Sylpheed/docs/port/HANDOFF.md

Handoff — what the menu port needs, and where it stands

The single page the port agent reads. Everything here is produced by the container agent's reverse engineering; nothing here is a design decision about the port itself.

Keep it current. It is a summary with links into docs/re/, not a second copy of the findings — but an answer that is not reachable from this page has not been delivered.

How to read an answer

Every row below is one of exactly three things, and the distinction is the point:

	meaning	what the port should do
decoded	a field on the disc, with a disc-wide check	read it from the data
measured	not on the disc in any form we found, but the running game does this	hardcode it, and cite this page
undecodable	we looked in these places, it is not there, here is the reach of the negative	author it by hand, knowingly

There is no fourth kind. If a row says measured or undecodable, the port is authoring that value, not transcribing it — and it should be kept somewhere a human can see it is a human decision, so that when it is later decoded the authored version can be deleted.

Status

	Question	State	Answer / link
Q1	keyframe time unit + ramp shape	✅ answered	ramp is linear; the clock advances 2 units per rendered frame; working conversion 1 unit = 1/60 s — ui-keyframe-time-unit.md
Q2	which build is which screen state	✅ answered	GP_TITLE is 8 screens shipped twice, EN/JP: 4/7 title art, 2/3 the PRESS Ⓐ plate, 5/8 main menu, 6/9 EXTRAS, 0/1 and 10/11 two unidentified DELTASABER plates — ui-title-build-map.md
Q3	paint order for the six screens	✅ answered	decoded: a u16 layer key at +0x0A of each T8aD sprite header, stable-sorted with declaration index; unkeyed elements get an implied key. Confirmed on 5 measured orders + EXTRAS vs a capture. One residual: the tie-break is unknown and bites on one element of the title — structures/ui-paint-order-key.md
Q4	button → GamePart	🟡 mostly answered	measured which screen each button opens (4 of 5; NEW GAME untested — it hangs). The GamePart id is a name match onto the decoded id table, not a measurement — menu-navigation-semantics.md
Q5	navigation semantics	✅ answered	measured: opens on TUTORIAL (not the top); ⬆⬇ one step, wraps both ends; ⬅➡ do nothing; Ⓑ returns to the parent with focus restored; Ⓑ on the main menu → title; Ⓑ on the title → nothing — menu-navigation-semantics.md
Q6	boot sequence + what drives it	🟡 partial	order observed, and the attract cycle is timed: ~8–10 s idle on the title → fade to black → ~85 s of video → title again, plate and all. The driver is still not decoded
Q7	transitions	❔ open
Q8	menu audio bindings	❔ open	cue table complete, event binding is not
Q9	video binding + playback rules	🟡 partial	ADV.wmv is the boot intro; new-game intro unidentified
Q10	music-bank sub-wave roles (intro+loop?)	❔ open	we concatenate blindly today
S1	Ready Room go/no-go	❔ open	probe not run

Already settled — the port can rely on these today

• GP_TITLE.pak is eight screens, each shipped twice — English and Japanese. Build 4 is the English title art and 7 its Japanese twin; 2/3 are the PRESS Ⓐ BUTTON plate, a build of their own composited over the title and faded in a beat later; 5/8 are the five-button main menu; 6/9 are the EXTRAS submenu — the only submenu inside this archive. Builds 0/1 and 10/11 are a DELTASABER / SYLPHEED A.I. plate that was never seen running, in the boot path, any title-side screen, or the attract loop. ✅ measured against live captures for the four English screens the boot path shows; ui-title-build-map.md. Withdrawn: the earlier "builds 6/8/9 are submenus" — 8 is the Japanese main menu. The other four main-menu buttons leave the archive (GP_SAVE_LOAD, GP_TUTORIAL, GP_OPTIONS, GP_MISSION_SELECT are the likely destinations by name — an inference, not a measurement).

• Buttons are identifiable as data. Element kind 0x3002 = button, 0x0 = decoration, 0x10 = primitive. ✅ decoded.

• Menu order is geometric. Buttons sorted top-to-bottom by resting Y. This is ✅ correct for a vertical menu and is not a decoded neighbour graph — the disc's real navigation structure is unknown, and opt is not a focus link (measured and refuted, see ui-focus-and-effect-elements.md).

• Highlighted states pair by name — ptbtn01.rat ↔ ptbtn01f.rat. 🟡 a naming convention that holds for all 54 real pairs, not a decoded field.

