[bl2-split] / bl2-splitscreen.sh

#!/usr/bin/env bash
# ---------------------------------------------------------------------------
# Borderlands 2 - two-player split screen on Linux
#
# Borderlands 2 has NO native PC split screen, so this launches TWO independent
# instances that connect over Goldberg's emulated Steam LAN. Each instance gets
# its own save, its own Goldberg identity, one controller, and half the screen
# (gamescope), auto-tiled side-by-side on KDE Plasma (KWin).
#
# Two build layouts are supported and AUTO-DETECTED:
#   * native  - the Aspyr native Linux port (ELF `Borderlands2`)         -> no Proton
#   * proton  - the Windows build (`Binaries/Win32/Borderlands2.exe`)    -> umu/Proton
# Force one with:  MODE=native|proton ./bl2-splitscreen.sh ...
#
# Usage:
#   ./bl2-splitscreen.sh check     # verify prerequisites for the detected mode
#   ./bl2-splitscreen.sh setup     # build the two patched game copies
#   ./bl2-splitscreen.sh run       # launch both halves + tile them
#   ./bl2-splitscreen.sh tile      # (re)tile the two windows on KDE
#   ./bl2-splitscreen.sh clean     # remove generated copies (not the game)
# ---------------------------------------------------------------------------
set -uo pipefail

# ============================ CONFIG =======================================
GAME_DIR="/home/max/.local/share/Steam/steamapps/common/Borderlands 2"
APPID=49520
BASE="/home/max/Games/bl2-split"

# --- Display geometry (per-player render size GW/GH and window position GX/GY) --
# Monitors are read from KDE in LOGICAL px as "X,Y WxH", sorted left-to-right.
_mons=$(kscreen-doctor -o 2>/dev/null | sed 's/\x1b\[[0-9;]*m//g' \
  | awk '/^Output:/{e=0} /enabled/{e=1} /Geometry:/&&e{print $2,$3}' | sort -t, -k1 -n)
_mi=1
while read -r _pos _size; do
  [ -z "$_pos" ] && continue
  _MX[$_mi]=${_pos%,*}; _MY[$_mi]=${_pos#*,}
  _MW[$_mi]=${_size%x*}; _MH[$_mi]=${_size#*x}
  _mi=$((_mi+1))
done <<< "$_mons"
MON_COUNT=$((_mi-1))
[ "${MON_COUNT:-0}" -ge 1 ] 2>/dev/null || { _MW[1]=2560; _MH[1]=1440; _MX[1]=0; _MY[1]=0; MON_COUNT=1; }

# DISPLAY_MODE:
#   dual  (default when >=2 monitors) -> each player gets a whole monitor, "fullscreen".
#   split (1 monitor) -> both on one monitor, side-by-side. Each half is 16:9 and
#         vertically centered, because a tall 8:9 window clips BL2's landscape UI,
#         and a full-width window would trip BL2 into exclusive fullscreen.
if [ "$MON_COUNT" -ge 2 ]; then DISPLAY_MODE="${DISPLAY_MODE:-dual}"; else DISPLAY_MODE="${DISPLAY_MODE:-split}"; fi

if [ "$DISPLAY_MODE" = dual ]; then
  GW[1]=${_MW[1]}; GH[1]=${_MH[1]}; GX[1]=${_MX[1]}; GY[1]=${_MY[1]}
  GW[2]=${_MW[2]}; GH[2]=${_MH[2]}; GX[2]=${_MX[2]}; GY[2]=${_MY[2]}
else
  _hw=$(( ${_MW[1]} / 2 )); _hh=$(( _hw * 9 / 16 ))
  [ "$_hh" -gt "${_MH[1]}" ] && _hh=${_MH[1]}
  _wy=$(( ${_MY[1]} + (${_MH[1]} - _hh) / 2 ))
  GW[1]=$_hw; GH[1]=$_hh; GX[1]=${_MX[1]};              GY[1]=$_wy
  GW[2]=$_hw; GH[2]=$_hh; GX[2]=$(( ${_MX[1]} + _hw )); GY[2]=$_wy
fi

# Controllers, matched by STABLE /dev/input/by-id names (survive replug/reboot).
P1_PAD_GLOB="/dev/input/by-id/*Microsoft_Controller_*-event-joystick"   # Xbox Series S|X (wired)
P2_PAD_GLOB="/dev/input/by-id/*Wireless_Receiver*-event-joystick"       # Xbox 360 Wireless Receiver
P1_VIDPID="0x045e/0x0b12"    # Xbox Series S|X            (SDL hint; used in proton mode)
P2_VIDPID="0x045e/0x0719"    # Xbox 360 Wireless Receiver

