Sylpheed/docs/re/structures/ui-group-start-time.md

❔ A group's DURATION is in the data; its START TIME is not

Status: ✅ the durations are measured and match; ❔ the start offset is undecodable from the placement data, with the obvious candidate refuted.

Found while testing whether the splash timeline, played, reproduces the capture sequence — the last gap in the animation model.

The durations are right

From the 235-frame draw capture of the developer splash, at the settled 2 units/frame, under the shifted time reading:

element	drawn on frames	= units	declared visible span	match
palogo_gamearts_eff, palogo_seta_eff	94–115 (22)	44	~0 … 45 = 45	97.8 %
palogo_gamearts, palogo_seta	116–211 (96)	192	15 … 210 = 195	98.5 %

(The logos are a = 0 until t=15, so they are drawn for 15…210; the glows fade in from their untimed first keyframe.) Each element is on screen for its declared span, to within 2 %.

🔴 But they do not share a clock origin

Every glow declares the same times — 15, 30, 45 — and every logo the same 15, 30, 190, 194, 206, 210. On one clock they would overlap almost entirely: both families start at 15.

They do not overlap at all. The glows run frames 94–115 and the logos 116–211 — strictly sequential, the logos starting the frame after the glows end. Fitting a single origin bears this out: gamearts_eff needs f₀ ≈ 93.5 and gamearts needs f₀ ≈ 103, about 19 units apart, and the same edit that aligns one throws the other off by ~9 frames at both ends.

🔴 The obvious candidate is refuted

parse_placements reads each group header as (element index, keyframe count) followed by one undecoded lead-in word. That is exactly where a per-group start offset would live. It is 0x00000000 for all seven elements of the developer splash — glows and logos alike. It carries no offset.

❔ So where does the start come from?

Not from the keyframe times (identical across each family), not from the group header's spare word (zero), and not from declaration order (eff0.prm, gamearts, gamearts_eff, seta, seta_eff, anima, anima_eff — which interleaves logos and glows, while the observed sequencing groups them). The RATC child order does not match the observed order either.

Reach: three places looked, all negative. What remains is that the sequencing is driven by code, consistent with what boot-config-and-gamepart-registry already concluded for the boot order — the driver is code, not data.

⚠️ What a port needs to know

A group tells you how long an element's animation runs and what it does; it does not tell you when that animation starts relative to other elements on the same screen. On the developer splash the observed order is: both glows together, then both logos together. That is a measured sequence for one screen, not a decoded rule — a port animating a screen has to author the sequencing, and should know it is authoring.

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✅ Verified against its own refutation — and it goes further than start times

2026-08-29. Two checks on the "sequential, not simultaneous" reading.

The phases really are disjoint

If the glows and logos ever shared a frame, the sequencing claim would be wrong. Across all 235 captured frames, the number of frames containing both a glow and a logo is zero. The switch is a single clean boundary:

f110–115   1280x720 + 262x108 + 525x90     ← both glows
f116–122   1280x720 + 243x86  + 499x72     ← both logos

Two sprites either side, no overlap, no transition frame.

A third of the bundle is never drawn at all

Entry 11 declares three logo/glow pairs. Only two are ever drawn:

sprite	declared	drawn
palogo_gamearts / _eff	500×71 / 521×91	95 / 22 frames
palogo_seta / _eff	240×89 / 261×110	95 / 22 frames
palogo_anima / _eff	388×136 / 407×156	never

…and palogo_anima declares the same keyframe times as palogo_gamearts. ⚠️ Reach: the capture covers frames 1–214, so this is "never within the window", not "never". The pair may follow after it.

What that means for a consumer

A bundle is a palette, not a script. Its elements carry what to draw and for how long; which of them run, and when each starts, is decided outside the placement data — selectively enough that two elements with byte-identical keyframe times get 95 frames and 0 frames in the same run.

That is the same conclusion the boot-order work reached from the other end (the driver is code, not data), now with a per-element measurement behind it.

⚠️ Concretely: compositing every element of a bundle does not reproduce what the game shows over time. It is the right thing for a static screen that settles, and it is not a timeline.

