improve bin/isdarktty

1 files changed, 7 insertions, 6 deletions

diff --git a/bin/isdarktty b/bin/isdarktty
index 779f6c8..a09579b 100755
--- a/bin/isdarktty
+++ b/bin/isdarktty
@@ -1,13 +1,14 @@
 #!/bin/sh
 
-# Check darkness by computing luminance of the current terminal.
-# see https://en.wikipedia.org/wiki/Luma_(video)
+# Detect terminal darkness. Return 0 if dark, else 1.
 
-trap "stty $(stty -g)" EXIT
-stty raw -echo min 0 time 0
-printf '\e]11;?\e\\'
-sleep 0.01
+trap "stty $(stty -g)" EXIT  # restore terminal settings at exit
+stty raw -echo min 0 time 0  # set terminal in raw mode for query
+printf '\e]11;?\e\\'         # xterm escape sequence to get bg color
+sleep 0.01                   # 10ms delay to let terminal respond
 
+# parse terminal response in form of: ...rgb:cf00/ff00/ff00...
+# luma equation adapted from https://en.wikipedia.org/wiki/Luma_(video)
 awk -v FS='' -v hex=123456789abcdef '{
 	r = (16 * index(hex, $10) + index(hex, $11)) / 255
 	g = (16 * index(hex, $15) + index(hex, $16)) / 255