# Controller isolation: "bwrap" (mask other pad's /dev nodes; backend-agnostic)
# or "sdl" (VID/PID hint; only works for SDL games). Default depends on MODE:
#   native  -> bwrap  (the Aspyr binary is NOT SDL; the hint does nothing)
#   proton  -> sdl    (Proton is SDL-based; avoids bwrap<->pressure-vessel nesting)
ISOLATION="${ISOLATION:-}"

# Proton build for umu (proton mode). Empty = umu auto-selects/downloads UMU-Proton.
PROTONPATH="${PROTONPATH:-}"

# Native mode: the 2012 Aspyr binary must run inside the Steam scout runtime (the
# old libs it was built against) with the CLASSIC Mr_Goldberg emu. gbe_fork (both
# experimental and regular) segfaults this binary; classic goldberg works.
NATIVE_RUNTIME="${NATIVE_RUNTIME:-/home/max/.steam/steam/ubuntu12_32/steam-runtime/run.sh}"

# Seconds after launch before the windows are moved onto their screens (long enough
# for both to load past the resize-y splash). You can always re-run `.../tile`.
SPLASH_WAIT="${SPLASH_WAIT:-30}"

# Seconds between launching Player 1 and Player 2. 0 = both at once (this machine is
# fast enough). Native mode can be crash-prone launching both together - set e.g.
# STAGGER=25 there if the 2nd instance dies on startup.
STAGGER="${STAGGER:-0}"
# ===========================================================================

c_red=$'\e[31m'; c_grn=$'\e[32m'; c_yel=$'\e[33m'; c_dim=$'\e[2m'; c_rst=$'\e[0m'
say()  { printf '%s\n' "$*"; }
ok()   { printf '%s✓%s %s\n' "$c_grn" "$c_rst" "$*"; }
warn() { printf '%s!%s %s\n' "$c_yel" "$c_rst" "$*"; }
die()  { printf '%s✗ %s%s\n' "$c_red" "$*" "$c_rst" >&2; exit 1; }
# Loud, unmissable, bold-bright-yellow banner. Each arg is one line (keep it CAPS).
banner() {
  local b=$'\e[1;93m' r=$'\e[0m' bar="############################################################" l
  printf '\n%s%s%s\n' "$b" "$bar" "$r"
  for l in "$@"; do printf '%s##  %-54s##%s\n' "$b" "$l" "$r"; done
  printf '%s%s%s\n\n' "$b" "$bar" "$r"
}

# -------------------------------------------------------- mode detection ---
WIN_EXE_REL="Binaries/Win32/Borderlands2.exe"
NATIVE_BIN="Borderlands2"
detect_mode() {
  if [ -n "${MODE:-}" ]; then echo "$MODE"; return; fi
  if [ -f "$GAME_DIR/$WIN_EXE_REL" ]; then echo proton
  elif [ -x "$GAME_DIR/$NATIVE_BIN" ]; then echo native
  else echo unknown; fi
}
MODE="$(detect_mode)"
[ "$MODE" = unknown ] && die "Cannot find BL2 - neither $NATIVE_BIN nor $WIN_EXE_REL under $GAME_DIR"
if [ -z "$ISOLATION" ]; then ISOLATION=bwrap; fi   # device-masking works for both modes
GOLDBERG_SO="$BASE/goldberg/libsteam_api.so"    # native (classic Mr_Goldberg)
GOLDBERG_DLL="$BASE/goldberg/steam_api.dll"     # proton (gbe_fork)

# Goldberg emulator downloads (NOT committed to git - fetched by `fetch`). Pinned
# to known-good releases; override via env if these ever move.
GBE_FORK_TAG="${GBE_FORK_TAG:-release-2026_05_30}"
GBE_FORK_WIN_URL="${GBE_FORK_WIN_URL:-https://github.com/Detanup01/gbe_fork/releases/download/$GBE_FORK_TAG/emu-win-release.7z}"
CLASSIC_GOLDBERG_URL="${CLASSIC_GOLDBERG_URL:-https://gitlab.com/Mr_Goldberg/goldberg_emulator/uploads/2524331e488ec6399c396cf48bbe9903/Goldberg_Lan_Steam_Emu_v0.2.5.zip}"

resolve_pad() { local m; for m in $1; do [ -e "$m" ] && { readlink -f "$m"; return; }; done; }

