From 91952b8fd95da215a6404cffb6f96b85d18fe4a2 Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Wed, 3 Nov 2021 09:45:36 +0100
Subject: Xsession: show notifications on screen brightness changes

---
 bin/brightness_monitor | 40 ++++++++++++++++++++++++++++++++++++++++
 desktop.conf.yaml      |  1 +
 dotfiles/Xsession      |  5 +++++
 3 files changed, 46 insertions(+)
 create mode 100755 bin/brightness_monitor

diff --git a/bin/brightness_monitor b/bin/brightness_monitor
new file mode 100755
index 0000000..a8617e0
--- /dev/null
+++ b/bin/brightness_monitor
@@ -0,0 +1,40 @@
+#!/usr/bin/python3
+
+import notify2
+import os
+import subprocess
+import sys
+
+if len(sys.argv) < 2:
+    sys.stdout.write('Usage: %s /sys/.../<backlight dir>/\n')
+    sys.exit(0)
+
+path = sys.argv[1]
+
+with open(os.path.join(path, 'max_brightness'), 'r') as f:
+    brightness_max = float(f.read().strip())
+
+notify2.init(os.path.basename(sys.argv[0]))
+
+notification = notify2.Notification('Brightness')
+
+inotify_cmd = ['inotifywait', '--monitor', '--event=close_write',
+               os.path.join(path, 'brightness')]
+
+child = subprocess.Popen(inotify_cmd, stdout = subprocess.PIPE, bufsize = 0)
+
+while True:
+    # wait for updates
+    child.stdout.read(4096)
+    if child.poll() is not None:
+        notification.message = 'inotify monitor has terminated'
+        notification.set_urgency(notify2.URGENCY_CRITICAL)
+        notification.show()
+        sys.stderr.write(notification.message + '\n')
+        break
+
+    with open(os.path.join(path, 'brightness'), 'r') as f:
+        brightness = float(f.read().strip())
+
+    notification.message = '%d%%' % (100 * brightness / brightness_max)
+    notification.show()
diff --git a/desktop.conf.yaml b/desktop.conf.yaml
index fa2eb13..81ade61 100644
--- a/desktop.conf.yaml
+++ b/desktop.conf.yaml
@@ -4,6 +4,7 @@
 
 - link:
     ~/.config/mpv/config: dotfiles/mpv
+    ~/.local/bin/brightness_monitor:  bin/brightness_monitor
     ~/.local/bin/ssh_sk_clean:  bin/ssh_sk_clean
     ~/.local/bin/udev_match:    bin/udev_match
     ~/.urxvt/ext/reselect: urxvt/reselect/reselect
diff --git a/dotfiles/Xsession b/dotfiles/Xsession
index 72065a5..3d2a716 100644
--- a/dotfiles/Xsession
+++ b/dotfiles/Xsession
@@ -20,6 +20,11 @@ udev_match --subsystem=hidraw --match=ACTION=remove --match=ID_FIDO_TOKEN=1 ssh_
 udev_match --subsystem=hidraw --match=ACTION=add    --match=ID_FIDO_TOKEN=1 \
     "ssh-add -K || notify-send -u critical 'Error adding FIDO2 keys to SSH agent' 'Wrong PIN?'" &
 
+# show notifications on brightness changes
+for d in /sys/class/backlight/*; do
+    brightness_monitor "$d" &
+done
+
 # source the machine-local configuration
 [ -r "$HOME/.config/Xsession_local" ] && . "$HOME/.config/Xsession_local"
 
-- 
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