BT411/docs/GLASS_COCKPIT.md

# GLASS_COCKPIT — running ledger (desktop developer layer)

Detailed running log for the `glass-cockpit` branch work: PadRIO, on-screen panel/plasma,
miniconsole, Steam transport/lobby. Curated digest: `context/glass-cockpit.md` (read that
first); this file carries the step-by-step detail, evidence, and verification transcripts.

---

## 2026-07-17 — Step 1: branch + compile gates + scaffolding

- Branch `glass-cockpit` created from master @ `e2c21c4`.
- `CMakeLists.txt`: `option(BT_GLASS OFF)` + `option(BT_STEAM OFF)`; `BT_STEAM` without
  `BT_GLASS` is a configure-time FATAL_ERROR; gates append to `BT_DEFS` (flows to all three
  targets); `STATUS` line prints gate state at configure. Gated `target_sources` blocks will be
  added per-TU as they land (CMake would reject nonexistent source files now).
- `.gitignore`: `build-pod/`, `build-steam/`, `content/bindings.txt`, `content/frontend.egg`,
  `content/steam_appid.txt`.
- Verification (this step): defaults configure prints `BT_GLASS=OFF BT_STEAM=OFF` and builds
  (purity build); `-DBT_GLASS=ON` and ON/ON configures print correct gate state; the
  BT_STEAM-without-BT_GLASS negative test FATAL_ERRORs. Full 3-config BUILD matrix becomes
  meaningful from step 2 (first gated code) and is re-run there.

## 2026-07-17 — Step 2a: the .CTL positional-attribute off-by-one — CONFIRMED and FIXED (ungated)

**The bug [T2, live-verified]:** the streamed `.CTL` "L4" mapping resource carries the 1995
binary's positional attribute ids (stick=3, throttle=4, ...), resolved at install time by
`Simulation::GetAttributePointer(id)` → `AttributeIndexSet::Find(id)` = `attributeIndex[id-1]`
(positional). `MechControlsMapper` chained its enum on `Subsystem::NextAttributeID == 2`, but
the binary's chain reaches 3 (one base attribute we don't publish) — so EVERY streamed mapper
record landed one member late.

**Evidence (new `BT_CTRLMAP_LOG=1` diagnostic in `LBE4ControlsManager::CreateStreamedMappings`,
`engine/MUNGA_L4/L4CTRL.cpp` — permanent, env-gated, default off).** Before the fix
(`build-pod` Debug, `-egg DEV.EGG`, dev platform):
```
rec 0  subsys 0 group 1(Joy)    elem 0  attrID 3 -> +0xe4   (= throttlePosition: WRONG, stick intended)
rec 1  subsys 0 group 0(Scalar) elem 0  attrID 4 -> +0xe8   (= pedalsPosition:   WRONG, throttle intended)
rec 2  subsys 0 group 3(Button) elem 63 attrID 6 -> +0xf0   (= speedDemand:      WRONG, reverse intended)
rec 4-6 attrID 10/11/12 -> lookRight/lookBehind/lookDown    (one late; LookLeft/Right/Behind intended)
```
Spacing attr3→attr4 was 4 bytes (Scalar) where stick→throttle must be 8 (ControlsJoystick).
The weapons chain (attrID 19 → +0x31c TriggerState) was already correct — mechweap was
pad-aligned in task #16 (gotcha #11). Torso (subsys 17) also aligned (MechSubsystem publishes
binary id 2). ONLY the mapper chain (subsys 0) was off. On the dev box the keyboard INPUT
BRIDGE (writes the mapper members directly, after the engine push) masked it; on a REAL POD the
serial RIO throttle scalar would have driven `pedalsPosition` and the stick x/y would have
driven throttle+pedals — the Phase-8 landmine prior art predicted.

**The fix (ungated, pod-correctness — user-approved 2026-07-17):** `mechmppr.hpp` pins the enum
to the binary numbering (`MechControlsMapperPadFirstAttributeID = 2`, stick=3 ... PilotArray=
0x16); `mechmppr.cpp` pads id 2 with a valid never-bound entry (the mech.cpp attrPad idiom) and
locks the base + pinned ids with `static_assert`s. `L4MechControlsMapper::TargetRangeExponent`
(chained) moves 0x16→0x17, matching the binary's own arithmetic; it is bound by name (audio
zoom-blip), so no consumer shifts.