# --------------------------------------------------------------- fetch deps -
# Download the Goldberg emulator binaries (kept out of git). Proton needs the
# gbe_fork Windows steam_api.dll; native needs the classic Mr_Goldberg Linux .so.
cmd_fetch() {  # downloads the Goldberg binary the detected MODE needs
  command -v bsdtar >/dev/null || die "bsdtar missing (sudo pacman -S libarchive)"
  command -v curl   >/dev/null || die "curl missing (sudo pacman -S curl)"
  mkdir -p "$BASE/goldberg"
  local tmp; tmp="$(mktemp -d)"; trap 'rm -rf "$tmp"' RETURN

  if [ "$MODE" = proton ]; then
    if [ -f "$GOLDBERG_DLL" ]; then ok "gbe_fork steam_api.dll already present"; return; fi
    say "Downloading gbe_fork (Windows) $GBE_FORK_TAG ..."
    curl -fsSL -o "$tmp/win.7z" "$GBE_FORK_WIN_URL" || die "download failed: $GBE_FORK_WIN_URL"
    bsdtar -xf "$tmp/win.7z" -C "$tmp" release/experimental/x86/steam_api.dll \
      || die "could not extract steam_api.dll from the archive"
    cp "$tmp/release/experimental/x86/steam_api.dll" "$GOLDBERG_DLL"
    file "$GOLDBERG_DLL" | grep -qi "PE32 .*i386" && ok "steam_api.dll (proton) fetched" \
      || die "fetched steam_api.dll is not the expected 32-bit PE"
  else
    if [ -f "$GOLDBERG_SO" ]; then ok "classic goldberg libsteam_api.so already present"; return; fi
    say "Downloading classic Mr_Goldberg (Linux) ..."
    curl -fsSL -o "$tmp/lin.zip" "$CLASSIC_GOLDBERG_URL" || die "download failed: $CLASSIC_GOLDBERG_URL"
    bsdtar -xf "$tmp/lin.zip" -C "$tmp" linux/x86/libsteam_api.so \
      || die "could not extract libsteam_api.so from the archive"
    cp "$tmp/linux/x86/libsteam_api.so" "$GOLDBERG_SO"
    file "$GOLDBERG_SO" | grep -q "ELF 32-bit" && ok "libsteam_api.so (native) fetched" \
      || die "fetched libsteam_api.so is not the expected 32-bit ELF"
  fi
}

# ------------------------------------------------------------------ check ---
cmd_check() {
  local fail=0
  say "== Mode: ${c_grn}$MODE${c_rst}  (isolation=$ISOLATION) =="
  say ""; say "== Prerequisites =="
  command -v qdbus6 >/dev/null && ok "qdbus6 (KWin tiling)" || warn "qdbus6 missing - auto-tiling disabled ${c_dim}(sudo pacman -S qt6-tools)${c_rst}"
  [ "$ISOLATION" = bwrap ] && { command -v bwrap >/dev/null && ok "bwrap" || { warn "bwrap missing"; fail=1; }; }
  if [ "$MODE" = proton ]; then
    command -v gamescope >/dev/null && ok "gamescope" || { warn "gamescope missing ${c_dim}(sudo pacman -S gamescope)${c_rst}"; fail=1; }
    command -v umu-run >/dev/null && ok "umu-run" || { warn "umu-run missing ${c_dim}(sudo pacman -S umu-launcher)${c_rst}"; fail=1; }
  else
    [ -f "$NATIVE_RUNTIME" ] && ok "Steam scout runtime" || { warn "scout runtime missing: $NATIVE_RUNTIME"; fail=1; }
    command -v strings >/dev/null && ok "strings (interface extraction)" || { warn "strings missing ${c_dim}(sudo pacman -S binutils)${c_rst}"; fail=1; }
  fi

  say ""; say "== Game =="
  if [ "$MODE" = native ]; then
    [ -x "$GAME_DIR/$NATIVE_BIN" ] && file "$GAME_DIR/$NATIVE_BIN" | grep -q ELF \
      && ok "native ELF: $NATIVE_BIN" || { warn "native binary missing"; fail=1; }
  else
    [ -f "$GAME_DIR/$WIN_EXE_REL" ] && ok "Borderlands2.exe" || { warn "exe missing: $WIN_EXE_REL"; fail=1; }
  fi

