pkgs/profpatsch/backlight: init

2 files changed, 55 insertions, 0 deletions

diff --git a/pkgs/profpatsch/backlight/backlight.py b/pkgs/profpatsch/backlight/backlight.py
new file mode 100755
index 00000000..d580260a
--- /dev/null
+++ b/pkgs/profpatsch/backlight/backlight.py
@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+# xbacklight uses a linear percentage,
+# but the backlight intensity is actually logarithmic *facepalm*.
+# So we read the current "percentage" given by xbacklight
+# and calculate the next step, base 2.
+
+import subprocess as sub
+import math
+import sys
+
+xbacklight = "xbacklight"
+
+def usage():
+    print("usage: backlight [inc|dec]", file=sys.stderr)
+    sys.exit(1)
+
+# read current value
+current_backlight = float(sub.run(xbacklight, stdout=sub.PIPE).stdout.strip())
+# find the actual value, base 2
+current_val = round(math.sqrt(current_backlight))
+
+if len(sys.argv) == 1: usage()
+else:
+    mode = sys.argv[1]
+
+# modify actual value
+if mode == "inc":
+    new_val = current_val + 1
+elif mode == "dec":
+    new_val = current_val - 1
+else:
+    usage()
+
+# clamp value
+new_backlight = min(10, max(0, new_val))
+
+# pow it again and set
+sub.run([xbacklight, "-set", str(math.pow(new_backlight, 2))])
diff --git a/pkgs/profpatsch/backlight/default.nix b/pkgs/profpatsch/backlight/default.nix
new file mode 100644
index 00000000..d2f40be0
--- /dev/null
+++ b/pkgs/profpatsch/backlight/default.nix
@@ -0,0 +1,17 @@
+{ stdenv, python3, xbacklight}:
+
+stdenv.mkDerivation rec {
+  name = "backlight";
+
+  src = ./backlight.py;
+  phases = [ "installPhase" "fixupPhase" ];
+
+  buildInputs = [ python3 ];
+
+  installPhase = ''
+    install -D ${src} $out/bin/backlight
+    substituteInPlace $out/bin/backlight \
+      --replace '"xbacklight"' '"${xbacklight}/bin/xbacklight"'
+  '';
+
+}