From c771e2d2e69dcde230eaa4ca4f8dd45de441ebbc Mon Sep 17 00:00:00 2001
From: Igor Kolokolnikov <igor@kolokolnikov.dev>
Date: Fri, 25 Sep 2026 14:55:12 -0700
Subject: [PATCH] Initial support for backlight control on sleep, needs more
 work.

---
 slock.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 120 insertions(+), 12 deletions(-)

diff --git a/slock.c b/slock.c
index 51cf84c..8941ba6 100644
--- a/slock.c
+++ b/slock.c
@@ -19,6 +19,7 @@
 #include <sys/mman.h> /* mmap */
 #include <sys/timerfd.h> /* timerfd_create */
 #include <sys/types.h>
+#include <dirent.h> /* opendir, closedir, readdir */
 #include <X11/extensions/Xrandr.h>
 #include <X11/extensions/dpms.h>
 #include <X11/keysym.h>
@@ -109,13 +110,13 @@ die(const char *errstr, ...)
     exit(1);
 }
 
-int round_float_to_int(float real32)
+static int round_float_to_int(float real32)
 {
     int result = (int)roundf(real32);
     return result;
 }
 
-int str_len(const char *str)
+static int str_len(const char *str)
 {
     int i = 0;
     while(*(str++) != '\0') {
@@ -124,6 +125,29 @@ int str_len(const char *str)
     return i;
 }
 
+static int str_contains(const char *str, const char *value)
+{
+    int strlen, vallen, i, ii, matches;
+
+    strlen = str_len(str);
+    vallen = str_len(value);
+
+    matches = 0;
+
+    for(i = 0; i <= strlen-vallen && !matches; i++) {
+        for(ii = 0; ii < vallen; ii++) {
+            if(str[i+ii] == value[ii]) {
+                matches = 1;
+            } else {
+                matches = 0;
+                break;
+            }
+        }
+    }
+
+    return matches;
+}
+
 unsigned long long millis()
 {
     struct timespec ts;
@@ -603,6 +627,89 @@ static void dpms_enable(Display *dpy, struct dpms_state *state)
     }
 }
 
+struct keyboard_backlight_state {
+    int available;
+    int brightness;
+    int fd;
+};
+
+static struct keyboard_backlight_state get_keyboard_backlight_state()
+{
+
+    static char bl_entry[1024];
+    char *leds;
+    DIR *d;
+
+    struct keyboard_backlight_state bl_state;
+    memset(&bl_state, 0, sizeof(bl_state));
+
+    leds = "/sys/class/leds";
+    d = opendir(leds);
+    if(d) {
+        struct dirent *entry;
+        while((entry = readdir(d)) != 0) {
+            if(str_contains(entry->d_name, "kbd_backlight")) {
+                static char read_buf[32];
+                int fd;
+
+                snprintf(bl_entry, 1024,
+                         "%s/%s/brightness", leds, entry->d_name);
+
+                fd = open(bl_entry, O_RDWR);
+                if(fd != -1) {
+                    int read_amnt, s;
+                    char *endptr;
+                    long num;
+
+                    read_amnt = 0;
+                    do {
+                        s = read(fd, read_buf+read_amnt, 32-read_amnt);
+                        if(s == -1)
+                            break;
+                        read_amnt += s;
+                    } while(s != 0);
+
+                    if(s != -1) {
+                        read_buf[read_amnt] = '\0';
+
+                        num = strtol(read_buf, &endptr, 10);
+                        if(!(errno == ERANGE || endptr == read_buf)) {
+                            bl_state.available = 1;
+                            bl_state.fd = fd;
+                            bl_state.brightness = num;
+                        }
+                    }
+                }
+
+                break;
+            }
+        }
+        closedir(d);
+    }
+
+    return bl_state;
+}
+
+static void
+reset_keyboard_backlight(struct keyboard_backlight_state *bl_state)
+{
+    static char buf[512];
+    if(bl_state->available) {
+        snprintf(buf, sizeof(buf), "%d\n", bl_state->brightness);
+        write(bl_state->fd, buf, str_len(buf));
+    }
+}
+
+static void
+set_keyboard_backlight_off(struct keyboard_backlight_state *bl_state)
+{
+    if(bl_state->available) {
+        char buf[512];
+        snprintf(buf, sizeof(buf), "%d\n", 0);
+        write(bl_state->fd, buf, str_len(buf));
+    }
+}
+
 static void update_timerfd(int tfd)
 {
     time_t now;
@@ -623,7 +730,7 @@ static void update_timerfd(int tfd)
 static void
 readpw(struct arena *arena,
        Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
-       const char *hash)
+       const char *hash, struct keyboard_backlight_state *bl_state)
 {
     XRRScreenChangeNotifyEvent *rre;
     char buf[32], passwd[256], *inputhash;
@@ -653,12 +760,6 @@ readpw(struct arena *arena,
 
     dpms_disable(dpy, &dpms_state);
 
-    FT_Library main_font_library;
-    FT_Face main_font_face;
-
-    FT_Library secondary_font_library;
-    FT_Face secondary_font_face;
-
     if(!load_fonts(&fonts))
         die("slock: load_fonts\n");
 
@@ -804,10 +905,13 @@ readpw(struct arena *arena,
             }
         }
 
-        if(dson)
+        if(dson) {
+            reset_keyboard_backlight(bl_state);
             set_screen_on(dpy);
-        else
+        } else {
+            set_keyboard_backlight_off(bl_state);
             set_screen_off(dpy);
+        }
 
         render_screen(arena,
                       dpy, locks,
@@ -835,6 +939,7 @@ readpw(struct arena *arena,
             if(ret == 0) {
                 dson = 0;
                 set_screen_off(dpy);
+                set_keyboard_backlight_off(bl_state);
             } else if(ret > 0 && FD_ISSET(xfd, &fds)) {
             } else if(ret > 0 && FD_ISSET(tfd, &fds)) {
             }
@@ -1010,6 +1115,9 @@ main(int argc, char **argv) {
     if (!DPMSQueryExtension(dpy, &event_base, &error_base))
         die("slock: dpms extension is not supported\n");
 
+    struct keyboard_backlight_state bl_state =
+        get_keyboard_backlight_state();
+
     /* drop privileges */
     if (setgroups(0, NULL) < 0)
         die("slock: setgroups: %s\n", strerror(errno));
@@ -1050,7 +1158,7 @@ main(int argc, char **argv) {
 
     /* everything is now blank. Wait for the correct password */
     struct arena arena = arena_init(bf, GB(1));
-    readpw(&arena, dpy, &rr, locks, nscreens, hash);
+    readpw(&arena, dpy, &rr, locks, nscreens, hash, &bl_state);
 
     return 0;
 }