# A screen build is not the only thing `compose` can draw

**Status:** ✅ `CONFIRMED` by measurement over the disc, with the artifact to
show for it. 🟡 the wider set is not "all screens" — most of what it adds are
fragments. ❔ what distinguishes a screen from a fragment in the file is unknown.

## The gap

`ui_layout::is_build` — the predicate every screen command and every disc test
enumerates with — requires a `.rat` layout child:

```rust
ratc::is_ratc(bundle) && kids.iter().any(|c| c.name.ends_with(".rat"))
```

The **developer-logo splash** has none. Its elements name their `T8aD` sprites
directly (`palogo_gamearts.t32`), so there is nothing for a `.rat` record to
place, and `parse_build` handles it perfectly well — it was simply never reached.

That was worse than a missing screen. The splash is **one of only two screens
whose paint order has been read off the running game**
([`ui-paint-order-key.md`](ui-paint-order-key.md)), and it is the one where the
layer key explains the *whole* permutation. Its measurement could not be checked
against a render, because there was no way to produce one.

## The measurement

| | count |
|---|---|
| RATC bundles on the disc | 2 859 |
| pass `is_build` | 965 |
| pass `is_composable` (declaration table + a resolvable `T8aD`) | 2 751 |
| passing `is_build` but **not** `is_composable` | **0** |

So the new predicate is a strict superset, not a rival rule.

**But the 1 786 extra bundles are not 1 786 screens.** They are dominated by
two-element fragments — a button beside its glow:

```
GP_READY_ROOM.pak  +792     GP_MAIN_GAME_*2D.pak  +108 each (six languages)
GP_DEBRIEFING_PILOTLOG.pak  +164     GP_HANGAR_ARSENAL.pak  +96
  e.g.  2 els: ["pvbtnnew.t32", "pvbtnneweff.t32"]
        2 els: ["py_menu_new.t32", "py_menu_new_eff.t32"]
```

That is why `is_build` stays the default. Widening it would also **renumber
`--build`** for every pak, and the corpus's notes cite build indices by number
(`GP_TITLE` build 4, entries 11/14, `GP_OPTIONS` build 11) — silently shifting
them would invalidate written-down evidence.

## What landed

`ui_layout::is_composable`, and an opt-in `--all` on `screen list`, `screen info`
and `screen render`. Default behaviour and default numbering are unchanged.

```
$ sylpheed-cli screen render dat/GP_TITLE.pak splash.png --all --build 11 --black
build [11]: drew 6/7 elements
  not drawn (1): ["palogo_eff0.prm"]
```

![the splash](../captures/ui-layout/developer-logo-splash-composed.png)

All three logos with their glows behind them. The seventh element is a `.prm`
primitive, which has no sprite and is **skipped by this composite** — 🔴 ~~"skipped
as everywhere else"~~, **corrected 2026-08-31**. That phrasing was true of *our
compositor* and false of *the game*: the element is `palogo_eff0.prm`, and
[`ui-forced-backdrop.md`](ui-forced-backdrop.md) decodes it as the **full-screen
opaque black backdrop, forced FIRST — opaque at 211 instants, below 6 of 6, and
that order is measured off the running game**. It does not skip; it paints, and it
paints under everything.

> ⚠️ **Why this line and not the ones around it.** The load-bearing claim on this
> page — the draw order `[2,4,6,1,3,5]`, pinned by a disc test and matching the
> oracle — got the scrutiny. The aside did not, *because it carried no weight*.
> `sylpheed-port` named the mechanism after importing an unchecked aside of mine
> into an authored file: **a claim that carries no weight attracts no scrutiny**,
> and then it sits being read as measured. Found by sweeping this corpus for
> decorative generalisations ("as everywhere else", "the usual") after they did. A disc test
pins the draw order to `[2,4,6,1,3,5]` — the glows first — which is the order
measured off the running game, so the measurement is now checkable rather than
merely recorded.

Note this render also depends on the `_eff` fix
([`ui-focus-and-effect-elements.md`](ui-focus-and-effect-elements.md)): before
it, the three glows were dropped as "focused-state records" and the splash would
have rendered as three bare logos.

## What is not settled

* ❔ **What makes a bundle a screen.** `is_composable` answers "can this be
  drawn", not "is this a screen the game shows". Element count is a crude proxy
  (fragments are 2–5 elements) and has not been checked against anything.
* ❔ **The `.prm` primitives.** `palogo_eff0.prm` is a full-screen element with
  pivot (640,360) and a single keyframe; nothing decodes `.prm` yet, so every
  composite is missing whatever they draw. On the splash the measured paint order
  puts it **first**, i.e. it is the backdrop.
* 🟡 The splash render has not been diffed against a framebuffer capture. It is
  now *possible* to, which it was not before.