Lower Active Window and Cycle Focus on the Same Monitor (X11)

lower-active-window.sh

#!/usr/bin/env bash
set -euo pipefail

DEBUG="${DEBUG:-0}"
LOG_FILE="${LOG_FILE:-$HOME/.cache/lower-cycle.log}"

mkdir -p "$(dirname "$LOG_FILE")"

ts() { date +'%H:%M:%S'; }
log()  { (( DEBUG >= 1 )) && printf '[%s] %s\n' "$(ts)" "$*" | tee -a "$LOG_FILE" >&2; }
log2() { (( DEBUG >= 2 )) && printf '[%s] %s\n' "$(ts)" "$*" | tee -a "$LOG_FILE" >&2; }

on_err() {
  local ec=$?
  printf '[%s] ERROR line=%s cmd=%q exit=%s\n' "$(ts)" "${BASH_LINENO[0]}" "$BASH_COMMAND" "$ec" | tee -a "$LOG_FILE" >&2
  exit "$ec"
}
trap on_err ERR

# ---------------------------
# Monitor model
# ---------------------------
declare -a MON_NAME MON_X MON_Y MON_W MON_H

load_monitors() {
  MON_NAME=(); MON_X=(); MON_Y=(); MON_W=(); MON_H=()

  while IFS= read -r line; do
    [[ -n "$line" ]] || continue

    local name geom w h x y
    name="$(awk '{print $2}' <<<"$line" | sed 's/^[+*]*//')"
    geom="$(awk '{print $3}' <<<"$line")"

    w="$(sed -n 's#^\([0-9]\+\)/.*#\1#p' <<<"$geom")"
    h="$(sed -n 's#^[0-9]\+/.*x\([0-9]\+\)/.*#\1#p' <<<"$geom")"
    x="$(sed -n 's#^.*+\([0-9]\+\)+\([0-9]\+\)$#\1#p' <<<"$geom")"
    y="$(sed -n 's#^.*+\([0-9]\+\)+\([0-9]\+\)$#\2#p' <<<"$geom")"

    if [[ -n "$name" && -n "$w" && -n "$h" && -n "$x" && -n "$y" ]]; then
      MON_NAME+=("$name"); MON_W+=("$w"); MON_H+=("$h"); MON_X+=("$x"); MON_Y+=("$y")
    fi
  done < <(xrandr --listmonitors 2>/dev/null | tail -n +2)

  if (( ${#MON_NAME[@]} == 0 )); then
    log "No monitors found via xrandr --listmonitors (monitor filtering disabled)."
    return 1
  fi

  log "Monitors:"
  for i in "${!MON_NAME[@]}"; do
    log "  [$i] ${MON_NAME[$i]}: ${MON_W[$i]}x${MON_H[$i]}+${MON_X[$i]}+${MON_Y[$i]}"
  done
}

monitor_for_point() {
  local px="$1" py="$2"
  for i in "${!MON_NAME[@]}"; do
    local x="${MON_X[$i]}" y="${MON_Y[$i]}" w="${MON_W[$i]}" h="${MON_H[$i]}"
    if (( px >= x && px < x + w && py >= y && py < y + h )); then
      printf '%s' "$i"
      return 0
    fi
  done
  return 1
}

# ---------------------------
# Window helpers
# ---------------------------
window_geom() {
  local wid_dec="$1"
  local out
  out="$(xdotool getwindowgeometry --shell "$wid_dec" 2>/dev/null || true)"
  [[ -n "$out" ]] || return 1

  local X="" Y="" WIDTH="" HEIGHT=""
  # shellcheck disable=SC1090
  source <(printf '%s\n' "$out")

