From 20d37fb75197de5248528c5164f8cc86f7161b22 Mon Sep 17 00:00:00 2001
From: Artur Sinila <freesoftware@logarithmus.dev>
Date: Mon, 24 Jan 2022 20:19:09 +0200
Subject: [PATCH] Refactor RGB & XYZ colors into structs

---
 color_math.c | 49 +++++++++++++++++++++++++------------------------
 color_math.h | 10 +++++++++-
 main.c       | 14 ++++++--------
 3 files changed, 40 insertions(+), 33 deletions(-)

diff --git a/color_math.c b/color_math.c
index b850b96..ace8b17 100644
--- a/color_math.c
+++ b/color_math.c
@@ -159,31 +159,32 @@ static double clamp(double value) {
 	}
 }
 
-static void xyz_to_srgb(double x, double y, double z, double *r, double *g, double *b) {
+static struct rgb xyz_to_srgb(const struct xyz *xyz) {
 	// http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
-	*r = srgb_gamma(clamp(3.2404542 * x - 1.5371385 * y - 0.4985314 * z), 2.2);
-	*g = srgb_gamma(clamp(-0.9692660 * x + 1.8760108 * y + 0.0415560 * z), 2.2);
-	*b = srgb_gamma(clamp(0.0556434 * x - 0.2040259 * y + 1.0572252 * z), 2.2);
+	return (struct rgb) {
+		.r = srgb_gamma(clamp(3.2404542 * xyz->x - 1.5371385 * xyz->y - 0.4985314 * xyz->z), 2.2),
+		.g = srgb_gamma(clamp(-0.9692660 * xyz->x + 1.8760108 * xyz->y + 0.0415560 * xyz->z), 2.2),
+		.b = srgb_gamma(clamp(0.0556434 * xyz->x - 0.2040259 * xyz->y + 1.0572252 * xyz->z), 2.2)
+	};
 }
 
-static void srgb_normalize(double *r, double *g, double *b) {
-	double maxw = fmaxl(*r, fmaxl(*g, *b));
-	*r /= maxw;
-	*g /= maxw;
-	*b /= maxw;
+static void srgb_normalize(struct rgb *rgb) {
+	double maxw = fmax(rgb->r, fmax(rgb->g, rgb->b));
+	rgb->r /= maxw;
+	rgb->g /= maxw;
+	rgb->b /= maxw;
 }
 
-void calc_whitepoint(int temp, double *rw, double *gw, double *bw) {
+struct rgb calc_whitepoint(int temp) {
 	if (temp == 6500) {
-		*rw = *gw = *bw = 1.0;
-		return;
+		return (struct rgb) {.r = 1.0, .g = 1.0, .b = 1.0};
 	}
 
-	double x = 1.0, y = 1.0;
+	struct xyz wp;
 	if (temp >= 25000) {
-		illuminant_d(25000, &x, &y);
+		illuminant_d(25000, &wp.x, &wp.y);
 	} else if (temp >= 4000) {
-		illuminant_d(temp, &x, &y);
+		illuminant_d(temp, &wp.x, &wp.y);
 	} else if (temp >= 2500) {
 		double x1, y1, x2, y2;
 		illuminant_d(temp, &x1, &y1);
@@ -191,16 +192,16 @@ void calc_whitepoint(int temp, double *rw, double *gw, double *bw) {
 
 		double factor = (4000 - temp) / 1500;
 		double sinefactor = (cos(M_PI*factor) + 1.0) / 2.0;
-		x = x1 * sinefactor + x2 * (1.0 - sinefactor);
-		y = y1 * sinefactor + y2 * (1.0 - sinefactor);
-	} else if (temp >= 1667) {
-		planckian_locus(temp, &x, &y);
-	} else {
-		planckian_locus(1667, &x, &y);
+		wp.x = x1 * sinefactor + x2 * (1.0 - sinefactor);
+		wp.y = y1 * sinefactor + y2 * (1.0 - sinefactor);
+	} else  {
+		planckian_locus(temp >= 1667 ? temp : 1667, &wp.x, &wp.y);
 	}
-	double z = 1.0 - x - y;
+	wp.z = 1.0 - wp.x - wp.y;
 
-	xyz_to_srgb(x, y, z, rw, gw, bw);
-	srgb_normalize(rw, gw, bw);
+	struct rgb wp_rgb = xyz_to_srgb(&wp);
+	srgb_normalize(&wp_rgb);
+
+	return wp_rgb;
 }
 
diff --git a/color_math.h b/color_math.h
index 629d2b7..b49d119 100644
--- a/color_math.h
+++ b/color_math.h
@@ -22,7 +22,15 @@ struct sun {
 	time_t dusk;
 };
 
+struct rgb {
+  double r, g, b;
+};
+
+struct xyz {
+  double x, y, z;
+};
+
 enum sun_condition calc_sun(struct tm *tm, double latitude, struct sun *sun);
-void calc_whitepoint(int temp, double *rw, double *gw, double *bw);
+struct rgb calc_whitepoint(int temp);
 
 #endif
diff --git a/main.c b/main.c
index 6378a3c..a2937cd 100644
--- a/main.c
+++ b/main.c
@@ -573,21 +573,19 @@ static void fill_gamma_table(uint16_t *table, uint32_t ramp_size, double rw,
 	}
 }
 
-static void set_temperature(struct output *output, double rw,
-		double gw, double bw, double gamma) {
+static void set_temperature(struct output *output, const struct rgb *wp, double gamma) {
 	if (output->gamma_control == NULL || output->table_fd == -1) {
 		return;
 	}
-	fill_gamma_table(output->table, output->ramp_size, rw, gw, bw, gamma);
+	fill_gamma_table(output->table, output->ramp_size, wp->r, wp->g, wp->b, gamma);
 	lseek(output->table_fd, 0, SEEK_SET);
 	zwlr_gamma_control_v1_set_gamma(output->gamma_control,
 			output->table_fd);
 }
 
 static void set_temperature_all_outputs(struct wl_list *outputs,
-		struct config *cfg, int temp, double gamma) {
-	double rw, gw, bw;
-	calc_whitepoint(temp, &rw, &gw, &bw);
+		const struct config *cfg, int temp, double gamma) {
+	struct rgb wp = calc_whitepoint(temp);
 
 	// If outputs specified by user, then set temperature only for them.
 	// Otherwise set temperature for all outputs.
@@ -600,7 +598,7 @@ static void set_temperature_all_outputs(struct wl_list *outputs,
 					fprintf(stderr,
 						"setting temperature on '%s' to %d K\n",
 						output->name, temp);
-					set_temperature(output, rw, gw, bw, gamma);
+					set_temperature(output, &wp, gamma);
 					output_exists = true;
 					break;
 				}
@@ -616,7 +614,7 @@ static void set_temperature_all_outputs(struct wl_list *outputs,
 			fprintf(stderr,
 				"setting temperature on output '%d' to %d K\n",
 				output->id, temp);
-			set_temperature(output, rw, gw, bw, gamma);
+			set_temperature(output, &wp, gamma);
 		}
 	}
 }