,17 @@ main(int argc, char *argv[])
 	{
 		/* Reset screen */
 		color_setting_t reset = { NEUTRAL_TEMP, { 1.0, 1.0, 1.0 }, 1.0 };
-		r = method->set_temperature(method_state, &reset);
+		r = options.method->set_temperature(method_state, &reset);
 		if (r < 0) {
 			fputs(_("Temperature adjustment failed.\n"), stderr);
-			method->free(method_state);
+			options.method->free(method_state);
 			exit(EXIT_FAILURE);
 		}
 
 		/* In Quartz (OSX) the gamma adjustments will automatically
 		   revert when the process exits. Therefore, we have to loop
 		   until CTRL-C is received. */
-		if (strcmp(method->name, "quartz") == 0) {
+		if (strcmp(options.method->name, "quartz") == 0) {
 			fputs(_("Press ctrl-c to stop...\n"), stderr);
 			pause();
 		}
@@ -1900,22 +1287,23 @@ main(int argc, char *argv[])
 	break;
 	case PROGRAM_MODE_CONTINUAL:
 	{
-		r = run_continual_mode(provider, location_state, &scheme,
-				       method, method_state,
-				       use_fade, verbose);
+		r = run_continual_mode(
+			options.provider, location_state, scheme,
+			options.method, method_state,
+			options.use_fade, options.verbose);
 		if (r < 0) exit(EXIT_FAILURE);
 	}
 	break;
 	}
 
 	/* Clean up gamma adjustment state */
-	if (mode != PROGRAM_MODE_PRINT) {
-		method->free(method_state);
+	if (options.mode != PROGRAM_MODE_PRINT) {
+		options.method->free(method_state);
 	}
 
 	/* Clean up location provider state */
 	if (need_location) {
-		provider->free(location_state);
+		options.provider->free(location_state);
 	}
 
 	return EXIT_SUCCESS;
diff --git a/src/redshift.h b/src/redshift.h
index 98f9f37..f597c67 100644
--- a/src/redshift.h
+++ b/src/redshift.h
@@ -23,6 +23,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+/* The color temperature when no adjustment is applied. */
+#define NEUTRAL_TEMP  6500
+
 
 /* Location */
 typedef struct {
@@ -45,6 +48,35 @@ typedef struct {
 	float brightness;
 } color_setting_t;
 
+/* Program modes. */
+typedef enum {
+	PROGRAM_MODE_CONTINUAL,
+	PROGRAM_MODE_ONE_SHOT,
+	PROGRAM_MODE_PRINT,
+	PROGRAM_MODE_RESET,
+	PROGRAM_MODE_MANUAL
+} program_mode_t;
+
+/* Time range.
+   Fields are offsets from midnight in seconds. */
+typedef struct {
+	int start;
+	int end;
+} time_range_t;
+
+/* Transition scheme.
+   The solar elevations at which the transition begins/ends,
+   and the association color settings. */
+typedef struct {
+	double high;
+	double low;
+	int use_time; /* When enabled, ignore elevation and use time ranges. */
+	time_range_t dawn;
+	time_range_t dusk;
+	color_setting_t day;
+	color_setting_t night;
+} transition_scheme_t;
+
 
 /* Gamma adjustment method */
 typedef struct gamma_state gamma_state_t;