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>
