a112bc9feb
Chasing why (A) does not advance the title turned up four harness bugs, one real
root cause, and a refutation of that root cause as the explanation.
FIXED, each verified:
* boot_menu.sh sent the emulator stdout to /dev/null, which is why none of the
rest was visible. It now keeps a log and prints its path.
* skip_intro.sh probed pixel (625,618) for the green (A) glyph - a 1280x720
coordinate. screenshot returns the 1279x675 game surface, where that point
is on the copyright line and reads (8,17,31). Symptom: a 600s TIMEOUT with
the title on screen. Now classified with screen_id.py; next boot printed
"TITLE at 239s -> A".
* skip_intro.sh no longer taps through the movies. Making that press real (the
vgamepad fix) was a REGRESSION: the boot then reached the title in 90s and
that title accepted nothing. menu_draw_capture.sh records the same finding
independently.
* boot_menu.sh signs in whichever profile exists instead of a hard-coded XUID.
ROOT CAUSE FOUND: naming a XUID with no profile behind it opens a sign-in
dialog, xam_dialogs_shown_ goes to 1, and IsUIActive() then discards every
XamInputGetKeystrokeEx. Measured 8,388,601 swallowed calls in one boot with the
pad log showing presses arriving normally throughout. Only B13EBABEBABEBABE
exists on disc; the script asked for E0300000EFBEA3D4. Signing in the real
profile takes the swallow count 8,388,601 -> 0.
AND REFUTED: that is not why the title is stuck. With a valid profile and zero
swallowed keystrokes, a single (A) on the title that ends the boot still does
nothing. The dialog bug was real and worth fixing; it is not the explanation.
Next probe is specific: --log_mask=13 records no kernel calls, so it is not even
known whether the game polls at the title. A log on the SUCCESSFUL
XamInputGetKeystrokeEx return, mirroring the one already on the swallow path,
answers it in one boot.
Reverse-engineering knowledge base
This directory is the spec-side of the clean-room: it records what the original Project Sylpheed binary does (behaviour) and how its data is laid out, so that the Rust port can be implemented from these specs without re-deriving anything and without ever copying original code.
It exists to answer one question fast: "do we already know how X works, and how sure are we?"
The one rule that matters
Never document a claim more confidently than the evidence supports, and never paste original code here.
A wrong-but-confident note is worse than no note: someone builds on it and the bug hides for weeks. Every entry therefore carries an explicit confidence and its evidence. This mirrors the project method — measure the oracle, never infer; refute before believing.
Clean-room firewall
- ✅ Allowed: behaviour descriptions, field offsets/types, formulas, state machines,
observed input→output pairs, and references to the original by address
(
sub_821B68C0) or toxenia-rs/sylpheed.db. - ❌ Forbidden here and in
crates/: pasted decompiled C/C++ or verbatim disassembled function bodies presented as the thing to reimplement. Cite the address; describe the behaviour in your own words. Disassembly is a tool for understanding, not a source to copy.
Confidence levels
| Level | Meaning | Bar to reach it |
|---|---|---|
CONFIRMED |
Behaviour verified against ground truth. | ≥2 independent observations or one observation cross-checked against an oracle (canary framebuffer, a known-correct value, a second code path). |
PROBABLE |
Strong single-source inference. | One clean observation, or an unambiguous static read of the disassembly. |
HYPOTHESIS |
Educated guess, not yet tested. | Anything else. Must say what would confirm/refute it. |
Promotion requires new evidence, not re-reading the old evidence. A HYPOTHESIS that
"looks right again" is still a HYPOTHESIS. Only an independent check promotes it.
If evidence later contradicts an entry, demote it and record the contradiction — do
not silently edit the conclusion.
When to document
- Right after a function/structure crosses from
HYPOTHESISto at leastPROBABLE— before moving to the next code path, so the knowledge isn't lost or re-derived. - Whenever confidence changes (up or down) — append to the Evidence log, don't overwrite.
- Not while it's still a pure guess with no evidence — a one-liner in the relevant backlog/plan is enough until there's something to stand on.
What to document
- Functions/code paths →
docs/re/functions/<name>.md(one file per function or tight cluster). - Data structures / formats →
docs/re/structures/<name>.md. - Keep the index in
INDEX.md(one line each: name · confidence · one-line summary).
Use the templates: _TEMPLATE.function.md,
_TEMPLATE.structure.md.
How we find and confirm code paths (the toolchain)
Everything joins on the guest virtual address (PC) — code addresses are fixed by the XEX load, identical across our emulator and canary.
- Static (cheap, try first):
xenia-rs/sylpheed.db(DuckDB: 25 481 functions, xrefs, strings, vtables, imports). Query withxenia-rs/zq.py—zq.py grep <str>,zq.py xref <addr>,zq.py dis <lo> <hi>,zq.py fn <pc>. Entry points are usually a string (zq.py grep MSG_DEMO) or an import (movie/XMA API) xref'd back to the loader. - Dynamic (when static is ambiguous): run
xenia-rswith its probe suite —--pc-probe/--audit-pc-probe-hex(fires at block entry),--mem-watch(mid-block reads/writes of a VA),--lr-trace(call/return chains),--trace-instructions,--dump-addr(read guest memory). These already exist; prefer them over hacking canary. - Oracle (correctness ground truth): canary — the Wine cross-build
xenia-canary/build-cross/bin/Windows/Debug/xenia_canary.exe(the native Linux ELF crashes / does not run — do not use it). This is the only emulator that reaches the in-game menu; ourxenia-rsnever got past the intro video. Use canary to observe output (capture its framebuffer for texture colours), not usually to instrument code — though itsbuild-crosstoolchain does compile, so small C++ probes + rebuild are possible when needed. Run muted, one emulator process at a time, point it at the real ISO (not the symlink).
⚠️ VA-equality caveat: join code by PC (fixed), but never assume a data VA holds the same bytes across emulators — allocators differ. Compare data by content/layout.