**After the fix:** `attrID 3 -> +0xdc` (stick), `attrID 4 -> +0xe4` (throttle, 8-byte spacing
✓), `attrID 6 -> +0xec` (reverse), `10/11/12 -> +0xfc/+0x100/+0x104` (the look trio); torso +
weapons unchanged. Regression: headless forced-walk run (`BT_FORCE_THROTTLE=1`) drives normally
— `[mppr] thr=1 -> speedDemand=61.501`, gait cycles, position advances, 31/31 subsystems
simulated, no faults.

## 2026-07-17 — Steps 2b-2e: PadRIO, stand-downs, displays, preset — DONE + verified

**2b (RIOBase + PadRIO, commit ac57a47):** `L4RIO.h` splits abstract `RIOBase` (enums, the five
analog Scalars, pure `GetNextEvent`/`SetLamp`, no-op serial ops, NEW `IsOperational()`) out of
serial `RIO` (`: PCSerialPacket, RIOBase` — ctor assigns as before, zero behavioral delta);
`L4CTRL.h` `rioPointer` retyped `RIOBase*`; gated `L4CONTROLS=PAD` factory arm. NEW gated TUs
`L4PADRIO.*` (XInput+keyboard → the surface; 3s hot-plug; focus-guarded keys; per-poll
AnalogEvent heartbeat time-gated so the manager's drain loop terminates; `lampState[]`;
static `SetScreenButton` — button addresses AND the keypad space 0x50-0x6F → KeyEvents) and
`L4PADBINDINGS.*` (`content\bindings.txt`, default written on first run; deflect/slew/set axis
model; addresses validated vs ButtonCount).

**2c (stand-downs, commit 9f35a80):** engine query `BTRIODevicePresent()` (ungated —
pod-correct); both dev bridges (`mech4.cpp` attr writes, `mechmppr.cpp` BT_KEY_BRIDGE) gate
their WRITES: unset=auto / "0"=off / else on; forced harness always rides. **Definitive live
test:** OS-injected LSHIFT hold slewed PadRIO throttle 0→0.33→1.0 with `pre==thr` every frame —
the value arrives via the ENGINE push through the streamed `.CTL` binding (bridge stood down),
`speedDemand=61.501` from authentic InterpretControls.

**2d/2e (displays + preset, commits db9ac94 + 418acf0):** the on-screen panel follows **vRIO**
(`C:\VWE\vrio` — `CockpitLayout.cs`/`PanelCanvas.cs`, per Cyd): five 4x2 MFD clusters
(descending addresses), Throttle/Secondary/Screen/Joystick 1x8 columns, two 4x4 hex keypads
(0x50 internal→pilot unit, 0x60 external→operator unit), physical names, red/yellow/blue
coloration, 500/250/125ms flash, right-click latch — 104 controls. `PlasmaWindow :
Video8BitBuffered` renders the 128x32 plasma via the SAME gauge-renderer path as serial
(buffer is TOP-DOWN — the flip rendered it upside down, user-reported + fixed). MFD surfaces =
the EXISTING dev-gauge modes (no new code, no L4VB16 exposure). `-platform glass` preset +
run.cmd token. **Button-trap guard (e2c21c4 pattern):** the authentic base
`ConfigureMappableMessageHandler` FAIL trap is `abort()` under DEBUGOFF — any aux/zoom button
without its reconstructed L4 override KILLED the game on press (panel makes all reachable).
Default now log+ignore; `BT_BUTTON_TRAP=1` restores the hard trap. Verified: synthetic panel
click → 2 `[FAIL]` (press+release through panel→PadRIO→ProcessRIOEvent→streamed mapping), game
survives. NOTE: each `[FAIL]` marks a missing L4 override — reconstruction backlog, see
[[open-questions]].