  say ""; say "== Goldberg =="
  if [ "$MODE" = native ]; then
    if [ -f "$GOLDBERG_SO" ] && file "$GOLDBERG_SO" | grep -q "ELF 32-bit"; then ok "libsteam_api.so (classic Mr_Goldberg, 32-bit ELF)"
    else warn "missing/invalid $GOLDBERG_SO (need classic Mr_Goldberg linux/x86 libsteam_api.so)"; fail=1; fi
  else
    if [ -f "$GOLDBERG_DLL" ] && file "$GOLDBERG_DLL" | grep -qi "PE32 .*i386"; then ok "steam_api.dll (PE32 i386)"
    else warn "missing/invalid $GOLDBERG_DLL (need Windows x86 gbe_fork experimental)"; fail=1; fi
  fi

  say ""; say "== Controllers =="
  local p1 p2 padfail=0; p1=$(resolve_pad "$P1_PAD_GLOB"); p2=$(resolve_pad "$P2_PAD_GLOB")
  [ -n "$p1" ] && ok "Player 1 pad -> $p1" || { warn "Player 1 pad not connected"; padfail=1; }
  [ -n "$p2" ] && ok "Player 2 pad -> $p2" || { warn "Player 2 pad not connected (turn it on)"; padfail=1; }
  # Controllers only matter for 'run'; setup passes REQUIRE_PADS=0.
  [ "${REQUIRE_PADS:-1}" = 1 ] && [ "$padfail" = 1 ] && fail=1

  say ""
  [ "$fail" = 0 ] && ok "All good - run:  ./bl2-splitscreen.sh setup" || warn "Fix the above, then re-run check."
  return $fail
}

# ------------------------------------------------------------------ setup ---
write_goldberg_settings() {  # $1=dir  $2=account  $3=steamid
  local ss="$1/steam_settings"; mkdir -p "$ss"
  printf '%s\n' "$APPID" > "$1/steam_appid.txt"
  cat > "$ss/configs.user.ini" <<EOF
[user::general]
account_name=$2
account_steamid=$3
language=english
ip_country=US
EOF
  printf '%s\n' "$2" > "$ss/account_name.txt"
  printf '%s\n' "$2" > "$ss/force_account_name.txt"   # classic goldberg name override
  printf '%s\n' "$3" > "$ss/force_steamid.txt"        # classic goldberg id override
  printf '%s\n' "$3" > "$ss/user_steam_id.txt"
  # Two same-host instances (each in its own Proton container) may not reach each
  # other via UDP broadcast, so co-op hangs at "Creating online session". Tell the
  # emu to send discovery directly to localhost so they always find each other.
  printf '127.0.0.1\n' > "$ss/custom_broadcasts.txt"
  # BL2 stalls on "Creating online session" waiting on (unreachable) online Steam
  # servers; offline mode makes the emu report Steam offline so it skips that wait
  # and goes to LAN. LAN co-op still works. Remove this file if it ever breaks join.
  cat > "$ss/configs.main.ini" <<EOF
[main::connectivity]
offline=1
EOF
}

# Old games hard-crash if the emu returns interfaces they don't expect. Extract
# the exact interface versions from the game's ORIGINAL Steam lib.
extract_interfaces() {  # $1=steam_settings dir  $2=path to original steam_api lib
  strings -n 5 "$2" 2>/dev/null | grep -E \
    '^(SteamClient|SteamGameServerStats|SteamGameServer|SteamUserStats|SteamUser|SteamFriends|SteamUtils|SteamMatchMakingServers|SteamMatchMaking|SteamRemoteStorage|SteamScreenshots|SteamHTTP|SteamController|SteamUGC|SteamAppList|SteamApps|SteamMusicRemote|SteamMusic|SteamHTMLSurface|SteamInventory|SteamVideo|SteamParentalSettings|SteamInput|SteamNetworkingUtils|SteamNetworkingSockets|SteamNetworkingMessages|SteamNetworking|SteamParties|STEAMAPPS|STEAMUSERSTATS|STEAMHTTP|STEAMSCREENSHOTS|STEAMUGC|STEAMREMOTESTORAGE|STEAMCONTROLLER|STEAMMUSIC|STEAMAPPLIST|STEAMUSER|STEAMFRIENDS|STEAMUTILS|STEAMNETWORKING)[A-Za-z0-9_]*[0-9]{3}$' \
    | sort -u > "$1/steam_interfaces.txt"
}