  [[ -n "${X:-}" && -n "${Y:-}" && -n "${WIDTH:-}" && -n "${HEIGHT:-}" ]] || return 1
  printf '%s %s %s %s\n' "$X" "$Y" "$WIDTH" "$HEIGHT"
}

monitor_for_window_center() {
  local wid_dec="$1"
  local gx gy gw gh
  read -r gx gy gw gh < <(window_geom "$wid_dec")
  local cx=$((gx + gw / 2))
  local cy=$((gy + gh / 2))
  monitor_for_point "$cx" "$cy"
}

is_skippable_window() {
  local wid_hex="$1"
  local t
  t="$(xprop -id "$wid_hex" _NET_WM_WINDOW_TYPE 2>/dev/null || true)"
  grep -qE '_NET_WM_WINDOW_TYPE_(DOCK|DESKTOP)' <<<"$t"
}

window_title() {
  local wid_hex="$1"
  xprop -id "$wid_hex" _NET_WM_NAME 2>/dev/null \
    | sed -n 's/^.*= \(.*\)$/\1/p' \
    | sed 's/^"//; s/"$//'
}

window_class() {
  local wid_hex="$1"
  xprop -id "$wid_hex" WM_CLASS 2>/dev/null \
    | sed -n 's/^.*= \(.*\)$/\1/p'
}

# ---------------------------
# Stacking helpers
# ---------------------------
stacking_list_hex() {
  local raw
  raw="$(xprop -root _NET_CLIENT_LIST_STACKING 2>/dev/null || true)"
  [[ -n "$raw" ]] || return 1

  sed -n 's/^.*# //p' <<<"$raw" \
    | tr -d ',' \
    | tr ' ' '\n' \
    | sed '/^$/d'
}

find_index_in_array() {
  local needle="$1"; shift
  local i=0
  for item in "$@"; do
    [[ "$item" == "$needle" ]] && { printf '%s\n' "$i"; return 0; }
    ((i++))
  done
  return 1
}

pick_target_under_active_same_monitor() {
  local active_hex="$1"
  local active_mon_idx="${2:-}"

  mapfile -t stack_hex < <(stacking_list_hex)

  local idx
  idx="$(find_index_in_array "$active_hex" "${stack_hex[@]}")"

  log "Considering windows under active (nearest-under to bottom):"
  for ((j=idx-1; j>=0; j--)); do
    local cand_hex="${stack_hex[$j]}"
    local cand_dec="$((cand_hex))"
    local prefix="$cand_hex ($cand_dec)"

    if is_skippable_window "$cand_hex"; then
      log "  $prefix -> skip: DOCK/DESKTOP"
      continue
    fi

    if is_hidden_window "$cand_hex"; then
      log "  $prefix -> skip: hidden/minimized"
      continue
    fi


    # Workspace filter: only consider windows on current workspace, plus sticky
    if [[ -n "${curdesk:-}" ]]; then
      if ! same_workspace_or_sticky "$cand_hex" "$curdesk"; then
        log "  $prefix -> skip: other workspace"
        continue
      fi
    fi


    if (( ${#MON_NAME[@]} > 0 )) && [[ -n "$active_mon_idx" ]]; then
      local cand_mon_idx=""
      cand_mon_idx="$(monitor_for_window_center "$cand_dec" 2>/dev/null || true)"

      if [[ -z "$cand_mon_idx" ]]; then
        log "  $prefix -> skip: monitor unknown"
        continue
      fi
      if [[ "$cand_mon_idx" != "$active_mon_idx" ]]; then
        log "  $prefix -> skip: other monitor (${MON_NAME[$cand_mon_idx]})"
        continue
      fi
    fi
    if (( DEBUG >= 2 )); then
      local d; d="$(window_desktop "$cand_hex" || true)"
      log2 "  $prefix -> hidden state: $(window_net_wm_state "$cand_hex" | tr '\n' ' ') | $(window_wm_state "$cand_hex" | tr '\n' ' ')"
      log2 "  $prefix -> ACCEPT desk=${d:-?} class=$(window_class "$cand_hex") title=$(window_title "$cand_hex")"
    else
      log "  $prefix -> ACCEPT"
    fi

    printf '%s\n' "$cand_dec"
    return 0
  done
}

window_net_wm_state() {
  # arg: window id in hex (0x...)
  xprop -id "$1" _NET_WM_STATE 2>/dev/null || true
}

window_wm_state() {
  # arg: window id in hex (0x...)
  xprop -id "$1" WM_STATE 2>/dev/null || true
}

is_hidden_window() {
  # arg: window id in hex (0x...)
  local s

  # EWMH: hidden/minimized
  s="$(window_net_wm_state "$1")"
  if grep -q '_NET_WM_STATE_HIDDEN' <<<"$s"; then
    return 0
  fi