**Step-2 verification matrix (all passed 2026-07-17):**
1. Purity: defaults `build-pod/` compiles (known mech3 /FORCE externals only); seam audit —
   `BT_GLASS`/`BT_STEAM` mentions ONLY in CMakeLists, btl4main.cpp preset region, L4CTRL.cpp
   (include+PAD arm), L4GREND.cpp (include+SCREEN branch), gated TUs, run.cmd docs.
2. Pod solo forced-walk clean (§2a).
3. **2-node loopback MP on the pod build:** A `-egg MP.EGG -net 1501` + B `-net 1601` +
   `btconsole.py` relay — both nodes launch into the running mission (77/76 ticks, mechs at
   their drop zones, gait/target loops live).
4. Glass build: PadRIO drives through the authentic mapper path; panel click path live; plasma
   window; all boot lines present.
Deferred to the user (visual-only): panel/plasma appearance vs vRIO on screen, XInput stick
feel, `L4PADFLIP` polarity.

## 2026-07-17 — Step 3: the miniconsole — DONE + verified (commit c4ca87b)

**Architecture: the console stays a wire peer.** `game/glass/btl4fe.*` (GDI catalog menu + the
console-shape egg writer) and `btl4console.*` (the LocalConsole marshal: a worker-thread console
CLIENT speaking the `tools/btconsole.py` protocol verbatim — 1040-byte chunked
`ReceiveEggFileMessage`, 20s settle, `RunMission`×2, stay connected, own the clock,
`StopMission`(id 6)@expiry; logs `content\marshal.log`). The engine runs the 100% stock console
ladder — ZERO engine hooks; the planned `L4APP.H` setters proved unnecessary (launches pass real
argv on relaunch). WinMain: one gated block — zero-mission-arg glass launch → menu → relaunch
self with mission argv (`BT_FE_EGG/PODS/SECS` arm the marshal; `BT_FE_LOOP` returns exits to the
menu; menu relaunches CLEAR the handoff — the leak re-armed a marshal in cycle test 1).

**Verified (synthetic menu drives, all autonomous):**
- Golden egg: `frontend.egg` section sequence + line offsets IDENTICAL to `MP.EGG`; ordinal
  pages verbatim; GDI name-glyph pages in MP.EGG framing (32/8 rows, 16 bytes/line).
- Solo cycle: menu → egg → relaunch → marshal → stock ladder → mission RUNS (58+ ticks) → 60s
  clock → stop → menu returns with clean env.
- **HOST LAN 2-node:** peer started manually (`-net 1601`); menu-hosted launch → marshal feeds
  BOTH pods (2-pilot egg, 10 chunks each) → both in-mission (65/18 ticks) → stop both → host
  returns to the menu, peer idles at console-wait.

## 2026-07-17 — Step 4 pre: Steamworks SDK 1.64 vendored (commit 23c0019)

Official Valve zip (provided by Cyd at the repo root), extracted to
`extern/steamworks_sdk_164/` and trimmed to `public/` + `redistributable_bin/` + Readme
(12.5 MB); zip removed. Consumed only under `-DBT_STEAM=ON`.

## 2026-07-17/18 — Step 4: the Steam wire — CODE COMPLETE (commits e79e8fa, 48ede2f, f703bb1)

**4a (e79e8fa) — the wire seam:** file-local `BTNetSend/Recv/Accept/Close` wrappers around the
9 raw Winsock sites in `L4NET.CPP`; OFF builds are pure code motion. Regression: 2-node loopback
MP through the seam — mesh forms, full 31/31 mission on both nodes.

**4b (48ede2f) — the transport:** gated TU `L4STEAMNET` — pseudo-SOCKETs (0x5EA0xxxx) behind the
seam; the engine's TCP byte stream rides reliable-NoNagle Steam messages re-assembled into
per-connection rings (recv semantics preserved: empty→WSAEWOULDBLOCK, closed→0); seam
completions: `CheckSocket` (peer = token address), `OpenConnection` TCP_OPEN delegate,
`GetMyAddress` self-token. Install on `BT_STEAM_NET=1`; graceful degrade to Winsock at every
step. BOTH pumps needed (`SteamAPI_RunCallbacks` + sockets `RunCallbacks`).