• The resting pose is the hold, not the first, last or longest-dwell keyframe; a keyframe is the start of a ramp. ui-resting-pose.md. ✅

• That ramp is linear, and it runs at 2 keyframe time units per rendered frame. Measured frame-by-frame off the running game's own draw stream: a declared 15-unit fade lands on round(255·k/15) for all seven of its samples, with k stepping 2, 4, 6, 8, 10, 12, 14 on seven consecutive submitted frames. measured, not decoded — the disc says t=30, it does not say what a t is. The seconds conversion (1 unit = 1/60 s, so a 30 fps screen) rests on a measured 27.6 present-frames/second and is the one part still worth re-testing; ui-keyframe-time-unit.md names the test. If it turns out the game presents at 60 Hz, every duration halves — nothing else on this page changes.

• The paint order is derivable from the file. Each T8aD sprite header carries a u16 layer key at +0x0A (the upper half of the 32-bit word at +0x08 is zero in all 21 184 sprites on the disc). Paint order is that key, stable-sorted so equal keys keep declaration order; elements with no sprite (.prm primitives, .tbm) have no key and take an implied one — the backdrop and dim quads sort early, the screen-transition fade (pteff00.prm, pfeff00.prm) sorts last. ✅ decoded. Checked against five paint orders read off the running game, one of them (GP_SAVE_LOAD's slot-list header, 6 instances) exact and independent of the screens the rule was fitted to, and against a fresh EXTRAS capture. It reorders 341 of the disc's 965 builds, so it is not a no-op dressed as a rule. 🟡 The one residual: ties. Where two elements share a key the game sometimes paints them in an order nothing predicts — eight candidates refuted, including declaration order, RATC child order, keyframe times, resting X/Y and kind. Measured cost: on the three screens with ground truth it changes the blend of one element on one screen (a title glow). Take the stable sort and accept that.

• Menu movement, measured off the running game. ⬆⬇ move one item per press and wrap at both ends (5-item main menu and 3-item EXTRAS both). ⬅➡ do nothing. Ⓑ goes up one level and restores focus to the item you came from; Ⓑ on the main menu returns to the title; Ⓑ on the title does nothing. The main menu opens focused on TUTORIAL, the middle item — 🟡 reproducible in this harness (2/2) but a third recorded run implies NEW GAME, so re-test before hardcoding it. All measured, none of it on the disc.

• Each button's destination is measured; its GamePart id is not. LOAD GAME → the save-slot list, TUTORIAL → the lesson list, OPTIONS → the settings menu, EXTRAS → GP_TITLE build 6, EXTRAS ▸ MISSION SELECT → the stage list. ❔ NEW GAME is untested — Ⓐ on it hangs the emulator. The GamePart ids (3, 25, 8, 5, 7) are the entries of the decoded id table whose names match the screens seen; that binding is authored, not measured.

• The GamePart id table — 29 entries at .rdata 0x820A1630, confirmed by the executable's own registration strings. ✅ This is the screen vocabulary; which button reaches which entry is Q4 and is not part of it.

• The logo splash is a screen, not a video. logo1–logo4 are manifest-bound with no .wmv on the disc. ✅

• Sprites carry their own labels. No font rendering or localisation is needed for this milestone. ✅ — and the localisation is already baked in: the Japanese screens are separate builds in the same pak, not a text swap.

Facts the port will trip over

• ADV.wmv is WMV3 video + WMA Pro audio, 1280×720 at 30 fps, 137 s. Godot 4 plays only Ogg Theora natively. How to handle that is the port's decision, not ours — but it is not optional.
• The disc holds 3.3 GB of video. Only the boot intro and the one new-game intro are in scope.
• Static.slb over-declares its size by 616 768 bytes — it is the highest-offset entry in sound.pak and its size field is an allocation size. A reader must allow a short read there and only there.
• Voice downmixes to mono, music does not. The left-channel downmix is correct for spoken lines and discards half a music mix.
• A music bank has several sub-waves and we glue them together. BGM_001 is 10 KB + 4.47 MB + 4.67 MB, concatenated into one 347 s track. Nobody has established whether those are intro + loop, two variations, or two halves — see Q10. Do not build menu looping on the concatenated track until it is answered.
• JNGL_001.slb does not decode. One bank in 9 519; its payload is not a whole number of XMA1 packets from any known data offset.

Reference data

Committed alongside the findings, so the port can be built without a disc in the loop during development:

• sylpheed-cli screen info --build <n> GP_TITLE.pak — the element table, per build, with pivots, kinds, focus links, keyframes and resting poses.
• sylpheed-cli screen render — the reference composite. When the port draws a screen, this is what it should be diffed against; where they disagree, one of them is wrong and the disagreement is worth reporting back.
• docs/re/captures/ — framebuffer captures of the real screens, for anything that has to be checked against the game rather than against our renderer.