  # ICCCM fallback: IconicState == minimized
  s="$(window_wm_state "$1")"
  if grep -q 'IconicState' <<<"$s"; then
    return 0
  fi

  return 1
}


# ---------------------------
# Workspace helpers
# ---------------------------
current_desktop() {
  # prints an integer like 0,1,2...
  xprop -root _NET_CURRENT_DESKTOP 2>/dev/null \
    | awk -F' = ' '{print $2}' \
    | tr -d '\n'
}

window_desktop() {
  # arg: window id in hex (0x...)
  # prints: integer desktop index, or -1 for sticky, or empty if missing
  xprop -id "$1" _NET_WM_DESKTOP 2>/dev/null \
    | awk -F' = ' '{print $2}' \
    | tr -d '\n'
}

same_workspace_or_sticky() {
  # args: cand_hex, curdesk
  local cand_hex="$1" curdesk="$2"
  local desk
  desk="$(window_desktop "$cand_hex" || true)"
  [[ -n "$desk" ]] || return 1

  # Sticky windows often show as 0xFFFFFFFF or 4294967295; normalize to -1.
  if [[ "$desk" == "0xFFFFFFFF" || "$desk" == "4294967295" ]]; then
    return 0
  fi

  [[ "$desk" == "$curdesk" ]]
}


main() {
  : > "$LOG_FILE"  # truncate each run so it’s easy to inspect
  log "Starting (DEBUG=$DEBUG) PID=$$"

  local curdesk=""
  curdesk="$(current_desktop || true)"
  log "Current desktop: ${curdesk:-UNKNOWN}"


  local active_dec active_hex
  active_dec="$(xdotool getactivewindow)"
  active_hex="$(printf '0x%x' "$active_dec")"

  load_monitors || true

  local active_mon_idx=""
  if (( ${#MON_NAME[@]} > 0 )); then
    active_mon_idx="$(monitor_for_window_center "$active_dec" 2>/dev/null || true)"
  fi

  if [[ -n "$active_mon_idx" ]]; then
    log "Active window: $active_hex monitor=[${active_mon_idx}] ${MON_NAME[$active_mon_idx]}"
  else
    log "Active window: $active_hex monitor=UNKNOWN"
  fi

  local target_dec=""
  if xprop -root _NET_CLIENT_LIST_STACKING >/dev/null 2>&1; then
    target_dec="$(pick_target_under_active_same_monitor "$active_hex" "$active_mon_idx" || true)"
  else
    log "No _NET_CLIENT_LIST_STACKING available; will only lower."
  fi

  log "Lowering active window: $active_hex"
  xdo lower "$active_dec"

  if [[ -n "$target_dec" ]]; then
    log "Activating target window: $target_dec"
    xdotool windowactivate --sync "$target_dec"
  else
    log "No eligible target found; focus unchanged."
  fi
}

main "$@"

A robust X11 utility script that lowers the currently active window and automatically transfers focus to the next eligible window underneath it on the same physical monitor. The script uses the real X11 restack operation (xdo lower) to ensure correct stacking order, derives monitor boundaries from xrandr, and determines window-to-monitor assignment via window geometry rather than unreliable screen indices. It filters out non-interactive windows (docks, panels, desktops), guarantees repeatable cycling behavior, and includes optional debug logging to make all window-selection decisions transparent. Designed for multi-monitor setups and keyboard-driven workflows on X11-based Linux desktops. It's also workspace aware. It avoids switching to hidden windows.