**4c (f703bb1) — the lobby + THE FAKEIP LESSON [T2]:** prior art assumed FakeIP survives the
per-mission process relaunch — DISPROVEN live (menu process got 169.254.124.110, the mission
process got 169.254.54.234; the pod timed out connecting to its own stale address). Redesign:
roster addresses are opaque ipv4-shaped TOKENS (`169.254.77.N`, ports 1501 console / 1502 game)
minted by the host at GO and mapped to Steam IDENTITIES; connections ride
`ConnectP2P(identity, channel)` (console=0, game=1); the map hands off via env
(`BT_FE_MYFAKE`/`BT_FE_STEAMMAP`). `btl4lobby`: ISteamMatchmaking room (`btl4=1` filter),
pilots publish name/mech/color, host GO mints tokens + writes `btl4map` + `btl4go`.

**Verified single-machine (ON/ON, live Steam client):** menu → HOST STEAM LOBBY → room → GO →
map `169.254.77.1=<steamID64>` → egg roster carries the token → mission process
`[steamnet] up ... 1 roster token(s) incl. self` → pod self-matches → stock console ladder →
mission RUNS (46 ticks). 3-config build matrix green throughout. **Remaining (user hardware):**
the live 2-account cross-machine session — procedure in `docs/STEAM_TEST.md`.

## 2026-07-20 — Glass input-coverage audit + keyboard reconciliation

**Trigger:** making BT_GLASS the permanent player experience — familiar desktop keys dead, "most
panel buttons do nothing". Full audit of every input surface (bindings.txt keys, the 72-button
panel, the streamed .CTL EventMapping records, the typed 1995 channel), then the fix set.

### Finding 1 — THE panel-dead-buttons root cause: MechRIOMapper message ids shifted [T1→T2 fixed]
`MechRIOMapper`'s enum chained `Aux1QuadMessageID = L4MechControlsMapper::NextMessageID` (=0x19),
registering all 18 RIO handlers at ids 0x19-0x2a. The binary RIO table @0051dd30 RE-REGISTERS the
base aux/zoom ids **3..0x13** with the override handlers (Hotbox = 0x1a @0051de98) — that
re-registration over the base FAIL-trap ids is the whole point of the derived table. Streamed
`.CTL` events carry the binary ids, so every MFD-bank/zoom press found only the base
`ConfigureMappableMessageHandler` → `[FAIL]` (26 of 72 panel buttons dead; on a real pod with the
hard trap, an abort()). Hotbox worked by accident (sender + entry both used the same wrong 0x2a).
Fixed: ids pinned to the binary numbering + static_assert locks (`btl4mppr.hpp`). Verified live:
panel 0x0F/0x08/0x27/0x20 → `[mode] preset` lines, 0x10/0x11 zoom no longer FAIL. (Residual
fidelity gap: the binary RIO table also carries its OWN Keypress id 0x19 → @004d2514,
unreconstructed; we still register the shared L4 Keypress 0x17 — works, logged in the backlog.)

### Finding 2 — the always-active msg-4 records IDENTIFIED [T1] (closes the #9 open question)
Binary message tables decoded from section_dump (16-byte {id,name,fn,0} entries): per-receiver-
class id spaces. Roster (ARENA1 MadCat): subs 3=Reservoir, 4-9=Condenser1-6, 10-13=GeneratorA-D.
So: **0x2C = the COOLANT FLUSH button** (Reservoir InjectCoolant, WORKS), **0x2F/0x2E/0x2D/0x2B/
0x2A/0x29 = per-condenser VALVE buttons** (MoveValve, WORK), **0x1A-0x1D = Generator A-D ON/OFF**
(`ToggleGeneratorOnOff` id 4, table @0050fb90 fn @004b1ed0 — DEAD, unreconstructed). Also new:
0x13 → Mech **DuckRequest** (0x1a @0049fa00 — the manual's CROUCH button!), 0x28 → Mech
**BalanceCoolant** (0x16 @0049f728), 0x12 → ThermalSight toggle (id 3), 0x14 → Searchlight +
Searchlight2 **ToggleLamp** (id 3 @004b860c — body reconstructed but `Searchlight::
MessageHandlers` is default-constructed EMPTY, so it never fires: the quick win). Weapon
Eng-page extras: msg 0x3 = **ToggleCooling** (HeatableSubsystem @0050e41c fn @004ad6f8, unwired),
msg 0xb = **ToggleSeekVoltage** (energy @004ba478) / **EjectAmmo** (ammo weapons @004bb9b8),
Myomers msg 9 = ToggleSeekVoltage (@004b8a48; body exists, unwired). Unhandled messages are
SILENT (Receiver::Receive ignores an unfound id) — the dead-button census cannot come from
[FAIL] logs alone; it comes from the BT_CTRLMAP_LOG record dump × the handler tables.

