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re(ui): the rest fallback fires on 2 elements, and "last keyframe" wins there

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Scored candidate rest-pose rules by rendering and correlating instead of
arguing, and both results correct something I had published.

First, the exposure. The guessing fallback is reached only by an element
that is plateau-less AND multi-keyframe -- a single-keyframe element
short-circuits at `match len { 1 => first }`. Per screen:

  title (4)               24 elements   2 plateau-less   0 reach the fallback
  main menu (5)           16            5                0
  EXTRAS (6)              18            5                0
  publisher splash (10)    3            2                1
  developer splash (11)    7            2                1

So on the three screens the port cares most about, rest() never guesses.
That is why three different rules render builds 4/5/6 to identical
correlations -- the code is unreachable there, which I nearly read as
"the choice does not matter".

Second, where it does fire, the last keyframe is markedly better:

  publisher splash   dwell +0.9600   last +0.9982   maxalpha +0.9600
  developer splash   dwell +0.9643   last +0.9758   maxalpha +0.9643

That refutes my own earlier refutation. I had killed the last-keyframe
rule by arguing it makes palogo_anima_eff invisible while its two
siblings stay lit, which looked like an artefact. The capture says
otherwise: making it invisible is what improves the match. The sibling
symmetry was my expectation, not evidence.

Caveat kept in front: both captures are single frames of a transient
animation, so this fixes which pose matches THOSE frames, not which is
canonically at rest. Default unchanged -- better on both screens where it
fires and identical on the other three, but it would move 2 305 elements
disc-wide on two measurements. Reachable via SYLPHEED_REST_RULE=last.

Also confirmed: all 195 zero-scale rest poses are inside the corrected
2 305 ambiguous population; none is a single-keyframe element.

METHOD: score a rule where it can differ, or you measure nothing; and an
argument from symmetry is a prediction, not a refutation.
This commit is contained in:
Sylpheed RE agent
2026-08-29 04:20:27 +00:00
parent 0265da31a1
commit 93e9b185ea
5 changed files with 114 additions and 2 deletions
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20
crates/sylpheed-formats/src/ui_layout.rs
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@@ -190,6 +190,26 @@ impl Element {
0 => None,
1 => self.keyframes.first(),
n => {
// ⚠️ EXPERIMENT GATE, default off. Both published alternatives to
// the longest-dwell fallback died by argument rather than by
// measurement, and `compose` can score a rule against the live
// captures — so they are reachable here to be tested.
// SYLPHEED_REST_RULE=last -> the final keyframe
// SYLPHEED_REST_RULE=maxalpha -> the most opaque keyframe
match std::env::var("SYLPHEED_REST_RULE").as_deref() {
Ok("last") => return self.keyframes.last(),
Ok("maxalpha") => {
let mut best = (0usize, 0u32);
for (k, f) in self.keyframes.iter().enumerate() {
let a = (f.fade >> 24) & 0xff;
if a >= best.1 {
best = (k, a);
}
}
return self.keyframes.get(best.0);
}
_ => {}
}
let mut best = (0usize, 0u32);
for k in 0..n - 1 {
let (Some(t0), Some(t1)) =

14
docs/port/HANDOFF.md
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@@ -404,8 +404,18 @@ authored version can be deleted.
and it is unambiguously their rest. Of the real 2 305, **195 get a degenerate
`scale = 0 %` pose**, and the two
candidate rules agree only **50.2 %** of the time.
✅ **This does not block you.** On the five screens the port needs, 14 elements
are affected and the candidate rules **agree on 13**. The single disagreement
✅ **This does not block you — your exposure is TWO elements, both on the
splashes.** The fallback is reached only by an element that is plateau-less
*and* multi-keyframe; a single-keyframe element short-circuits. Title, main
menu and `EXTRAS` reach it **zero** times, which is why three different
fallback rules render them to identical correlations. The publisher and
developer splashes reach it once each — and there, `SYLPHEED_REST_RULE=last`
(the final keyframe) scores **+0.9982** and **+0.9758** against the current
rule's +0.9600 and +0.9643. ⚠️ Measured against single frames of a transient
animation, so it fixes which pose matches *those* captures, not which is
canonically at rest. Default unchanged — it is better on both screens where it
fires and identical on the other three, but it would move 2 305 elements
disc-wide on two measurements. The single disagreement
is `palogo_anima_eff.t32` on the developer splash, and the current answer is
the defensible one there — see below. Still worth flagging plateau-less
elements in an export rather than silently inheriting our guess; it is one pass

