coopchat.lua

Status: new, built on already-confirmed pieces. Every individual mechanism here — the hijacked-NetEventCallback pattern, the below-8 event ID constraint, UI.Chat’s Shift-aware typing — is independently confirmed elsewhere on this wiki (see the citations throughout below). This specific combined script hasn’t yet accumulated its own separate live-test history.

The current, improved implementation of A Basic Co-op Text Chat — see that deep dive’s Update section for exactly how this replaces the original approach and which of its limitations this closes.

What it does

A co-op text chat window bound to a toggle key (F2 by default): press it to open a typed-input line on a UI.Chat window, type a message, Enter sends it to the other player over the network, Esc cancels. Received messages appear in the same scrolling log, titled by sender (P1/P2).

Setup

uilib.lua loaded first, on both machines (OnLoad).
Copy this file to scripts/OnKey/coopchat.lua on both machines, and add coopchat.lua=f2 under [OnKey].
Press F2 to open the input line. Type, Enter sends, Esc cancels.

local KEYVAL = "f2" is deliberately the very first line — the loader only picks up a script’s default hotkey by reading its first 10 lines, so a KEYVAL declaration sitting any later than that (as in an earlier draft of this file, past a long header comment) is silently never found, and the key falls back to needing an explicit lua_loader.ini entry instead of just working out of the box.

How the pieces fit

Front end: one UI.Chat window supplies the entire display + typed-input side — scrolling log, Shift-aware character input, focus handling. Nothing here reimplements any of that.
Transport: Net.SendCustomEvent("MrxFactionManager", EV_CHAT, ...) — the identical hijacked-NetEventCallback mechanism, always-resident target, and below-8 event ID constraint the networking deep dive and the original coop-chat deep dive both establish. EV_CHAT = 5, chosen (per the source comment) to avoid MrxFactionManager’s own real event IDs (0/1/2).
Encoding: Net.SendCustomEvent can’t carry a raw string — only numbers survive the trip intact (see coop-chat’s Send section for why). packBytes/unpackBytes pack 3 characters per numeric argument (24-bit-safe: byte1*65536 + byte2*256 + byte3), instead of the original approach’s one character per argument slot.
Chunking: SLOTS = 5 (matching the largest array size confirmed safe anywhere in the decompiled corpus), of which the first two are a packed header (message id + chunk sequence + chunk total, all three packed into one number the same way packBytes packs characters) and a sender id, leaving 3 payload slots — 9 characters — per call. A message longer than that is split across multiple sequential SendCustomEvent calls and reassembled on the receiving end keyed by sender*256 + msgId, so out-of-order or partially-arrived chunks resolve correctly once every piece has shown up.
Sender identity: localId() tries Player.GetLocalPlayerId, then Player.GetLocalId, then falls back to a Net.IsServer() guess (server = 0, client = 1) if neither exists — sent in slot 2, decoded to "P1"/"P2" on receipt.
Movement freeze: Player.SetInputEnabled — the same native control gate the briefing/state-machine code uses — wraps UI.Chat’s prompt()/_endInput(), so the player can’t move or fire while composing a message. Confirmed (per the source comment) not to block lua-bridge’s own key capture, which sits below the game’s own input-enabled flag entirely.
Local echo retitling: UI.Chat:push() already shows what you type as a bare line the moment you submit it (via the input prompt’s own echo); onSubmit removes that bare line and re-pushes it prefixed with your own "P<id>:" label, so your own sent messages look consistent with received ones instead of the only unlabeled line in the log.

The full script

local KEYVAL = "f2"   -- must be in the first 10 lines (toggle key; add "coopchat.lua=f2" under [OnKey])

-- coopchat.lua --------------------------------------------------------------
-- Co-op text chat: a UI.Chat window (uilib) + the pack/chunk encoding that
-- carries arbitrary text over Net.SendCustomEvent (past the string->hash wall).
--
-- UI.Chat supplies the whole front end (scrolling log + Shift-aware typed input);
-- we supply encode/decode, P1/P2 sender titling, and a movement freeze while
-- typing (Player.SetInputEnabled -- the game's own control gate, same call the
-- briefing/state code uses; it does NOT block the lua-bridge key capture).
--
-- DEPLOY (both machines): uilib.lua loaded first (OnLoad). Then copy this to
-- <game>\scripts\OnKey\coopchat.lua and add  coopchat.lua=f2  under [OnKey].
-- Press F2 to open the input line; type, Enter sends, Esc cancels.
----------------------------------------------------------------------------

if not (_G.UI and UI.Chat) then
  if Loader and Loader.Printf then Loader.Printf("[coopchat] load uilib.lua first (press its key)") end
  return
end
import("MrxFactionManager")   -- always-resident hijack target