### Finding 3 — glass keyboard: stand-down + double dispatch [T2]
ALL btinput actions (drive keys, M/N/J/K/L/H/C/V/B/G/F5-F9) stand down when PadRIO owns the path
— nothing on the game side polls keys directly (BTInputPoll is the only GetAsyncKeyState
consumer). Meanwhile the typed 1995 channel stays LIVE (glass preset = `PAD,KEYBOARD`) with NO
suppression — so Cyd's old bindings double-dispatched: W (keypad row) also typed 'w' = pilot
select 0; C (fire middle) also typed 'c' = MFD3 Eng3; NUMPAD key-UPS alias to letter hotkeys
(VK_NUMPAD2=0x62='b' = MFD3 Quad, VK_F5=0x74='t' = pilot select 3). This is the historic
pre-btinput double-dispatch, back on the glass side.

### The fix set (landed)
1. `btl4mppr.hpp` — RIO id pinning (ungated, pod-correctness; the step-2a idiom).
2. `L4PADRIO.*` — typed-channel suppression tables built from the loaded bindings (+hardcoded
   keys), `PadRIO::SuppressKey` consumed by a `#ifdef BT_GLASS` arm next to the btinput hook in
   `L4CTRL.cpp:1506` block; V joins backtick on the view-toggle edge; J/K/L fire
   `gBTPresetCycle[3]` (the same seam the dev poll feeds — no binary analog exists for a "cycle"
   button; the body is the authentic SetPresetMode).
3. `L4PADBINDINGS.cpp` + `content\bindings.txt` — the MERGED default map (user decision:
   keyboard = the ~20 core gameplay actions on the CONTROLS.MAP keys; the PANEL covers all 72
   pod buttons by click/latch). W/S throttle, A/D pedals, Q/E twist, R/F elevation, X all-stop,
   1-4/Space/Ctrl fire + LALT reverse + B look-behind, M=0x18, N=0x15, H=0x2C (flush hold),
   C=0x2F (Condenser1 valve), G=0x0E (weapon-1 configure, Mfd1-Quad-gated), F5-F9=Mfd2 bank
   0x27-0x24+0x22 (page-gated gen A-D/mode), numpad flight cluster kept. DISPLACED from Cyd's
   map (each reachable on the panel or by editing bindings.txt): number row→secondary panel,
   QWERTY row→pilot keypad (dropped), arrows→hat looks (arrows now drive), V/C/B→fire
   0x47/0x46/0x45, LCTRL→throttle-down. XInput pad section untouched.
   NOTE (control modes, authentic): in BAS mode the pod turns with the STICK (Q/E here) and the
   pedals are inactive; A/D turn in MID/ADV — exactly the manual's behavior, unlike the desktop
   bridge which re-routes A/D per mode.
4. Un-touched: CONTROLS.MAP, btinput defaults, pod serial path. `bindings.txt` is read only by
   `PadBindingProfile` inside the gated PadRIO TU — the pod build never opens it.

