docs/re: mark the paint-order item solved, and say what is left

The item that has been open through this whole run is answered: the paint order
is the screen object's reordered child array at +0x30, not any table in the file.
BACKLOG and INDEX now lead with that, and the investigation behind it is kept in
full underneath — most of it refutations, which is what made the answer findable.

What is left is stated in the same breath, because it is what the port needs:
deriving that order from the bundle without running the game. Until then the
viewer paints in declaration order and the title screen composites wrongly, which
is now a documented defect rather than a mystery.

docs/re/BACKLOG.md

@@ -6,6 +6,25 @@ unknown, what evidence exists, and what the first step would be. Move an item in
 
 ---
 
+## ✅ SOLVED (2026-08-19) — the paint order is a runtime child list, not a table in the file
+
+The screen object the game builds at load time holds **two** lists of its
+elements: the declaration-ordered array at `+0x08`, and a **reordered child array
+at `+0x30`** — and the second is the paint order. Read live off the title screen
+and checked against the draw capture: the seven nameable elements sit at child
+slots 0, 6, 7, 13, 16, 17, 22, strictly ascending, in exactly the captured order.
+See [`structures/ui-screen-runtime.md`](structures/ui-screen-runtime.md).
+
+**Still open, and it is what the port actually needs:** deriving that order from
+the bundle without running the game. The order is structured (elements sharing a
+sprite are adjacent; full-screen effects lead), so it looks derivable, but no
+rule has been found. Until then the viewer paints in declaration order and the
+title screen composites wrongly — a known, documented defect rather than a
+mystery.
+
+The investigation that got here follows, kept in full because most of it is
+refutations that were worth the cost.
+
 ## The declaration table is not a paint order on every screen
 