build_player() {  # $1=n  $2=account  $3=steamid
  local n="$1" acct="$2" sid="$3" pg="$BASE/p$1/game"
  say "  [$n] symlink game copy -> $pg"
  rm -rf "$BASE/p$n/game"; mkdir -p "$BASE/p$n/home"
  cp -as "$GAME_DIR/." "$pg/" || die "cp -as failed (need GNU coreutils)"
  if [ "$MODE" = native ]; then
    rm -f "$pg/libsteam_api.so"; cp "$GOLDBERG_SO" "$pg/libsteam_api.so"
    write_goldberg_settings "$pg" "$acct" "$sid"
    extract_interfaces "$pg/steam_settings" "$GAME_DIR/libsteam_api.so"
    [ -s "$pg/steam_settings/steam_interfaces.txt" ] || warn "  [$n] no interfaces extracted (game may crash)"
  else
    local w="$pg/Binaries/Win32"
    # Wine resolves a SYMLINKED exe to its target directory and loads DLLs from
    # THERE (the real steam_api.dll -> "Steam must be running"), bypassing our
    # Goldberg dll. Make the exes real copies so DLL search happens in our dir.
    local e real
    for e in Borderlands2.exe Launcher.exe; do
      [ -L "$w/$e" ] && { real=$(readlink -f "$w/$e"); cp --remove-destination "$real" "$w/$e"; }
    done
    # keep a copy of the original Windows lib before overwriting, for interfaces
    [ -f "$w/steam_api.dll.orig" ] || cp -L "$w/steam_api.dll" "$w/steam_api.dll.orig" 2>/dev/null
    write_goldberg_settings "$w" "$acct" "$sid"
    extract_interfaces "$w/steam_settings" "$w/steam_api.dll.orig"
    rm -f "$w/steam_api.dll"; cp "$GOLDBERG_DLL" "$w/steam_api.dll"
    mkdir -p "$BASE/p$n/prefix"
  fi
  ok "  [$n] account '$acct' (steamid $sid)"
}

cmd_setup() {
  cmd_fetch                                     # download Goldberg if not present
  REQUIRE_PADS=0 cmd_check || die "check failed - resolve the above before setup"
  say ""; say "== Building player copies ($MODE) =="
  build_player 1 "Player1" "76561197960287930"
  build_player 2 "Player2" "76561197960287931"
  say ""; ok "Setup complete.  Launch with:  ./bl2-splitscreen.sh run"
}

# -------------------------------------------------------------------- run ---
# Pin the game to windowed half-screen in its own config, so it doesn't apply a
# saved fullscreen mode after loading (which overrides -windowed and unstacks the
# tiling). Section-aware: ResX/Fullscreen appear in several sections.
patch_native_config() {  # $1=player home  $2=width  $3=height
  local f
  f=$(find "$1" -ipath "*willowgame/config/willowengine.ini" 2>/dev/null | head -1)
  [ -f "$f" ] || return 0
  # Config uses CRLF: strip trailing CR for matching, re-add it on output.
  awk -v W="$2" -v H="$3" '
    { cr = (sub(/\r$/,"") ? "\r" : "") }
    /^\[/ { sec=$0 }
    {
      l=$0
      if (sec=="[WinDrv.WindowsClient]") {
        if (l ~ /^StartupFullscreen=/)  l="StartupFullscreen=False"
        else if (l ~ /^StartupResolutionX=/) l="StartupResolutionX=" W
        else if (l ~ /^StartupResolutionY=/) l="StartupResolutionY=" H
      } else if (sec=="[SystemSettings]") {
        if (l ~ /^Fullscreen=/)          l="Fullscreen=False"
        else if (l ~ /^WindowedFullscreen=/) l="WindowedFullscreen=False"
        else if (l ~ /^ResX=/)           l="ResX=" W
        else if (l ~ /^ResY=/)           l="ResY=" H
      } else if (sec=="[FullScreenMovie]") {
        if (l ~ /^StartupMovies=/) next                 # drop the intro logos
        else if (l ~ /^bForceNoMovies=/) l="bForceNoMovies=TRUE"
      }
      printf "%s%s\n", l, cr
    }' "$f" > "$f.tmp" && mv "$f.tmp" "$f"
}

