omarchycn/bin/omarchy-chromium-theme-host

#!/bin/bash
# omarchy:summary=Native messaging host: push the active Omarchy theme to Chromium web apps
# omarchy:hidden=true

# Native messaging host for the Omarchy theme bridge.
#
# Reads the active Omarchy theme and reports background / foreground / accent /
# selection / browser-chrome colors to a web-app extension as length-prefixed
# JSON on stdout. It's a shared bridge keyed by name (com.omarchy.theme): any
# bundled web-app extension that wants to follow the theme connects to it and
# lists its ID in the host manifest's allowed_origins.
#
# This host is PUSH-ONLY: it never parses inbound messages. That's deliberate.
# Reading Chromium's length-prefixed framing in bash means blocking in
# `head -c4`, which a trap cannot interrupt — so a signal-driven wakeup would
# need a background reader plus a FIFO. Instead we let omarchy's theme-set hook
# signal us with SIGUSR1 (see bin/omarchy-theme-set) and drop inbound
# stdio entirely. The extension gets a push on connect and a push on every
# theme change, which is all it ever needs.
#
# This differs from Omarchy's other bundled hosts (omarchy-chromium-copy-url-host,
# -ytdlp-host): those are one-shot — read a frame, act, exit. Theme-following is
# the inverse direction (system -> extension), so we stay alive to push; only
# their framing idioms carry over, not their structure.
#
# Because it ships in-tree, `omarchy-theme-set` runs the refresh command on every
# switch, so no polling fallback is needed (the standalone AUR build of this host
# carries one for old Omarchy).

set -uo pipefail

# Omarchy 4+ keeps the active theme state here; theme/ is a directory Omarchy
# replaces wholesale on every switch (same layout `omarchy-theme-set` writes).
CURRENT="$HOME/.local/state/omarchy/current"

# Pidfiles live here so the theme-set.d hook can SIGUSR1 every running host.
RUNDIR="$XDG_RUNTIME_DIR/omarchy-theme"
PIDFILE="$RUNDIR/$$.pid"

WATCHDOG_PID=""

# ---------------------------------------------------------------- lifecycle --

cleanup() {
  rm -f "$PIDFILE"
  [[ -n $WATCHDOG_PID ]] && kill "$WATCHDOG_PID" 2>/dev/null
  return 0
}

# ------------------------------------------------------------------ parsing --

trim() {
  local s="$1"
  s="${s#"${s%%[![:space:]]*}"}"
  s="${s%"${s##*[![:space:]]}"}"
  printf '%s' "$s"
}

read_text() {
  [[ -f $1 ]] || return 0
  local text
  text=$(<"$1") || return 0
  trim "$text"
}

# The terminal background lives under [colors.primary] in the theme's
# alacritty.toml. Only that section counts — other sections define their own
# `background` keys that would otherwise match.
parse_alacritty_bg() {
  local file="$1" line s in_primary=0
  [[ -f $file ]] || return 0
  while IFS= read -r line || [[ -n $line ]]; do
    s=$(trim "$line")
    if [[ $s == \[* ]]; then
      if [[ $s == "[colors.primary]" ]]; then in_primary=1; else in_primary=0; fi
      continue
    fi
    if ((in_primary)) && [[ $s =~ ^background[[:space:]]*=[[:space:]]*\"(#[0-9a-fA-F]{6,8})\" ]]; then
      printf '%s' "${BASH_REMATCH[1]}"
      return 0
    fi
  done <"$file"
}

# colors.toml is a flat list of `name = "#rrggbb"` pairs. Populates COLORS.
declare -A COLORS=()
parse_colors_toml() {
  local file="$1" line s
  COLORS=()
  [[ -f $file ]] || return 0
  while IFS= read -r line || [[ -n $line ]]; do
    s=$(trim "$line")
    if [[ $s =~ ^([A-Za-z0-9_]+)[[:space:]]*=[[:space:]]*\"(#[0-9a-fA-F]{6,8})\" ]]; then
      COLORS["${BASH_REMATCH[1]}"]="${BASH_REMATCH[2]}"
    fi
  done <"$file"
}

# omarchy ships the browser chrome color as 'r,g,b' decimal CSV in chromium.theme.
# Most stock themes omit the file — omarchy-theme-set-browser then falls back to
# #1c2027, but we return empty and let the extension pick its own fallback so it
# can be theme-aware about the choice.
parse_chromium_theme() {
  local file="$1" text r g b extra c
  [[ -f $file ]] || return 0
  text=$(<"$file") || return 0
  text=$(trim "$text")
  IFS=, read -r r g b extra <<<"$text"
  [[ -n ${extra:-} ]] && return 0
  r=$(trim "${r:-}") g=$(trim "${g:-}") b=$(trim "${b:-}")
  for c in "$r" "$g" "$b"; do
    [[ $c =~ ^[0-9]+$ ]] || return 0
    ((c >= 0 && c <= 255)) || return 0
  done
  printf '#%02x%02x%02x' "$r" "$g" "$b"
}

