Backlight: fix crash in #442

i3pystatus/backlight.py

@@ -20,6 +20,7 @@ class Backlight(File):
 
     settings = (
         ("format", "format string, formatters: brightness, max_brightness, percentage"),
+        ("format_no_backlight", "format string when no backlight file available"),
         ("backlight",
             "backlight, see `/sys/class/backlight/`. Supports glob expansion, i.e. `*` matches anything. "
             "If it matches more than one filename, selects the first one in alphabetical order"),
@@ -29,6 +30,7 @@ class Backlight(File):
 
     backlight = "*"
     format = "{brightness}/{max_brightness}"
+    format_no_backlight = "No backlight"
 
     base_path = "/sys/class/backlight/{backlight}/"
     components = {
@@ -43,7 +45,12 @@ class Backlight(File):
 
     def init(self):
         self.base_path = self.base_path.format(backlight=self.backlight)
-        self.base_path = sorted(glob.glob(self.base_path))[0]
+        backlight_entries = sorted(glob.glob(self.base_path))
+
+        if len(backlight_entries) == 0:
+            self.run = run_no_backlight
+
+        self.base_path = backlight_entries[0]
         self.has_xbacklight = shutil.which("xbacklight") is not None
 
         # xbacklight expects a percentage as parameter. Calculate the percentage
@@ -59,6 +66,23 @@ class Backlight(File):
                     self.step_size = 5  # default?
         super().init()
 
+    def run_no_backlight(self):
+        cdict = {
+            "brightness": -1,
+            "max_brightness": -1,
+            "percentage": -1
+        }
+
+        format = self.format_no_backlight
+        if not format:
+            format = self.format
+
+        self.data = cdict
+        self.output = {
+            "full_text": format.format(**cdict),
+            "color": self.color
+        }
+
     def lighter(self):
         if self.has_xbacklight:
             run_through_shell(["xbacklight", "-inc", str(self.step_size)])