Fix HSL->RGB conversion

app/src/animation/color.c

@@ -5,8 +5,24 @@
  */
 
 #include <stdlib.h>
+
 #include <zmk/animation.h>
 
+static float fmod(float a, float b) {
+	float mod = a < 0 ? -a : a;
+	float x = b < 0 ? -b : b;
+
+	while (mod >= x) {
+		mod = mod - x;
+	}
+
+	return a < 0 ? -mod : mod;
+}
+
+static float fabs(float a) {
+	return a < 0 ? -a : a;
+}
+
 /**
  * HSL chosen over HSV/HSB as it shares the same parameters with LCh or HSLuv.
  * The latter color spaces could be interesting to experiment with because of their
@@ -16,39 +32,45 @@
  * Algorithm source: https://www.tlbx.app/color-converter
  */
 void zmk_hsl_to_rgb(const struct zmk_color_hsl *hsl, struct zmk_color_rgb *rgb) {
-	// float a = hsl->h / 60;
+	float s = (float) hsl->s / 100;
-	uint8_t a = hsl->h / 60;
+	float l = (float) hsl->l / 100;
-	float chroma = hsl->s * (1 - abs(2 * hsl->l - 1));
-	// I think 'a' actually needs to be a float here or this doesn't make sense.
-	// If uint, possible values are: (0,1), if float: (0...1)
-	float x = chroma * (1 - abs(a % 2 - 1));
-	float m = hsl->l - chroma / 2;
 
-	switch (a) {
+	float a = (float) hsl->h / 60;
+	float chroma = s * (1 - fabs(2 * l - 1));
+	float x = chroma * (1 - fabs(fmod(a, 2) - 1));
+	float m = l - chroma / 2;
+
+	switch ((uint8_t) a % 6) {
 	case 0:
 		rgb->r = m + chroma;
 		rgb->g = m + x;
 		rgb->b = m;
+		break;
 	case 1:
 		rgb->r = m + x;
 		rgb->g = m + chroma;
 		rgb->b = m;
+		break;
 	case 2:
 		rgb->r = m;
 		rgb->g = m + chroma;
 		rgb->b = m + x;
+		break;
 	case 3:
 		rgb->r = m;
 		rgb->g = m + x;
 		rgb->b = m + chroma;
+		break;
 	case 4:
 		rgb->r = m + x;
 		rgb->g = m;
 		rgb->b = m + chroma;
+		break;
 	case 5:
 		rgb->r = m + chroma;
 		rgb->g = m;
 		rgb->b = m + x;
+		break;
 	}
 }
 
@@ -56,9 +78,9 @@ void zmk_hsl_to_rgb(const struct zmk_color_hsl *hsl, struct zmk_color_rgb *rgb)
  * Converts ZMKs RGB (float) to Zephyr's led_rgb (uint8_t) format.
  */
 void zmk_rgb_to_led_rgb(const struct zmk_color_rgb *rgb, struct led_rgb *led) {
-	led->r = rgb->r * 255;
+	led->r = (uint8_t) (rgb->r * 255);
-	led->g = rgb->g * 255;
+	led->g = (uint8_t) (rgb->g * 255);
-	led->b = rgb->b * 255;
+	led->b = (uint8_t) (rgb->b * 255);
 }
 
 /**