# --------------------------------------------------------------------- JSON --

json_escape() {
  local s="$1"
  s="${s//\\/\\\\}"
  s="${s//\"/\\\"}"
  s="${s//$'\n'/\\n}"
  s="${s//$'\r'/\\r}"
  s="${s//$'\t'/\\t}"
  printf '%s' "$s"
}

# Emit a JSON string, or bare null when empty, so the extension can tell "theme
# didn't define this color" from "empty string".
json_value() {
  if [[ -z ${1:-} ]]; then
    printf 'null'
  else
    printf '"%s"' "$(json_escape "$1")"
  fi
}

build_state() {
  local name bg fg accent selection chrome

  name=$(read_text "$CURRENT/theme.name")
  bg=$(parse_alacritty_bg "$CURRENT/theme/alacritty.toml")
  parse_colors_toml "$CURRENT/theme/colors.toml"
  chrome=$(parse_chromium_theme "$CURRENT/theme/chromium.theme")

  [[ -z $bg ]] && bg="${COLORS[background]:-}"
  [[ -z $bg ]] && bg="#1e1e2e" # last-resort fallback

  fg="${COLORS[foreground]:-}"
  accent="${COLORS[accent]:-}"
  selection="${COLORS[selection_background]:-}"

  # No day/night flag by design — the extension decides dark vs. light purely
  # from the WCAG relative luminance of bg.
  printf '{"theme_name":%s,"bg":%s,"fg":%s,"accent":%s,"selection_bg":%s,"chrome":%s}' \
    "$(json_value "$name")" \
    "$(json_value "$bg")" \
    "$(json_value "$fg")" \
    "$(json_value "$accent")" \
    "$(json_value "$selection")" \
    "$(json_value "$chrome")"
}

# ------------------------------------------------------------------ framing --

# Chromium expects each message prefixed with its byte length as a native-endian
# (little, on every platform we target) uint32.
emit() {
  local json="$1" len
  len=$(LC_ALL=C printf '%s' "$json" | wc -c)
  printf '%b%s' \
    "\\x$(printf '%02x' $((len & 0xff)))\\x$(printf '%02x' $((len >> 8 & 0xff)))\\x$(printf '%02x' $((len >> 16 & 0xff)))\\x$(printf '%02x' $((len >> 24 & 0xff)))" \
    "$json" || exit 0 # stdout closed: the browser is gone
}

emit_theme() {
  local state
  state=$(build_state) || return 0
  emit "$state"
}

# --------------------------------------------------------------------- main --

main() {
  local starttime

  trap cleanup EXIT
  # Arm signal handlers before publishing the pidfile so refresh cannot signal
  # the host during a window where USR1 still has its default fatal disposition.
  trap 'exit 0' TERM INT
  trap 'emit_theme' USR1

  mkdir -p "$RUNDIR"
  starttime=$(awk '{print $22}' "/proc/$$/stat")
  [[ -n $starttime ]] || exit 1
  printf '%s %s\n' "$$" "$starttime" >"$PIDFILE"

  # Push the current theme immediately on connect, before arming the watchdog —
  # if stdin is already at EOF the watchdog fires at once, and we'd otherwise be
  # killed before saying anything.
  emit_theme

  # The browser talks to us by closing the pipe, not by sending anything we care
  # about. Drain stdin so its writes never block, and exit when it hangs up.
  #
  # The `<&3` is load-bearing. Bash gives every background job /dev/null as stdin
  # unless it's redirected explicitly, so a bare read loop here would see EOF
  # instantly and kill us right after the first push — leaving the extension in a
  # reconnect loop. Duplicating the real stdin onto fd 3 overrides the default.
  exec 3<&0
  (while IFS= read -r; do :; done <&3; kill -TERM "$$" 2>/dev/null) &
  WATCHDOG_PID=$!

  # Stay alive until the browser closes the pipe. A SIGUSR1 interrupts `wait`,
  # runs the USR1 trap to push, and we resume waiting; when the watchdog exits
  # (browser gone) `wait` succeeds and we fall through to the EXIT trap.
  while ! wait "$WATCHDOG_PID"; do :; done
}

if [[ ${BASH_SOURCE[0]} == "$0" ]]; then
  main "$@"
fi