monitor input availability through udev events

1 files changed, 45 insertions, 16 deletions

diff --git a/panel.py b/panel.py
index 34beed3..9efef29 100755
--- a/panel.py
+++ b/panel.py
@@ -3,6 +3,7 @@
 # Copyright 2024 David Vazgenovich Shakaryan
 
 import glob
+import os
 import subprocess
 import threading
 import time
@@ -150,26 +151,52 @@ class ModHLWM(Mod):
     def process_cmd(self, cmd):
         subprocess.run(('herbstclient', *cmd.split()))
 
-class ModNoKBD(Mod):
-    def __init__(self):
+class ModInputUnavail(Mod):
+    def __init__(self, path, label=''):
         super().__init__()
-        self.prev = True
+        self.path = path
+        self.label = label
 
     def work(self):
-        while True:
-            has_kbd = bool(glob.glob('/dev/input/by-id/*-kbd'))
-            if has_kbd != self.prev:
-                if has_kbd:
-                    buf = None
-                else:
-                    buf = f'%{{B#a03000}}{spacing()}NO KBD{spacing()}%{{B-}}'
+        p = subprocess.Popen(
+            ('udevadm', 'monitor', '-ups', 'input'),
+            stdout=subprocess.PIPE, text=True)
 
-                self.prev = has_kbd
-                with self.cv:
-                    self.out = buf
-                    self.cv.notify()
+        self._update_state(os.path.exists(self.path))
 
-            time.sleep(1)
+        building = False
+        for line in iter(p.stdout.readline, ''):
+            line = line.rstrip()
+
+            if not building and line.startswith('UDEV'):
+                building = True
+                e = {}
+            elif building:
+                if '=' in line:
+                    k, v = line.split('=', 1)
+                    e[k] = v
+                else:
+                    building = False
+                    if e:
+                        self._process_event(e)
+
+    def _process_event(self, e):
+        if (action := e.get('ACTION')) and (paths := e.get('DEVLINKS')):
+            if self.path in paths.split(' '):
+                if action == 'add':
+                    self._update_state(True)
+                elif action == 'remove':
+                    self._update_state(False)
+
+    def _update_state(self, avail):
+        if avail:
+            buf = None
+        else:
+            buf = f'%{{B#a03000}}{spacing()}{self.label}{spacing()}%{{B-}}'
+
+        with self.cv:
+            self.out = buf
+            self.cv.notify()
 
 class Bar:
     def __init__(self, *mods):
@@ -216,7 +243,9 @@ class Bar:
 Bar(
     ModHLWM(),
     ModRight(),
-    ModNoKBD(),
+    ModInputUnavail(
+        '/dev/input/by-id/usb-HID_Keyboard_HID_Keyboard-event-kbd',
+        label='NO KEYBOARD'),
     ModSpacer(n=2),
     ModDate(
         fmts=('%Y-%m-%d %H:%M:%S', '%H:%M'),