 **Found 2026-08-17**, building the Explorer's UI Screens browser on

docs/re/INDEX.md

@@ -25,7 +25,7 @@ Promote to a prose `structures/…md` file when a format needs behavioural notes
 | Unit (craft/vessel) fields defaulted on disc | ✅/🟡 | [runtime struct](structures/unit-struct-runtime.md) | The parsed `unit\UN_*.tbl` definition object, vtable `0x820af844`, ≥`0x380` bytes, one per unit — **discovered, not assumed** (`unit_discover.py`), and distinguished from the spawned-entity class `0x820af030` by being one-per-ID and byte-constant within a run. Across runs only pointer words move — `--crosscheck` proves **no reported field offset is run-dependent** (two words, `+0x2c8`/`+0x2d0`, are stage-dependent and remain unidentified). 27 fields ✅ (21 units, 7 runs); the `Maneuver` block is **schema declaration order, 4 bytes/field, base `0x9c` with a two-slot gap after `AA_Roll_Min`** (29 anchors, 0 conflicts), which also pins 5 fields *no* disc record ever values. Angles are **radians at runtime, degrees on disc**. **Re-derived independently 2026-08-13 from the loader's own key strings** (`sub_82341A20`; the field name for each store is a string in the image): **159 fields**, agreeing with this solver on **25 of 25 shared offsets**, verified at **406 values matching the disc and 0 disagreeing** over 11 live objects spanning UNIT and VESSEL — landed as `data/unit_definition_layout.txt` + `sylpheed_formats::unit_layout` + a no-emulator test, with **121 defaulted fields** read out ([live-unit-definitions](live-unit-definitions.md)). Unlike weapons, unit definitions are instantiated **per stage**, so coverage (21/110) grows by visiting missions — but a defaulted field is **not** a global constant: `Size_Y` provably inherits `Size_X` (7 independent units, 6 distinct values), and three more sibling rules are recorded ❔, recovering 65 values in units never visited — [values](captures/unit-runtime-fields.csv) |
 | Arsenal develop economy | ✅/❔ | [arsenal-develop-economy](arsenal-develop-economy.md) + [conditions](captures/arsenal-develop-conditions.csv) | The Arsenal reads `weapon.tbl` (item ids, in the 8-category display order) and `strings.tbl` (names, descriptions, and a **"Conditions to obtain"** block per item) out of `GP_HANGAR_ARSENAL.pak`. All **60** conditions are extracted: gates are stage completion, a predecessor item, or an **ace kill**; costs run 3 000–350 000 P and **20 items are free** once gated. `weapon.tbl`'s first record reproduces the in-game DATA SHEET exactly (Range D / Power E / Speed – / Weight 0.3 = Light / 4000 P) — later records are unreadable from the string pool alone because IDXD **dedupes repeated values**. Used to identify the save blob's index space, now **solved**: the blob follows **`strings.tbl`'s** order — the display order *plus* the cut items only the localisation file lists (`Adhesive Mine B2A`, `Ballista GSH`, …) — pinned by four hand-written probe saves (9 Stiletto, 21 Falcon, 39 Tomahawk, 48 Jamming System) and closing exactly at index 53. `weapon.tbl`'s id list is **not** the index space; that it is also 54 long is a coincidence, and the two agree only to index 32. The retail save's five unexplained owned entries are the cut items, shipped owned and never rendered |
 | UI screen layout (`.rat`) | ✅/🟡 | [ui-rat-layout](structures/ui-rat-layout.md) | One pak per UI screen; each RATC = one (context × language) build; every `<name>.t32` sprite has a `<name>.rat` **layout record** (BE u32; 1280×720 design space; scale/tint/X/Y, keyframes for animated elements, `opt ` link to the focused state). **The tutorial PAUSE menu and the title main menu both rebuild pixel-accurately from the disc.** `loop1.rat` is decoded — it is a **looping sprite animation**, not a composition. ⚠️ **DEMOTED 2026-08-18** — the declaration table is *not* the paint order: a per-draw capture of the running title screen ([ui-title-paint-order-capture](ui-title-paint-order-capture.md)) paints element 13 first and elements 0/1 late, and the visible screen composites two bundles. The rest of the table's reading stands. Previously claimed: the **screen's draw list is the RATC bundle's own declaration table** (elements in back-to-front order, including the `eff*`/`deli*`/`msg` sprites that have no `.rat`, and excluding focused button variants reached via `opt `); its entry also carries a **parent element index** at `+32`. **A screen is fully reconstructible from its bundle**: the placement region right after the declaration table gives every element a keyframe group (header = element index + keyframe count, then 40-byte blocks of scale/tint/X/Y), including the `.rat`-less sprites — verified 11/11 on the tutorial pause bundle, with `pgp_ttrl_btn10`'s inline (546,288) matching its own record exactly |
-| UI screen paint order | ✅/🟡 | [title paint order](ui-title-paint-order-capture.md) | **Measured from the guest's draw stream** (Canary hook `log_ui_draws`, F10): the title paints 11 draws a frame through one sprite shader, in an order its bundle does not describe — declaration order, reverse order, keyframe-start, resting-time, resting-Y, the placement region, the RATC child order and *every other build's table* are all refuted, the quads carry **z = 0** so there is no depth key, and no field in the bundle orders them. The main menu was captured too but cannot discriminate. 🟡 the rule is still unknown and the remaining route is the guest code. Bonus: per-quad **alpha** matches the bundle's resting fade, and only the two visibly animating elements change α between frames |
+| UI screen paint order | ✅ | [runtime screen object](structures/ui-screen-runtime.md) + [title capture](ui-title-paint-order-capture.md) | **SOLVED**: the game's screen object keeps a second, reordered list of its elements — the child array at `+0x30` — and that is the paint order, not the declaration table. Read live from guest memory (found by the item vtable `0x820b30b4`) and checked against the draw capture: the seven nameable elements sit at child slots 0, 6, 7, 13, 16, 17, 22, strictly ascending, exactly as captured; it also settles the one pair no static field could order. 🟡 deriving that order from the bundle — what the port needs — is still open |
 | Scripted input / profile traps | ✅/🟡 | [canary-scripted-input-traps](canary-scripted-input-traps.md) | Why a scripted run appears unable to press Ⓐ: **F10 opens the emulator menu bar**, and any Xenia UI makes `XamInputGetKeystrokeEx` return SUCCESS with an empty keystroke *before* any driver is asked (Canary now logs `[RE-INPUT] … swallowed by IsUIActive`); the title needs a **signed-in profile** (hence `--create_profile_if_none`); and a **FIFO trace consumer that exits stalls the emulator**, which reads exactly like a dead pad. 🟡 The main menu HAS been reached — Ⓐ works, but only intermittently (1 in ~4), which is the open question |
 | Title-screen guest crash | ✅ | [title-crash-stl-tree](title-crash-stl-tree.md) | The guest throws **`std::out_of_range`** from its cache-manager flush (`sub_823070B0`, an STL map/set erase that builds `'invalid map/set<T> iterator'`); the access violation after it is only the throw **returning**, because this build does not unwind guest EH. Trigger found and controlled: an **incomplete on-disc cache** (`~/.local/share/Xenia/cache/aab216c3`) throws ~100 s into a boot, a complete one never does — 2 runs each way. ❌ `mem_watch`, the handoff's suspect #1, is **eliminated**: cold cache + `--mem_watch=false` throws anyway |
 | Save file (`savedata`) | ✅/❔ | [savegame-format](structures/savegame-format.md) + [`tools/re-capture/savegame.py`](../../tools/re-capture/savegame.py) | `GDHA` container, zlib payload, chunk stream (`GDAA` / phase name / `GHAD` 122 B progress block / 16×20 B slot table / trailer). **Container and layout read off the title's own serializer `0x822C00E8` and verified by a byte-identical round-trip**; the whole save is 545 B. Payload offsets are also the live save object's offsets (`save+8` GHAD, `save+136` slots). A second save made in-game names **Points** (+24), **flight time in ms** (+4) and **clear ratio %** (+8) off the game's own Details panel; the payload is a **pure function of game state** (same state saved twice = byte-identical, only the header FILETIME and its uninitialised pointer padding move), and the 16 `SHAB` records are **not** the UI's 20 save slots. Difficulty vs stage is undecided — three fields hold 2. **A third save, taken after developing exactly one Arsenal weapon** (Light Machine Gun MG I, 4000 P), moves exactly three things: `+24` Points 4101→101 (which **separates it from `+28`**, that did not move), `+8` clear ratio 5→6 (so the ratio counts *collection*, not only stages), and two entries of the 54-byte blob — `2→4` for the item bought and `0→2` for the successor the game announced as newly developable, giving the blob its alphabet ✅ *0 locked / 2 developable / 4 developed* (only the `4`s are stored — `2` is re-derived at load). **Saves can also be written back**: three derived header fields (length at `+0x30`, payload length at `+0x8c`, `adler32` at `+0x8e`) are all that stand between a parse and a hand-written save that the title loads, and [`savegame_edit.py`](../../tools/re-capture/savegame_edit.py) re-wraps a real save byte-identically. That turned the blob's index space from blocked-on-story-progress into four probe saves — see the [economy note](arsenal-develop-economy.md) |