# Proton keeps its config inside the Wine prefix. We patch WillowEngine.ini to:
#  - drop the intro movies (straight to menu; resolution is set by -ResX/-ResY);
#  - always keep RUNNING when unfocused (bPauseOnLossOfFocus=FALSE) - split-screen
#    focuses only one window at a time, and the default TRUE freezes the unfocused
#    instance (its load stalls until you nudge the mouse);
#  - mute when unfocused (bMuteAudioWhenNotInFocus=TRUE) so audio follows the focused
#    window instead of every instance playing at once.
patch_proton_config() {  # $1 = prefix dir
  local f
  f=$(find "$1/drive_c/users" -ipath "*Borderlands 2*Config/WillowEngine.ini" 2>/dev/null | head -1)
  [ -f "$f" ] || return 0
  awk '
    { cr = (sub(/\r$/,"") ? "\r" : "") }
    /^\[/ { sec=$0 }
    { l=$0
      if (sec=="[FullScreenMovie]") { if (l ~ /^StartupMovies=/) next; else if (l ~ /^bForceNoMovies=/) l="bForceNoMovies=TRUE" }
      else if (sec=="[Engine.Engine]") {
        if (l ~ /^bPauseOnLossOfFocus=/)     l="bPauseOnLossOfFocus=FALSE"
        else if (l ~ /^bMuteAudioWhenNotInFocus=/) l="bMuteAudioWhenNotInFocus=TRUE"
      }
      printf "%s%s\n", l, cr }' "$f" > "$f.tmp" && mv "$f.tmp" "$f"
}

mask_other_pad_args() {  # bwrap args hiding every pad except kept node $1
  local keep="$1" node other g m
  for g in $P1_PAD_GLOB $P2_PAD_GLOB; do for m in $g; do
    [ -e "$m" ] || continue
    node=$(readlink -f "$m"); [ "$node" = "$keep" ] && continue
    printf -- '--bind /dev/null %s ' "$node"
    other="${m%-event-joystick}-joystick"
    [ -e "$other" ] && printf -- '--bind /dev/null %s ' "$(readlink -f "$other")"
  done; done
}

launch_player() {  # $1=n  $2=pad-node  $3=vidpid  -> sets LAUNCHED_PID
  local n="$1" pad="$2" vidpid="$3" pg="$BASE/p$1/game" wd
  local rw="${GW[$n]}" rh="${GH[$n]}"     # this player's render size
  local -a env cmd
  # Run under gamemode if installed: it flips the CPU to the performance governor
  # (system-wide) while playing, so instances load at full speed instead of stalling
  # on a power-saving governor until you jiggle the mouse. No-op if not installed.
  local -a gm=(); command -v gamemoderun >/dev/null && gm=(gamemoderun)
  # No gamescope in either mode: it doesn't pass raw controllers to nested clients,
  # so the game sees no pad. Run the game windowed and let KWin place it.
  if [ "$MODE" = native ]; then
    local home="$BASE/p$n/home"; wd="$pg"
    patch_native_config "$home" "$rw" "$rh"     # pin windowed size in the config
    env=( "HOME=$home" "XDG_DATA_HOME=$home/.local/share" "XDG_CONFIG_HOME=$home/.config"
          "LD_LIBRARY_PATH=$pg:${LD_LIBRARY_PATH:-}"
          "SteamAppId=$APPID" "SteamGameId=$APPID"
          "SDL_JOYSTICK_ALLOW_BACKGROUND_EVENTS=1" )
    cmd=( "${gm[@]}" "$NATIVE_RUNTIME" "./$NATIVE_BIN" -windowed "-ResX=$rw" "-ResY=$rh" )
  else
    wd="$pg/Binaries/Win32"
    patch_proton_config "$BASE/p$n/prefix"     # movies off, no focus-pause, mute-when-unfocused
    mkdir -p "$BASE/dxvk-cache"
    env=( "WINEPREFIX=$BASE/p$n/prefix" "GAMEID=0" "STORE=none"
          "UMU_RUNTIME_UPDATE=0"                # skip umu's startup update check
          # Shared D3D shader cache: the 2nd instance reuses shaders the 1st already
          # compiled instead of recompiling them while the 1st is using the GPU.
          "DXVK_STATE_CACHE_PATH=$BASE/dxvk-cache" )
    # Only use the SDL VID/PID filter in "sdl" mode. With bwrap masking it is
    # redundant AND can over-filter (it wrongly dropped the 360 pad), so skip it.
    [ "$ISOLATION" = sdl ] && env+=( "SDL_GAMECONTROLLER_IGNORE_DEVICES_EXCEPT=$vidpid" )
    [ -n "$PROTONPATH" ] && env+=( "PROTONPATH=$PROTONPATH" )
    cmd=( "${gm[@]}" umu-run "$pg/$WIN_EXE_REL" -windowed "-ResX=$rw" "-ResY=$rh" )
  fi

