From 45c6a7f7e2e776878d5dd6da9296c5d6026942c2 Mon Sep 17 00:00:00 2001
From: David Phillips <david@yeah.nah.nz>
Date: Sun, 3 Mar 2019 14:58:41 +1300
Subject: Allow brightness set

---
 clock-disp.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 78 insertions(+), 2 deletions(-)

diff --git a/clock-disp.c b/clock-disp.c
index c8d8c74..8aa4fc3 100644
--- a/clock-disp.c
+++ b/clock-disp.c
@@ -12,6 +12,13 @@ enum ALIGN_MODE {
 	ALIGN_MODE_RIGHT,
 };
 
+//#define DEBUG
+#ifdef DEBUG
+# define DEBUG_P(x...)  printf("DEBUG: "x)
+#else
+# define DEBUG_P(x...)
+#endif
+
 #define WINDOW_TITLE "Clock Display"
 #define SCREEN_WIDTH 800
 #define SCREEN_HEIGHT 480
@@ -87,11 +94,32 @@ void get_clock_data(struct clock_data *l)
 	}
 }
 
+int calculate_brightness(int midday_mins, int now_mins)
+{
+#define MIN_BRIGHTNESS 11
+#define MAX_BRIGHTNESS 255
+#define MIN_BRIGHT_VIRTUAL (-150)
+#define MAX_BRIGHT_VIRTUAL 400
+	int ret = 0;
+
+	DEBUG_P("midday %d, now %d minutes\n", midday_mins, now_mins);
+
+	ret = MAX_BRIGHT_VIRTUAL - ((MAX_BRIGHT_VIRTUAL - MIN_BRIGHT_VIRTUAL) * abs(now_mins - midday_mins)) / midday_mins;
+
+	if (ret < MIN_BRIGHTNESS)
+		ret = MIN_BRIGHTNESS;
+
+	if (ret > MAX_BRIGHTNESS)
+		ret = MAX_BRIGHTNESS;
+
+	return ret;
+}
+
 /**
  * Read clock's statistics from files and push them into shared data area for
  * display thread to pick up
  */
-void *read_stats(void* unused)
+void *read_stats(void* brightness_f_p)
 {
 	char buffer[32];
 	char *next = buffer;
@@ -99,6 +127,8 @@ void *read_stats(void* unused)
 	struct clock_data l;
 	memset(&l, 0, sizeof(l));
 
+	FILE* brightness_f = brightness_f_p;
+
 	while (1) {
 		/* Read sunrise, sunset */
 		if (f = fopen("/tmp/stats-sun", "r")) {
@@ -151,6 +181,38 @@ void *read_stats(void* unused)
 			}
 			fclose(f);
 		}
+
+		/* FIXME move decls to top */
+		int sunrise_hours = 0;
+		int sunrise_minutes = 0;
+		int sunset_hours = 0;
+		int sunset_minutes = 0;
+		if (   sscanf(l.sunrise_time, "%d:%d", &sunrise_hours, &sunrise_minutes) == 2
+		    && sscanf(l.sunset_time, "%d:%d", &sunset_hours, &sunset_minutes) == 2) {
+			sunrise_minutes += 60 * sunrise_hours;
+			sunset_minutes += 60 * sunset_hours;
+			int local_midday = (sunrise_minutes + sunset_minutes) / 2;
+
+			time_t t;
+			struct tm *time_s;
+			t = time(NULL);
+			if ((time_s = localtime(&t)) == NULL) {
+				/* FIXME error */
+				continue;
+			}
+
+			int brightness = calculate_brightness(local_midday, time_s->tm_hour*60 + time_s->tm_min);
+			DEBUG_P("Calculated brightness %d\n", brightness);
+			if (!brightness_f) {
+				DEBUG_P("Brightness file not open, not writing to it\n");
+			} else {
+				snprintf(buffer, sizeof(buffer), "%d\n", brightness);
+				if (fwrite(buffer, strlen(buffer), 1, brightness_f) != strlen(buffer)) {
+					perror("fwrite");
+				}
+			}
+		}
+
 		sem_wait(&data_lock);
 		publish_clock_data(&l);
 		sem_post(&data_lock);
@@ -275,9 +337,23 @@ int main(void)
 		return 1;
 	}
 
+	FILE* brightness_f = fopen("/sys/class/backlight/rpi_backlight/brightness", "w+");
+	if (!brightness_f) {
+		perror("fopen");
+	}
+
+	if (setgid(getgid()) < 0) {
+		perror("setgid");
+		return 1;
+	}
+	if (setuid(getuid()) < 0) {
+		perror("setuid");
+		return 1;
+	}
+
 	/* launch pthread */
 	pthread_t thread;
-	if (pthread_create(&thread, NULL, read_stats, NULL) != 0) {
+	if (pthread_create(&thread, NULL, read_stats, brightness_f) != 0) {
 		perror("pthread_create");
 		return 1;
 	}
-- 
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