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re: test the port's black-backdrop predicate disc-wide -- exact locally, rare globally

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sylpheed-port proposed that a screen declaring a full-screen .prm at t=0 with
fade == 0xff000000 is standalone, and one without it is composited: 12/4 across
their sixteen exported screens, every exception independently known to be
composited. They asked for it against archives they do not have. That is my lane.

CONTROL: the predicate reproduces their split exactly. GP_TITLE's sixteen bundles
give 12 with and 4 without, the four without being entries 0, 1, 2, 3 --
build_00, build_01, press_start, press_start_jp -- and the element names match
(pteff00.prm, palogo_eff0.prm, pgloading_eff00.prm). Independent derivation from
the disc, not a re-run of their tool.

DISC-WIDE it is rare: 76 of 965 screen builds, 7.9 %. GP_STAGE_CLEAR 4/4,
GP_SYSTEM 2/2 and GP_TUTORIAL 2/2 are all-yes; GP_HANGAR_ARSENAL is 0 of 390, and
GP_READY_ROOM, GP_OPTIONS, GP_PAUSE_MENU and GP_GAMEOVER are all zero.

So it is not a general standalone/composited test. GP_OPTIONS and GP_PAUSE_MENU
are screens a player plainly sees as screens and declare no backdrop; read as
"composited" the rule would make 92 % of the game's screens composited, which the
archives do not support. What it appears to separate is narrower: screens that
BEGIN FROM BLACK from everything else. A pause menu over gameplay, a hangar over a
3D scene and a plate over a title all lack a backdrop without being the same kind
of thing -- the negative class is heterogeneous, which is what a two-way rule
cannot express.

For the port: exact within GP_TITLE, so --black for those twelve is justified from
the file rather than assumed; do not carry it into the four archives they have yet
to export, where in three of them it classifies every screen alike.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v
This commit is contained in:
sylph-decoder
2026-08-30 17:36:10 +00:00
parent a1af583725
commit 82b20bc51d
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55
docs/re/data/black-backdrop-predicate.txt Normal file
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# Does a screen declare its own OPAQUE-BLACK backdrop? Disc-wide. 2026-08-30.
# instrument: crates/sylpheed-formats/examples/black_backdrop_predicate.rs
# predicate: some .prm element holds fade == 0xff000000 at t=0.
#
# sylpheed-port proposed this as a rule separating STANDALONE screens from
# COMPOSITED ones, split 12/4 across their sixteen exported screens, and asked
# for it to be tested against archives they do not have.
#
== CONTROL: GP_TITLE's 16 composable bundles (port reports 12 with, 4 without)
entry 0 no
entry 1 no
entry 2 no
entry 3 no
entry 4 YES pteff00.prm
entry 5 YES pteff00.prm
entry 6 YES pteff00.prm
entry 7 YES pteff00.prm
entry 8 YES pteff00.prm
entry 9 YES pteff00.prm
entry 10 YES palogo_eff0.prm
entry 11 YES palogo_eff0.prm
entry 12 YES pgloading_eff00.prm
entry 13 YES palogo_eff0.prm
entry 14 YES palogo_eff0.prm
entry 15 YES pgloading_eff00.prm
-> 12 with, 4 without
== DISC-WIDE, over every screen build
GP_BUNK.pak 6 / 8 declare a black backdrop
GP_CHALLENGE.pak 6 / 78 declare a black backdrop
GP_DEBRIEFING_PILOTLOG.pak 0 / 18 declare a black backdrop
GP_DIALOG.pak 34 / 105 declare a black backdrop
GP_GAMEOVER.pak 0 / 10 declare a black backdrop
GP_HANGAR_ARSENAL.pak 0 / 390 declare a black backdrop
GP_LEADERBOARD.pak 0 / 4 declare a black backdrop
GP_MAIN_GAME_D2D.pak 0 / 18 declare a black backdrop
GP_MAIN_GAME_E2D.pak 0 / 18 declare a black backdrop
GP_MAIN_GAME_F2D.pak 0 / 18 declare a black backdrop
GP_MAIN_GAME_I2D.pak 0 / 18 declare a black backdrop
GP_MAIN_GAME_J2D.pak 0 / 18 declare a black backdrop
GP_MAIN_GAME_S2D.pak 0 / 18 declare a black backdrop
GP_MISSION_LOG.pak 0 / 4 declare a black backdrop
GP_MISSION_SELECT.pak 2 / 66 declare a black backdrop
GP_MOVIE_THEATER.pak 2 / 56 declare a black backdrop
GP_OPTIONS.pak 0 / 14 declare a black backdrop
GP_PAUSE_MENU.pak 0 / 6 declare a black backdrop
GP_READY_ROOM.pak 0 / 60 declare a black backdrop
GP_SAVE_LOAD.pak 10 / 18 declare a black backdrop
GP_STAGE_CLEAR.pak 4 / 4 declare a black backdrop
GP_SYSTEM.pak 2 / 2 declare a black backdrop
GP_TITLE.pak 8 / 12 declare a black backdrop
GP_TUTORIAL.pak 2 / 2 declare a black backdrop
76 of 965 screen builds disc-wide declare an opaque-black backdrop (7.9 %)
--- END ---