  # bwrap (if used) masks the other pad's /dev/input nodes for this instance.
  local -a inner
  if [ "$ISOLATION" = bwrap ]; then
    local -a maskargs=(); read -ra maskargs < <(mask_other_pad_args "$pad")
    inner=( bwrap --dev-bind / / --die-with-parent --chdir "$wd" "${maskargs[@]}" -- "${cmd[@]}" )
  else
    inner=( "${cmd[@]}" )
  fi

  say "${c_dim}[$n] pad=$pad  ${rw}x${rh} @ ${GX[$n]},${GY[$n]}  log=$BASE/p$n/log${c_rst}"
  # Background in the CURRENT shell (not a $() subshell) so the job is a real
  # child that cmd_run can wait on; hand the PID back via a global.
  ( cd "$wd" || exit 1; exec env "${env[@]}" "${inner[@]}" ) >"$BASE/p$n/log" 2>&1 &
  LAUNCHED_PID=$!
}

# --------------------------------------------------------- KDE/KWin tiling --
# One-shot: place each BL2 window on its half in LOGICAL coordinates. Run AFTER
# the splash movies so the game has settled at its configured size (tiling during
# the splash fights the game and looks wrong). All geometry is logical px.
cmd_tile() {
  command -v qdbus6 >/dev/null || { warn "qdbus6 not found - cannot auto-tile (drag windows manually)"; return 0; }
  # Left/right split, both windows vertically centered (WIN_Y).
  # Per-window geometry: window[0]=player1, window[1]=player2 (launch order).
  local js; js="$(mktemp --suffix=.js)"
  cat > "$js" <<EOF
(function(){
  var geo=[{x:${GX[1]},y:${GY[1]},w:${GW[1]},h:${GH[1]}},
           {x:${GX[2]},y:${GY[2]},w:${GW[2]},h:${GH[2]}}];
  var l=(workspace.windowList?workspace.windowList():workspace.clientList());
  var wins=l.filter(function(w){
    var s=((w.resourceClass||"")+" "+(w.resourceName||"")+" "+(w.caption||"")).toLowerCase();
    return s.indexOf("borderlands")>=0 || s.indexOf("steam_app")>=0;
  });
  wins.sort(function(a,b){ return (""+a.internalId)<(""+b.internalId)?-1:1; });
  for(var i=0;i<wins.length && i<2;i++){
    var w=wins[i], g=geo[i];
    try{w.fullScreen=false;}catch(e){}
    try{w.setMaximize(false,false);}catch(e){}
    try{w.noBorder=true;}catch(e){}
    w.frameGeometry={x:g.x,y:g.y,width:g.w,height:g.h};
  }
})();
EOF
  qdbus6 org.kde.KWin /Scripting org.kde.kwin.Scripting.loadScript "$js" bl2tile >/dev/null 2>&1
  qdbus6 org.kde.KWin /Scripting org.kde.kwin.Scripting.start >/dev/null 2>&1
  qdbus6 org.kde.KWin /Scripting org.kde.kwin.Scripting.unloadScript bl2tile >/dev/null 2>&1
  rm -f "$js"
  ok "Placed windows (${DISPLAY_MODE}: ${GW[1]}x${GH[1]} + ${GW[2]}x${GH[2]})."
}

cmd_run() {
  [ -d "$BASE/p1/game" ] && [ -d "$BASE/p2/game" ] || die "run setup first"
  local p1 p2; p1=$(resolve_pad "$P1_PAD_GLOB"); p2=$(resolve_pad "$P2_PAD_GLOB")
  [ -n "$p1" ] || die "Player 1 controller not connected"
  [ -n "$p2" ] || die "Player 2 controller not connected (turn it on)"