12
docs/re/METHOD.md
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@@ -762,3 +762,15 @@ agent's loop prompt, i.e. nowhere durable. See [`README.md`](README.md) for the
It died the moment the rule was used to change a rendering, because the result
was visibly worse. If a measurement implies an action, take the action on
something you can score.
* **Score a rule where it can actually differ, or you will measure nothing.**
Three rest-pose rules rendered builds 4, 5 and 6 to *identical* correlations —
not because they agree, but because the code they change is unreachable on
those screens. The signal was on the two splashes, the only builds whose
elements reach the fallback at all. Identical results across variants is a
clue that the variant is not being exercised, not evidence that the choice does
not matter.
* **An argument from symmetry is a prediction, not a refutation.** I killed the
last-keyframe rule because it treats one of three sibling glows differently,
which felt like an artefact. Measured, it is the better rule on both screens
where it applies. Aesthetic expectations about how authored data "should" look
are worth stating as hypotheses and worth nothing as verdicts.

10
docs/re/REFUTED.md
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@@ -538,3 +538,13 @@ neighbourhood, not just the line.
unambiguously its rest. 1 502 of the 3 807 are those; the genuinely ambiguous
population is **2 305 (14.88 %)**.
[`ui-resting-pose.md`](structures/ui-resting-pose.md)
* "`rest()` for a plateau-less element should be the last keyframe → refuted by
the sibling argument" → **that refutation is itself refuted, this time by
measurement.** Rendering under the rule and correlating against the live
captures: publisher splash +0.9600 → **+0.9982**, developer splash +0.9643 →
**+0.9758**. Making `palogo_anima_eff` invisible *improves* the match; the
sibling symmetry was my expectation, not evidence.
* "the port's exposure to the rest-guessing defect is 14 elements" → **two.** The
fallback needs an element to be plateau-less **and** multi-keyframe; title,
main menu and `EXTRAS` reach it **zero** times, the two splashes once each.
[`ui-resting-pose.md`](structures/ui-resting-pose.md)

60
docs/re/structures/ui-resting-pose.md
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@@ -431,3 +431,63 @@ The same flaw is in the census this page published:
So the guessed-rest population is **2 305, not 3 807** — the published figure
overstated it by **65 %**. The defect is real and smaller than reported.
---
## ✅ Where the fallback actually fires — and "last keyframe" wins there
**2026-08-29.** Two things fell out of scoring rules by rendering instead of
arguing about them.
### The port's exposure is TWO elements, not fourteen
The guessing fallback is reached only by an element that is plateau-less **and**
has more than one keyframe — a single-keyframe element short-circuits at
`match len { 1 => first }`. Per screen:
| screen | elements | plateau-less | **reach the fallback** |
|---|---|---|---|
| title (4) | 24 | 2 | **0** |
| main menu (5) | 16 | 5 | **0** |
| `EXTRAS` (6) | 18 | 5 | **0** |
| publisher splash (10) | 3 | 2 | **1** |
| developer splash (11) | 7 | 2 | **1** |
On the three screens a port cares most about, **`rest()` never guesses at all**.
That is why three different fallback rules render builds 4, 5 and 6 to *identical*
correlations (+0.9500 / +0.9460 / +0.9440 for every rule) — the code is
unreachable there.
### On the two splashes, the last keyframe is markedly better
Rendering under each rule (`SYLPHEED_REST_RULE=last|maxalpha`, default off) and
correlating against the live captures:
| splash | dwell (current) | **last** | maxalpha |
|---|---|---|---|
| publisher | +0.9600 | **+0.9982** | +0.9600 |
| developer | +0.9643 | **+0.9758** | +0.9643 |
`maxalpha` is indistinguishable from the current rule; **`last` gains +0.038 and
+0.012**, and 0.9982 is very close to exact.
### 🔴 This refutes my own refutation
I had killed "rest = the last keyframe" by argument: on the developer splash it
makes `palogo_anima_eff` invisible while its two siblings stay lit, which looked
like an artefact. **The capture says otherwise** — making it invisible is what
improves the match. The sibling symmetry was my expectation, not evidence.
⚠️ **The caveat that keeps this honest:** both captures are *single frames of a
transient animation*. They fix which pose matches **these reference frames**, not
which pose is canonically "at rest" — a grab a second earlier would show the
glows. What the measurement supports is: for reproducing the committed captures,
use the last keyframe.
🟡 **Default unchanged.** The rule is better on both screens where it fires and
provably identical on the other three, but it would alter the rest pose of
**2 305** elements disc-wide and two of them have been measured. Reachable via
`SYLPHEED_REST_RULE=last` for anyone who wants to take that further.
✅ Unaffected by the earlier correction: all **195** zero-scale rest poses are
inside the genuinely-ambiguous 2 305 — none is a single-keyframe element.