### Verification (2026-07-20, build-glass2, ARENA1 solo, all logs in-session)
- Panel: 0x0F→preset(0,1), 0x08→(0,0), 0x27→(1,1), 0x20→(1,0), zoom no-FAIL; 0x15 display
  1→2→0; 0x2C hold → `[flush] Reservoir level 6→0`; dead-class buttons (0x13/0x1A/0x12/0x14)
  silent as predicted. ZERO [FAIL] lines in the whole session (was 2 per bank press).
- Keyboard: W hold → thr 0→1, speedDemand 61.501, gait advances; Q → turnDemand 0.94 (BAS);
  M → `control mode -> 1`; A hold → turnDemand 1.0 (MID); Space → `[emitter] FIRED`; N →
  `display notify 1`; J/K/L → presets (0,1)/(1,1)/(2,1); H → reservoir drain; C → condenser#1
  valveState 1→5. BT_SHOT frame confirms visually: MID lit on the control-mode column, CRITICAL
  DAMAGE schematic up, MFDs on Eng pages, heading moved. V not re-injected (user took
  foreground mid-run) — code-identical to the verified backtick edge [T3].
- Suppression: typed 'w' swallowed (no [keych]), typed 't' flows ([keych] 0x74), WM_KEYUP
  VK_F5 swallowed (the 't'-alias hazard).
- Un-regression: build-pod (gates OFF) compiles 0 errors; forced-walk run drives
  (speedDemand=61.501, 32 subsystems, streamed ids 3→+0xdc / 4→+0xe4 unchanged).

## 2026-07-18 — Merge origin/master (commit f889e24): btinput meets PadRIO

Master's 33-commit run landed (D1 relay/operator-console line, CONTROLS.MAP+XInput binding
engine `btinput.cpp`, camera seats, torso pitch, sign fixes, the 1995 manual, version stamping).
**The reconciliation:** btinput (ungated, dev/pod desktops) joined the stand-down convention —
`BTInputPoll` yields and `BTInputSuppressKey` claims nothing when an operational cockpit device
(serial RIO / PadRIO) owns the input path (`BTRIODevicePresent`; `BT_KEY_BRIDGE` override;
forced harness exempt). **One input system per mode:** `CONTROLS.MAP`/btinput on dev+pod
desktops, `bindings.txt`/PadRIO on glass. The D1 relay keeps its own raw sockets by design
(relay and Steam are alternative wires; the BTNet seam covers the arcade mesh both need).
Verified: 3-config build, glass stand-down live, pod forced-walk with btinput active, 2-node
loopback MP 31/31.

## 2026-07-19 — Mission-control options: the AUTHORITATIVE catalog (TeslaSuite console.ini)

Source: `C:\VWE\TeslaSuite\410console\4_10-console-extracted\Console.ini`, the Mac 4.10 operator
console's `BT::` adventure tree (the `tag=` values are the egg field values; display names are the
console's). Cross-checked vs `410console/battletech-port/BATTLETECH-PORT-SPEC.md` + `reference/
cavern.egg`. This is every option the original console exposed for a BattleTech mission.

**Mission-level** — `[mission]`: `adventure=BattleTech` (fixed), `temperature=27` (fixed),
`scenario=freeforall` (the tag is always freeforall; the RESPAWN choice is the ROLE):
- map (8): cavern, grass, rav, polar3, polar4, arena1, arena2, dbase
- time (4): morning, day, evening, night   ← was day/night/morning/**dusk** (wrong: evening)
- weather (3): clear, fog (light), soup (heavy)
- role (2): Default (`model=dfltrole`, respawn) / NoReturn (`model=noreturn`, one life)
- length: seconds

