Gitea #48 ROOT-CAUSED + FIXED: MFD "stray blocks / misplaced lamps" = uninitialized translation-table entries leaking pixels into other displays' bit-planes

The conviction was empirical, not theoretical: a new write-site trap
(BT_PLANE_AUDIT) in the seven L4VB16 drawing primitives logs any draw whose
color carries bits outside its port's plane mask -- the exact cross-display
corruption condition (Replace ORs an unmasked color; Or/Xor ignore the mask
entirely; And clears foreign planes).  A quiet solo session produced 15-30
leaks per minute:

    [plane] PORT 'sec' pixmap draw at(0,0) idx 217 entry=0xffffff00 mask=0x3f
    [plane] LEAK DrawPixelMap8[table] at(639,0) color=0xffffff00 mask=0x3f leak=0xff00

THE DEFECT: L4GraphicsPort::translationTable[256] is never initialized in the
ctor, and BuildSecondaryTranslation fills only the entries its BitWrangler
reaches -- 2^numberOfBits: 64 for the sec plane (mask 0x3F), 4 for the overlay
(0xC0).  Entries above that stay heap garbage.  Every draw resolves color
through this table, and the PIXMAP path indexes it with raw pixel values
0..255: the 480x640 radar background carries pixel index 217, whose garbage
entry's high bits (0xFF00 = ALL EIGHT MFD planes) were stamped into the shared
640x480 buffer -- invisible on the culprit page (the in-plane bits happened
dark) and visible as bright fragments at the same coordinates on every OTHER
display.  That is the operator's screenshot exactly: the same-position blips
on Mfd1+Mfd2 and the Heat-display block.

FIX (engine, both layers):
  * zero translationTable in the L4GraphicsPort ctor (plane-neutral default);
  * BuildSecondaryTranslation now cycles the in-plane pattern across entries
    [2^bits..255] -- high-index art degrades to its (index mod 2^bits) colour
    IN-PLANE and can never leak.  The 1995 binary ships the SAME 64-entry fill
    and survived on 6-bit art discipline; garbage is not a preservable
    behaviour, so the cycle-fill is a guarded PORT deviation (documented).

A/B PROOF: same probe, 60s -- 0 leaks after the fix (15-30/min before).
sim3 3-pod regression: zero crashes.

SECOND real defect found + fixed en route: sessions configure the CAMERA seat
first ("cameraInit" -- which includes the MISSION-REVIEW context:
configure(0, sec, 0, 0x00FF, native, rgb, mrpal.pcc), a DirectColor context
whose translation tables legitimately hold full RGB565 values spanning all 16
plane bits), and the viewpoint swap to the mech re-configured WITHOUT tearing
that tree down (btl4app's s_gaugeTreeBuilt latch treats the mech build as the
first).  The orphaned review gauges kept executing through stale DirectColor
ports.  BTL4GaugeRenderer::ConfigureForModel now overrides (ConfigureForModel
made virtual in L4GREND.h) and tears the prior entity-bound tree down before
every rebuild -- safe on first build, and the review screen rebuilds the same
way when the seat returns to the camera.

Also logged (open-questions): the review-screen PlayerStatus panels read the
compiled player at RAW BINARY OFFSETS (+0x1FC vehicle / +0x1C8 score /
+0x1C4 alive-dead box) -- the databinding trap, dormant until the review
screen runs; bridge before enabling the review.

Ruled out along the way (with evidence): the pilot-list label/erase geometry
(erase box 128x32 covers the 64x16 name rasters), the radar name labels
(view-level ClipImage clips them), PlayerStatus in-game execution ([ps] probe:
never runs in-game), and the PNAME bitmap dimensions (egg generator emits
64x16 exactly).

Why it "started with the comms feature" (#43): that wave registered the new
gauge classes with the config interpreter, letting more of the authored page
furniture parse and draw than before -- the leaking high-index pixmaps rode in
with it.  [T3 correlation detail; the leak + fix are T2 live-verified.]

Diagnostics kept (env-gated): BT_PLANE_AUDIT (the leak trap, now a permanent
regression tripwire), BT_PS_LOG, the port-level pixmap identity trap.

KB: gauges-hud.md (#48 section), decomp-reference.md (BT_PLANE_AUDIT),
open-questions.md (PlayerStatus databinding entry).  checkctx CLEAN.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
arcattack
2026-07-25 17:20:19 -05:00
co-authored by Claude Fable 5
parent 6f5a264835
commit 6bb03aed0b
7 changed files with 195 additions and 1 deletions
+7
View File
@@ -247,6 +247,13 @@ register. ⚠ The audit also flags the damage-economy item as SELF-CONTRADICTOR
lamps for the aux/eng bezel buttons (LAMP.cpp/L4LAMP.cpp are T0-compiled; the glass panels
+ pod RIO both consume `RIO::SetLamp`, so the flash lands on-screen AND on the pod).
Decode the type-31 stream format first — it names which conditions flash which lamps.
- **PlayerStatus (the mission-review panels) reads the compiled player at RAW BINARY OFFSETS
(2026-07-25, found via #48) [T1 code-read].** btl4gau3.cpp `PlayerStatus::Execute`:
`player+0x1FC` (vehicle), `+0x1C8` (score, drawn as a numeric), `+0x1C4` (alive/dead -- a
state flip draws a 160x240 filled box) -- all 1995 offsets, garbage on our compiled layout
(the databinding trap). DORMANT in-game (the review context no longer survives the viewpoint
swap -- the #48 teardown fix) but LIVE the moment the mission-review screen actually runs at
round end. Bridge all three through btplayer.cpp accessors before enabling the review screen.
- **Factory capability-roster loops 2-4 are STILL DEAD (task #57 discovery).** mech.cpp's
post-roster loops add to `heatableSubsystems`(0x51155c)/`weaponRoster`(0x511830)/
`damageableSubsystems`(0x50e4fc) through the local `SubProxy` stub whose `IsDerivedFrom`