  # Steam Input (active while Steam runs) injects VIRTUAL gamepads that SDL grabs
  # instead of the real pads, which defeats per-instance controller isolation.
  # Goldberg replaces Steam, so it isn't needed while playing.
  if pgrep -x steam >/dev/null; then
    warn "Steam is running - Steam Input's virtual gamepads can break per-player"
    warn "controller isolation. If a pad drives the wrong window, QUIT STEAM"
    warn "(Goldberg replaces it). Continuing in 5s..."
    sleep 5
  fi

  say "== Launching Borderlands 2 (mode=$MODE, isolation=$ISOLATION, display=$DISPLAY_MODE) =="
  say "${c_dim}P1 ${GW[1]}x${GH[1]}@${GX[1]},${GY[1]}   P2 ${GW[2]}x${GH[2]}@${GX[2]},${GY[2]}${c_rst}"
  local pid1 pid2
  launch_player 1 "$p1" "$P1_VIDPID"; pid1=$LAUNCHED_PID
  [ "$STAGGER" -gt 0 ] 2>/dev/null && sleep "$STAGGER"
  launch_player 2 "$p2" "$P2_VIDPID"; pid2=$LAUNCHED_PID

  local where="THEIR MONITORS"; [ "$DISPLAY_MODE" = split ] && where="THEIR HALVES"
  banner "WIGGLE YOUR MOUSE NOW -- KEEP IT MOVING" \
         "UNTIL BOTH GAMES REACH THE MAIN MENU." \
         "" \
         "DO NOT TOUCH THE WINDOWS: I WILL MOVE THEM" \
         "ONTO $where IN $SPLASH_WAIT SECONDS."

  # Move windows AFTER the splash - the game resizes itself during it, so tiling too
  # early makes the window flicker. Fire a few times so both settle.
  ( sleep "$SPLASH_WAIT"; cmd_tile >/dev/null 2>&1
    sleep 8; cmd_tile >/dev/null 2>&1
    sleep 12; cmd_tile >/dev/null 2>&1 ) &

  ok "Both instances launching (pids $pid1 / $pid2)."
  say "In-game: ${c_grn}Player 1${c_rst} → Play → host over LAN.  ${c_grn}Player 2${c_rst} → Play → Join → pick the LAN game."
  say "${c_dim}Re-place windows any time with:  ./bl2-splitscreen.sh tile${c_rst}"
  say "Press Ctrl-C to kill both instances."
  # Killing $pid1/$pid2 only hits the top of each tree; the game runs deeper inside
  # umu/pressure-vessel and survives. kill_instances tears down the whole tree.
  trap 'echo; kill_instances; exit 130' INT TERM
  wait "$pid1" "$pid2"
}

# ------------------------------------------------------------------ kill ----
# Terminate every Borderlands 2 process we launched (game exe + umu/Proton/Wine
# tree for our prefixes), SIGTERM first then SIGKILL. Scoped to our BASE dir so it
# won't touch unrelated Wine apps.
kill_instances() {
  local sig
  for sig in TERM KILL; do
    pkill -"$sig" -f 'Borderlands2\.exe'   2>/dev/null   # proton game
    pkill -"$sig" -x 'Borderlands2'        2>/dev/null   # native game
    pkill -"$sig" -f "$BASE/p[12]/"        2>/dev/null   # umu/proton/wine for our copies+prefixes
    [ "$sig" = TERM ] && sleep 2
  done
}

cmd_kill() {
  # Match the process NAME (comm) as a substring, not the full cmdline - otherwise
  # helper shells that merely have the game path in their args get counted. This
  # matches "Borderlands2.ex" (Proton, 15-char truncated) and "Borderlands2".
  pgrep 'Borderlands2' >/dev/null || { ok "No Borderlands 2 instances running."; return 0; }
  say "Killing Borderlands 2 instances..."
  kill_instances
  # pgrep -c prints "0" and exits non-zero on no match, so DON'T add `|| echo 0`
  # (that would double it). Command substitution keeps the "0" regardless of exit.
  local left; left=$(pgrep -c 'Borderlands2' 2>/dev/null); left=${left:-0}
  [ "$left" = 0 ] && ok "All instances killed." || warn "$left process(es) still lingering."
}

# ------------------------------------------------------------------ clean ---
cmd_clean() { cmd_kill; say "Removing generated copies/saves (real game untouched)..."; rm -rf "$BASE/p1" "$BASE/p2"; ok "Done."; }

case "${1:-}" in
  fetch) cmd_fetch ;;
  check) cmd_check ;;
  setup) cmd_setup ;;
  run)   cmd_run ;;
  tile)  cmd_tile ;;
  kill)  cmd_kill ;;
  clean) cmd_clean ;;
  *) say "Usage: $0 {fetch|check|setup|run|tile|kill|clean}   (MODE=native|proton to force)"; exit 1 ;;
esac