# BTL4APP.CPP — reconstruction notes (2026-07-18)

**Status: 12/12 functions reconstructed; the binary's `Fail()` line constraint (BTL4APP.CPP:400)
is met exactly.** Source basis: decomp `BT411/reference/decomp/all/part_014.c:8052-8425`,
port semantic map `BT411/game/reconstructed/btl4app.cpp`, surviving headers BTL4APP.HPP /
L4APP.HPP / BTL4MODE.HPP / BTL4ARND.HPP / BTREG.HPP / L4CTRL.HPP / CONTROLS.HPP / MODE.HPP /
APPMSG.HPP / RPL4VID.HPP / RENDERER.HPP / LATTICE.HPP, idiom exemplars AUDSRC.CPP /
BTL4ARND.CPP / L4MPPR.CPP / BTMSSN.CPP.

## Address map (source order = binary emission order) [T1]
| line | function | @addr | size |
|---|---|---|---|
| 100 | ctor | 4d34c4 | 72 |
| 116 | dtor | 4d350c | 44 |
| 125 | MakeRegistry | 4d3538 | 44 |
| 138 | MakeVideoRenderer | 4d3564 | 76 |
| 165 | MakeAudioRenderer | 4d35b0 | 100 |
| 189 | MakeModeManager | 4d3614 | 48 |
| 202 | MakeControlsManager | 4d3644 | 72 |
| 228 | MakeGaugeRenderer | 4d368c | 56 |
| 249 | MakeMission | 4d36c4 | 48 |
| 264 | MakeViewpointEntity | 4d36f4 | 824 (anchor; Fail @ line 400 ✅) |
| 461 | RunMissionMessageHandler | 4d3a2c | 104 |
| 476 | StopMissionMessageHandler | 4d3a94 | 224 |

Note the CPP emission order differs from BTL4APP.HPP's declaration order (ModeManager before
ControlsManager before GaugeRenderer in the binary) — the binary order wins. [T1]

## Decoded constants — all resolve to named 1995 expressions [T1]
- ctor base arg `1` = `BTL4` (`enum ApplicationID {RPL4, BTL4, BTW4}`, APPMSG.HPP:47 — note
  the unreleased **BTW4** slot).
- `0x50421` = `BTL4ModeManager::ModeInitial`; `0x400000` = `ModePlasmaDisplay`; the +8/+4
  writes = `ModeManager::AddModeMask/RemoveModeMask` inlines (MODE.HPP:56-70, byte-exact).
- `2`/`4` = `LBE4ControlsManager::{PrimaryThrustMaster, PrimaryRIO}` (L4CTRL.HPP IOType).
- `-1` mode mask = `ModeManager::ModeAlwaysActive` (MODE.HPP); keyboard registration =
  `ControlsUpdateManager<ControlsKey>::Add(ModeMask, Receiver*, MessageID, Plug*)`
  (CONTROLS.HPP:319; the vtbl+0x14 call on `keyboardGroup[KeyboardPC]` @manager+0x1a0).
- Video ctor 5-tuple = `(DefaultRendererRate, MaxRendererComplexity, DefaultRendererPriority,
  VisualInterestType, 1)` — signature from RPL4VID.HPP; the two leading globals are
  DAT_004e8238/DAT_004e823c (extern consts, RENDERER.HPP:38/41). ⚠ the PORT's btl4app.cpp
  maps these to the WRONG positions (globals as args 4-5) — flagged for back-porting.
- Audio ctor = `(GetFrameRate(), GetMissionReviewMode())` — BTL4ARND.HPP:95 proves arg2 is
  `Logical mission_review_mode`; DAT_004fd550 = `L4Application::missionReviewMode` static.
  `GetFrameRate` naming for FUN_0044e19c is [T3] (port identification, not header-proven).
- All string literals byte-verified via section_dump (51ebd6…51ed40), including
  `"*****Mech has no controls mapping!*****"` and the camera/mech `"Thrustmaster"`/`"L4"`
  mapping names.

## Judgment calls (flagged, not proven)
- **Banner** copies the stale `rp4lbe4.cc` RP-clone banner because the surviving BTL4APP.HPP
  carries the matching stale `rp4lbe4.hh` banner — the pair was cloned from RP together. [T4]
- Include list & order mirror the port's reconstruction, trimmed to 1995 headers. [T4]
- `switch` vs `if/else` for the two class cases compiles identically at -O; switch chosen to
  match VWE style elsewhere. [T4]
- Camera-case mapper resource = stack `SubsystemResource` (decomp-proven: 32-byte name copy,
  classID 0xf, modelSize 0x30); mech-case mappers take a **CString name** (decomp-proven:
  CString ctor + refcount at the call) with `ClassID`/`SharedData` DEFAULTED (0x7dc,
  &DefaultData passed by the compiler). [T1 shape / T3 default-arg reading]
- `mech_mapper = NULL;` after `Fail()` reflects the decomp's `puVar3 = 0` (Fail returns in
  OPT?); kept. [T1]
- `description->resourceAddress` / `ControlMappingsListResourceType` (== 6) member/constant
  names follow the port's ResourceDescription reading; verify against the 1995 RESITEM/RES
  headers when that TU is done. [T3]
- Two `Check*` lines were omitted in MakeViewpointEntity to meet the line-400 constraint;
  Check macros are invisible in OPT builds so the choice is evidence-neutral, but WHICH
  lines the original spent is unknown — revisit if a Borland build ever line-checks. [T4]

## Line-constraint ledger
`BTL4APP.CPP:400` = the only Fail in the TU ✅ met exactly.