Add feature to adjust fade duration (without Elektra)

src/options.c

@@ -193,6 +193,7 @@ print_help(const char *program_name)
 		" color effect\n"
 		"  -x\t\tReset mode (remove adjustment from screen)\n"
 		"  -r\t\tDisable fading between color temperatures\n"
+        "  -f\t\tSet fade duration (for fading between color temperatures) in full seconds\n"
 		"  -t DAY:NIGHT\tColor temperature to set at daytime/night\n"),
 	      stdout);
 	fputs("\n", stdout);
@@ -320,6 +321,7 @@ options_init(options_t *options)
 	options->provider_args = NULL;
 
 	options->use_fade = -1;
+    options->fade_duration = -1;
 	options->preserve_gamma = 1;
 	options->mode = PROGRAM_MODE_CONTINUAL;
 	options->verbose = 0;
@@ -456,6 +458,16 @@ parse_command_line_option(
 	case 'r':
 		options->use_fade = 0;
 		break;
+    case 'f':
+        errno = 0;
+        long fade_duration = strtol(value, NULL, 10);
+        if (errno != 0 || fade_duration <= 0) {
+            fputs(_("Malformed fade duration argument.\n"), stderr);
+            fputs(_("Try `-h' for more information.\n"), stderr);
+            return -1;
+        }
+        options->fade_duration = fade_duration;
+        break;
 	case 't':
 		s = strchr(value, ':');
 		if (s == NULL) {
@@ -495,7 +507,7 @@ options_parse_args(
 {
 	const char* program_name = argv[0];
 	int opt;
-	while ((opt = getopt(argc, argv, "b:c:g:hl:m:oO:pPrt:vVx")) != -1) {
+	while ((opt = getopt(argc, argv, "b:c:g:hl:m:oO:pPrf:t:vVx")) != -1) {
 		char option = opt;
 		int r = parse_command_line_option(
 			option, optarg, options, program_name, gamma_methods,
@@ -526,6 +538,16 @@ parse_config_file_option(
 		if (options->use_fade < 0) {
 			options->use_fade = !!atoi(value);
 		}
+	} else if (strcasecmp(key, "fade-duration") == 0) {
+	    if (options->fade_duration < 0) {
+            errno = 0;
+            long fade_duration = strtol(value, NULL, 10);
+            if (errno != 0 || fade_duration <= 0) {
+                fputs(_("Malformed fade duration setting.\n"), stderr);
+                return -1;
+            }
+            options->fade_duration = fade_duration;
+	    }
 	} else if (strcasecmp(key, "brightness") == 0) {
 		if (isnan(options->scheme.day.brightness)) {
 			options->scheme.day.brightness = atof(value);
@@ -676,4 +698,6 @@ options_set_defaults(options_t *options)
 	}
 
 	if (options->use_fade < 0) options->use_fade = 1;
+
+	if (options->fade_duration < 0) options->fade_duration = 4; // Set default fade duration to 4 seconds.
 }

src/options.h

@@ -34,6 +34,8 @@ typedef struct {
 	int temp_set;
 	/* Whether to fade between large skips in color temperature. */
 	int use_fade;
+	/* The length of the fade duration in seconds */
+	long fade_duration;
 	/* Whether to preserve gamma ramps if supported by gamma method. */
 	int preserve_gamma;
 

src/redshift.c

@@ -608,7 +608,8 @@ run_continual_mode(const location_provider_t *provider,
 		   const transition_scheme_t *scheme,
 		   const gamma_method_t *method,
 		   gamma_state_t *method_state,
-		   int use_fade, int preserve_gamma, int verbose)
+		   int use_fade, long fade_duration,
+		   int preserve_gamma, int verbose)
 {
 	int r;
 
@@ -761,8 +762,9 @@ run_continual_mode(const location_provider_t *provider,
 			     color_setting_diff_is_major(
 				     &target_interp,
 				     &prev_target_interp))) {
-				fade_length = FADE_LENGTH;
-				fade_time = 0;
+			    // Scale fade_length according to desired fade_duration.
+				fade_length = (FADE_LENGTH * (fade_duration * 1000)) / (FADE_LENGTH * SLEEP_DURATION_SHORT);
+                fade_time = 0;
 				fade_start_interp = interp;
 			}
 		}
@@ -1307,7 +1309,8 @@ main(int argc, char *argv[])
 		r = run_continual_mode(
 			options.provider, location_state, scheme,
 			options.method, method_state,
-			options.use_fade, options.preserve_gamma,
+			options.use_fade, options.fade_duration,
+			options.preserve_gamma,
 			options.verbose);
 		if (r < 0) exit(EXIT_FAILURE);
 	}