-- ===== wire constants (bump SLOTS to just under the coopchat_test CAP result) =====
local EV_CHAT       = 5     -- <8 event-id; avoids MrxFactionManager's own 0/1/2
local BYTES_PER_NUM = 3     -- 24-bit float-safe
local SLOTS         = 5     -- slot1=header, slot2=senderId, rest=payload
local PAY_SLOTS     = SLOTS - 2
local CHARS_PER_SEND = PAY_SLOTS * BYTES_PER_NUM

local function try(f, ...) if type(f) == "function" then local ok, v = pcall(f, ...); if ok then return v end end end
local function packBytes(s, i)
  return (string.byte(s, i)   or 0) * 65536
       + (string.byte(s, i+1) or 0) * 256
       + (string.byte(s, i+2) or 0)
end
local function unpackBytes(n, out)
  local b1 = math.floor(n/65536) % 256
  local b2 = math.floor(n/256)   % 256
  local b3 = n % 256
  if b1 > 0 then out[#out+1] = string.char(b1) end
  if b2 > 0 then out[#out+1] = string.char(b2) end
  if b3 > 0 then out[#out+1] = string.char(b3) end
end
local function localId()
  return try(Player and Player.GetLocalPlayerId)
      or try(Player and Player.GetLocalId)
      or ((Net and Net.IsServer and Net.IsServer()) and 0 or 1)
end
local function label(id) return "P" .. (tonumber(id or 0) + 1) end   -- id 0/1 -> P1/P2

-- freeze/unfreeze the local player's movement (game control gate; leaves chat input intact)
local function setMove(on)
  local p = try(Player and Player.GetLocalPlayer)
  if p and Player.SetInputEnabled then pcall(Player.SetInputEnabled, p, on) end
end

local function nextMsgId() _G.__cc_mid = ((_G.__cc_mid or 0) + 1) % 255; return _G.__cc_mid end

local function SendChat(text)
  if not (Net and Net.SendCustomEvent) then return end
  local me    = localId()
  local total = math.max(1, math.ceil(string.len(text) / CHARS_PER_SEND))
  local mid   = nextMsgId()
  for c = 0, total - 1 do
    local a = { mid * 65536 + c * 256 + total, me }
    local base = c * CHARS_PER_SEND
    for p = 0, PAY_SLOTS - 1 do
      local bi = base + p * BYTES_PER_NUM + 1
      if bi <= string.len(text) then a[#a + 1] = packBytes(text, bi) end
    end
    Net.SendCustomEvent("MrxFactionManager", EV_CHAT, a, true)
  end
end

-- onSubmit: send, then retitle prompt's bare local echo to "P<me>: text"
local function onSubmit(text)
  SendChat(text)
  if _G.COOPCHAT and _G.COOPCHAT.ui then
    local ui = _G.COOPCHAT.ui
    local wrap = UI.wrap and UI.wrap(text, 52)
    if type(wrap) == "table" and ui._log then
      for _ = 1, #wrap do table.remove(ui._log) end   -- drop the bare lines prompt just pushed
      ui:push(label(localId()) .. ": " .. text)        -- re-push titled
    end
  end
end

-- ===== build once: the UI.Chat window + the receiver hijack + movement wraps =====
if not _G.COOPCHAT then
  _G.COOPCHAT = {}
  local C = _G.COOPCHAT
  C.ui = UI.Chat{ x = 20, y = 330, w = 384, title = "CO-OP CHAT", onSubmit = onSubmit }

  -- wrap prompt()/_endInput() to freeze movement only while the input line is open
  local basePrompt, baseEnd = C.ui.prompt, C.ui._endInput
  C.ui.prompt   = function(self, cb) setMove(false); return basePrompt(self, cb) end
  C.ui._endInput = function(self)     setMove(true);  return baseEnd(self)      end

  -- receiver: decode + reassemble chunks, then push the titled line
  local orig = MrxFactionManager.NetEventCallback
  local rx = {}   -- rx[sender*256+msgId] = { total=, parts={[seq]=str} }
  MrxFactionManager.NetEventCallback = function(evt, tArgs)
    if evt == EV_CHAT then
      local h      = tArgs[1] or 0
      local msgId  = math.floor(h/65536) % 256
      local seq    = math.floor(h/256)   % 256
      local total  = h % 256
      local sender = tArgs[2] or 0
      local buf = {}; local i = 3; while tArgs[i] ~= nil do unpackBytes(tArgs[i], buf); i = i + 1 end
      local key = sender * 256 + msgId
      local m = rx[key]; if not m then m = { total = total, parts = {} }; rx[key] = m end
      m.parts[seq] = table.concat(buf)
      local have = 0; for _ in pairs(m.parts) do have = have + 1 end
      if have >= m.total then
        local o = {}; for cc = 0, m.total - 1 do o[#o + 1] = m.parts[cc] or "" end
        rx[key] = nil
        C.ui:push(label(sender) .. ": " .. table.concat(o))
      end
    elseif orig then
      orig(evt, tArgs)
    end
  end

  C.ui:push("[co-op chat ready -- press " .. KEYVAL .. " to type]")
  Loader.Printf("[coopchat] built (UI.Chat + receiver + movement freeze)")
end

-- ===== each keypress: (re)bind send so file edits apply, then open the input line =====
_G.COOPCHAT.ui:prompt(onSubmit)

coopchat.lua

What it does

Setup

How the pieces fit

The full script

See also