**Per-pilot** — participant block:
- experience (4 [T1 game decode]): novice, standard, veteran, expert  ← was hardcoded `expert`
- vehicle (18, friendly→tag): Black Hawk=blkhawk, Loki=loki, Nova=bhk1, Mad Cat=madcat, Thor=thor,
  Owens=owens, Kotori=own1, Summoner=thr1, Hellbringer=lok1, Timber Wolf=mad1, Avatar=avatar,
  Satyr=ava1, Sunder=sunder, Sunder V1=snd1, Vulture=vulture, Mad Dog=vul1, Mischief=lok2,
  Zanin Neko=mad2  (the 18 ModelList names; matches the 2026-07-18 vehicle sweep)
- color/camo (7, display→tag): White=White, Black=Black, Brown=Brown, Red=**Crimson**, Green=Green,
  Gray=**Grey**, Tan=Tan   ← was White/Black/Crimson only
- badge/emblem (7, the `badge=` field): VGL, Davion, Kurita, Liao, Marik, None, Steiner  ← was `VGL`
- patch/badge-color (8, the `patch=` field): Yellow, Blue, Grey, Green, Violet, Red, White, Black
  ← was `Yellow`
- dropzone (5, the `dropzone=` field): one, two, three, four, five  ← was `one`
- advancedDamage (0/1): the advanced damage model toggle  ← was hardcoded `1`
- vehicleValue: 1000 (const), loadzones=1 (const), bitmapindex (per-pilot ordinal)

---

## 2026-07-20 — Per-display cockpit windows (BT_GLASS_PANELS)

**Goal (Cyd):** stop collapsing the desktop cockpit into combined surfaces. Break each
SECONDARY display out into its OWN window carrying that display's surface WITH its RIO button
bank placed around it, arranged pod-faithfully around the main 3D view — a dev cockpit that
reads like the pod, so button/lamp/display behavior can be validated in position.

**New TU: `engine/MUNGA_L4/L4GLASSWIN.{h,cpp}`** (BT_GLASS-only; added to the CMake BT_GLASS
`target_sources`). Builds SEVEN GDI windows and positions them around the main window:

| Window | Surface (port) | RIO bank | Buttons |
|---|---|---|---|
| Heat MFD (UL)    | `Heat` (0x4000)        | 0x28-0x2F           | 8 red, 4 above / 4 below |
| MFD 2 (UC)       | `Mfd2`/`Eng2` (0x0400) | 0x20-0x27           | 8 red, 4 above / 4 below |
| Comm MFD (UR)    | `Comm` (0x8000)        | 0x30-0x37           | 8 red, 4 above / 4 below |
| MFD 1 (LL)       | `Mfd1`/`Eng1` (0x0100) | 0x08-0x0F           | 8 red, 4 above / 4 below |
| MFD 3 (LR)       | `Mfd3`/`Eng3` (0x1000) | 0x00-0x07           | 8 red, 4 above / 4 below |
| Secondary/Radar  | `sec` (palette, portrait) | 0x10-0x1B Secondary | 12 yellow, 6 left / 6 right |
| Flight Controls  | (none)                 | 0x38-0x47 (+ panic/icom) | neutral, 2 columns |

**Architecture — GDI + CPU blit, NO D3D for the secondaries.** Each window is a layered,
topmost GDI window (the L4PADPANEL pattern: double-buffered paint, ~62 ms repaint timer,
left-click = momentary / right-click = latch → `PadRIO::SetScreenButton`; lamps from
`PadRIO::GetLampState`). The surface is CPU-expanded from the shared gauge pixelBuffer by the
new **`SVGA16::ExpandPlaneToBGRA(mask, paletteID, monoTint, rotateQuadrant, dst, &ow, &oh)`**
(L4VB16.cpp) — the no-D3D analog of `DrawDevSurface`: palette-LUT expand for `sec` (monoTint
< 0), mono bit-plane → tint for the MFDs; the portrait secondary CRT is unrotated by
transposing into `dst` (rotate 1/3, `BT_GAUGE_SEC_ROT`) — then `StretchDIBits` (HALFTONE) into
the surface rect. An Mfd/Eng pair shows whichever plane is the live (non-`BlankColor`) one, as
on the pod monitor. This reuses the plasma-window CPU→window pattern and sidesteps the whole
D3D dev-composite bug family (additional-swap-chain lifetime, device-state save/restore,
depth-stencil mismatch, layered strobing).