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🔴 Narrowing "a bundle is a palette" — the mechanism is NOT established

2026-08-29. The glow phase and the logo phase are disjoint, but there are two explanations and I asserted one of them:

1. one bundle, selective activation — the game runs some of entry 11's elements, then others;
2. two bundle-loads in sequence — the game shows one composition, then another (entries 11 and 14 are twins declaring identical sprites).

The draw log records each draw's texture base, which looked like it would separate them. It does not:

phase	frames	texture bases
publisher splash	1–90	0x11C30000, 0x10000000
glows	94–115	0x11C30000, 0x10000000
logos	116–211	0x11C30000, 0x10000000

The test fails its own control. The publisher splash is certainly a different bundle from the developer splash — different entry, different artwork — and it uses the same base. So 0x11C30000 is a reused upload address, not a bundle identity, and it cannot distinguish hypothesis 1 from hypothesis 2.

What survives, and what I withdraw

✅ Survives: a bundle's declared elements are not what gets drawn. palogo_anima and palogo_gamearts carry byte-identical keyframe times, and in the same run one is drawn for 95 frames and the other for none — whichever of the twins was active declares both. The phases are also strictly disjoint (0 frames of overlap in 235).

🔴 Withdrawn: the mechanism. "One bundle, elements activated selectively" was my reading, and the evidence does not choose it over "two compositions shown in sequence". The practical consequence is the same either way — compositing every element of a bundle does not reproduce what the game shows over time — but the why is not established and should not have been stated as though it were.

❔ What would separate them: a per-draw capture recording the bundle each draw came from, or a kernel/file-IO log showing whether a second RATC entry is read between frames 115 and 116.

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✅ Re-established, by elimination — selective activation is happening

2026-08-29. The alternative can be killed statically, which I had not tried. Hypothesis 2 needs a bundle that declares the glows without the logos. There is none. Enumerating every entry in GP_TITLE that contains palogo elements:

entry	elements
10, 13 (publisher twins)	palogo_eff0.prm, palogo_sqex, palogo_sqex_eff
11, 14 (developer twins)	palogo_eff0.prm, all three logos and all three glows

Four entries, and each developer entry declares the complete set of six. So whichever bundle was active across frames 94–211 — entry 11, entry 14, or both in turn — it declared the logos and the glows, while the game drew two sprites at a time in disjoint phases.

⇒ Only a subset of a bundle's elements is drawn at any moment, whatever the bundle-loading story is. The conclusion does not depend on resolving how many bundles are involved, which is why the texture-base test's failure no longer matters.

✅ So "a bundle is a palette, not a script" is reinstated — this time by eliminating the alternative rather than by assuming it away. The route that worked was not a better capture but asking what the competing hypothesis would require on the disc, and finding it absent.

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✅ The measured splash sequence — what a port has to author

Since the sequencing is not in the placement data, here is the measurement, so a port authors from evidence rather than from taste. Frames are VdSwap counts; 1 frame = 1/30 s (2 units/frame × 1 unit = 1/60 s, both settled in Q1). Data: data/splash-phase-timeline.txt.

phase	frames	n	seconds	starts at
publisher — palogo_sqex	1–90	90	3.00+	0.00
(gap — nothing drawn)	91–93	3	0.10	3.00
developer — both glows	94–115	22	0.73	3.10
developer — both logos	116–211	96	3.20	3.83

⚠️ Three limits on these numbers.

• The capture opens at frame 1 with palogo_sqex already at a=255, so the publisher phase began before the window. 3.00 s is a floor, and every "starts at" is relative to the capture, not to boot.
• palogo_anima and palogo_anima_eff get 0 draws in all 214 frames, so the third logo pair's phase — if there is one — is not in this measurement.
• One capture, one run. The glow→logo switch is a single frame boundary with no overlap, which is a strong shape, but the durations are one sample each.

✅ What is solid: the 0.73 s glow phase and the 3.20 s logo phase are each within 2 % of their element's declared span, so the durations are the bundle's own and only the sequencing is authored.