mirror of
https://github.com/dnlbauer/dotfiles.git
synced 2026-09-10 13:35:30 +00:00
86 lines
2.8 KiB
Bash
86 lines
2.8 KiB
Bash
#!/bin/sh
|
|
# term-background: print "light" or "dark" for the current terminal.
|
|
#
|
|
# Asks the terminal for its background color with the OSC 11 escape sequence,
|
|
# converts the reply to perceived luminance, and prints "light" or "dark".
|
|
# Prints "dark" (the safe default) when the terminal does not answer.
|
|
#
|
|
# All terminal I/O happens on /dev/tty, so this is safe inside $(...).
|
|
#
|
|
# Works locally and over SSH (the query reaches whichever real terminal draws
|
|
# the screen). Inside tmux/screen the multiplexer may answer instead of the
|
|
# outer terminal, so detection can be wrong there; override it with
|
|
# export TERM_BACKGROUND=light # or dark
|
|
# in ~/.environment.local on that machine.
|
|
#
|
|
# Tune the per-attempt wait via TERM_BACKGROUND_TIMEOUT (tenths of a second)
|
|
# and the number of attempts via TERM_BACKGROUND_ATTEMPTS. We poll rather than
|
|
# do a single fixed-length read because on a freshly booted WSL instance the
|
|
# very first terminal's OSC 11 reply can arrive well after a short window
|
|
# closes; if we restored cooked/echo mode by then, the late reply leaks onto
|
|
# the screen (and into the shell's input buffer) as literal text. Staying in
|
|
# raw/no-echo mode across multiple short attempts lets a slow first reply
|
|
# still be captured silently instead of leaking.
|
|
|
|
# Need a controlling terminal to talk to.
|
|
[ -t 0 ] || { echo dark; exit 0; }
|
|
exec 3<>/dev/tty || { echo dark; exit 0; }
|
|
|
|
saved=$(stty -g <&3 2>/dev/null) || { echo dark; exit 0; }
|
|
stty raw -echo min 0 time "${TERM_BACKGROUND_TIMEOUT:-4}" <&3 2>/dev/null
|
|
|
|
printf '\033]11;?\033\\' >&3 # OSC 11 query
|
|
|
|
answer=""
|
|
attempts="${TERM_BACKGROUND_ATTEMPTS:-3}"
|
|
i=0
|
|
while [ "$i" -lt "$attempts" ]; do
|
|
answer="$answer$(dd bs=64 count=1 <&3 2>/dev/null)"
|
|
# A full "rgb:RRRR/GGGG/BBBB" reply has two '/' separators; stop as soon
|
|
# as we have them instead of waiting out every remaining attempt.
|
|
rest=${answer#*rgb:}
|
|
if [ "$rest" != "$answer" ]; then
|
|
tmp=$rest
|
|
count=0
|
|
while [ "$tmp" != "${tmp#*/}" ]; do
|
|
count=$((count + 1))
|
|
tmp=${tmp#*/}
|
|
done
|
|
[ "$count" -ge 2 ] && break
|
|
fi
|
|
i=$((i + 1))
|
|
done
|
|
|
|
stty "$saved" <&3 2>/dev/null # restore before anything else
|
|
exec 3>&-
|
|
|
|
# Expected reply: ESC ] 11 ; rgb:RRRR/GGGG/BBBB (ESC \ | BEL)
|
|
case "$answer" in
|
|
*rgb:*) ;;
|
|
*) echo dark; exit 0 ;;
|
|
esac
|
|
|
|
rgb=${answer#*rgb:} # RRRR/GGGG/BBBB<terminator>
|
|
r=${rgb%%/*}; rgb=${rgb#*/}
|
|
g=${rgb%%/*}; rgb=${rgb#*/}
|
|
b=$rgb
|
|
|
|
# Keep the most-significant two hex digits of each component.
|
|
r=${r%"${r#??}"}
|
|
g=${g%"${g#??}"}
|
|
b=${b%"${b#??}"}
|
|
|
|
case "$r$g$b" in
|
|
""|*[!0-9a-fA-F]*) echo dark; exit 0 ;;
|
|
esac
|
|
|
|
r=$(( 0x$r )); g=$(( 0x$g )); b=$(( 0x$b ))
|
|
|
|
# Rec. 601 perceived luminance, 0-255. Over half => light.
|
|
lum=$(( (r * 299 + g * 587 + b * 114) / 1000 ))
|
|
if [ "$lum" -gt 127 ]; then
|
|
echo light
|
|
else
|
|
echo dark
|
|
fi
|