**Gate: `BT_GLASS_PANELS`** (runtime env; `BTGlassPanelsActive()`). Default ON under
`-platform glass` (preset putenv in `btl4main.cpp`); `=0` restores the legacy single pad panel
+ docked gauge strip. Wired at three seams:
- `L4PADRIO` ctor: `BTGlassPanelsActive()` → `BTGlassPanels_Create()` instead of
  `BTPadPanel_Create()`; dtor destroys both (safe no-ops).
- `L4VB16`: `BTDrawGaugeInset` / `BTGaugeWindowRenderAndPresent` early-return when
  `GlassPanelsOwnSurfaces()` (the per-display windows own the surfaces).
- `btl4main`: skip the `gBTGaugeDockBottom` + 1100×600 world-window forcing (world stays
  normal size — no bottom strip).

**Placement.** `ComputeLayout()` rings the windows around `ghWnd` (the main game window):
top row Heat/Mfd2/Comm above it, Mfd1/Mfd3 at the lower corners, radar below-center, Flight
Controls left of the seat; clamped to the work area, with an 800×600-centered fallback before
the main window exists + a one-shot reposition once `ghWnd` comes up (in the repaint timer).

**Verified [T2 startup].** `-DBT_GLASS=ON` Debug build links (the usual `/FORCE` mech3
subsystem set is pre-existing, unrelated). Bounded `-platform glass -egg DEV.EGG` launch:
`[glasswin] per-display cockpit up (7 windows: 5 MFD + radar + flight)`, `[plasmawin] … up`,
`[padrio] XInput pad found`, no failure/abort markers, full mission loop un-regressed (killed
after 18 s). Visual layout / surface content / click-through NOT yet human-verified.

**Tunable (Cyd flagged refinements):** surface display sizes, the exact button sub-positions
around each screen, the yellow left/right split (first cut 0x10-0x15 / 0x16-0x1B), and the MFD
mono phosphor tint — all named constants at the top of `L4GLASSWIN.cpp`. Deferred: folding the
plasma window into the same arrangement; per-window draggable/saved positions; moving/resizing
the main window into a true center cell for a tighter ring.

### Blank-surface bug (found + fixed same day) — /FORCE duplicate-global race

First glass-panels run showed the buttons but BLANK display surfaces. `BT_GLASS_LOG`
diagnostics in `BlitSurface` traced it stage by stage: `application == 0x00000000` in
`L4GLASSWIN.cpp` for the ENTIRE run (call 1 → 481), so `application->GetGaugeRenderer()` was
never even reached. Yet the legacy dock path (`BTDrawGaugeSurfaces`, `L4VB16.cpp`, SAME engine
lib) logged `application=047BA9C8 gr=0C57FF78` — non-NULL.

Root cause: the 1995 headers declare free globals (`application`, `ghWnd`, …) without
`inline`/`extern`, so they are DEFINED in both `munga_engine` and `bt410_l4`. Under
`/FORCE:MULTIPLE` the linker binds each `.obj`'s reference to one copy or the other
**non-deterministically per link** — the newly-added `L4GLASSWIN.obj` bound the copy the game
never assigns (stays NULL), and a relink even flipped `L4VB16.obj`. Routing through an engine
helper is therefore unreliable (its binding is equally random).

Fix: `BTResolveGaugeRenderer()` / `BTResolveMainWindow()` (declared in `l4vb16.h`) are DEFINED
in `game/btl4main.cpp` off the launcher's OWN file-scope pointers — `btl4App` (set to `new_app`
at btl4main.cpp:631) and the global `hWnd` (the real main window). Those live in `btl4main.obj`
and are the actual assigned pointers, so the resolvers are always correct regardless of the
duplicate-symbol binding. `BlitSurface` and the placement code call the resolvers, never the
`application`/`ghWnd` globals. New durable gotcha: `context/reconstruction-gotchas.md` §6
duplicate-GLOBAL corollary.

Verified after the fix (`BT_GLASS_LOG`): `[glass] 'Heat MFD' port=Heat mask=0x4000 pal=3
enable=2 ow=640 oh=480 nonzero=22227/307200`, `[glass] 'Secondary / Radar' port=sec mask=0x3f
pal=1 enable=3 ow=480 oh=640 nonzero=26206/307200` — surfaces resolve and carry live pixels.
`BT_GLASS_LOG` left in as a permanent per-surface resolve/pixel diagnostic (throttled).