# Pad documentation

Three documents, kept at the level of *what, why, and invariants* — not
line-by-line code — so they stay true as the implementation evolves.

| Doc | What it is |
|---|---|
| [`spec.md`](./spec.md) | What the app **actually does**, measured performance, the code layout, and an explicit list of deferred features. |
| [`architecture.md`](./architecture.md) | How it works: single-owner concurrency model, channel topology, Frame handoff contract, ownership rules, editor/browser/render internals. |
| [`development_plan.md`](./development_plan.md) | The active plan: completed phases, remaining work, and the on-device observation loop. |

## Package inventory

| Package | Role |
|---------|------|
| `internal/editor` | Chunked buffer, line index, virtualized viewport, IME ops, autosave, logic goroutine, state, Frame |
| `internal/browser` | Directory browsing, search, sort, pagination, browser state machine |
| `internal/ui` | Element tree, frame layout, renderer (op-based), IME wiring, gestures |
| `internal/perf` | Default-off performance profiler (per-logic-frame cadence + scroll state → CSV) |
| `internal/io/pool` | Worker pool (8 workers, 2 priority lanes) + file/dir tasks |
| `internal/test/e2e` | Harness driving the real `Logic` + `Inspect` |
| `cmd/pad` | `main.go` (entry), `impl_android.go` (base path) |

## Documentation policy

1. **Docs describe invariants and contracts, not code lines.** If a document
   has to change on every refactor, it is too detailed — delete it or raise
   its level of abstraction. Point-in-time implementation plans are deleted
   once implemented (the previous `*_implementation_plan.md`,
   `touch.md`, `element_model.md`, `layout_rendering.md`,
   `virtual_scroll_render_optimization.md`, and `conflict_resolution.md` were
   removed in the 2026-08 doc reorganization for this reason).
2. **Unbuilt behavior is not spec'd.** Requirements that are not in the code
   live in `spec.md` §7 (deferred), never as if they worked.
3. **Code wins.** When doc and code disagree, fix the doc.

## Build & install (Android, this workstation)

Prereqs on this box (already installed): JDK 17, Go, Android SDK at
`~/android-sdk` (platform-tools, build-tools 35.0.0, emulator, NDK),
`gogio@v0.10.0` in `~/go/bin`, `apktool` at `/tmp/apktool.jar`, debug
keystore at `~/.android/debug.keystore`. Env vars are set in `~/.bashrc`.

The full recipe is `/tmp/build_pad.sh` (machine-local). Steps:

1. `gogio -target android -targetsdk 35 -arch amd64 -o /tmp/pad-raw.apk .`
   (from `cmd/pad/`)
2. `apktool d /tmp/pad-raw.apk -o /tmp/pad_decoded -f`
3. Inject `<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE"/>`
   into the decoded `AndroidManifest.xml` (Android 15 needs it for
   `/storage/emulated/0`).
4. `apktool b /tmp/pad_decoded -o /tmp/pad-unsigned.apk`
5. `apksigner sign --ks ~/.android/debug.keystore --ks-pass pass:android
   --key-pass pass:android --ks-key-alias androiddebugkey --out cmd/pad/pad-emu.apk /tmp/pad-unsigned.apk`
6. `adb install -r cmd/pad/pad-emu.apk`

Run the emulator (headless, AVD `pad_avd`, API 35):

```
nohup emulator -avd pad_avd -no-window -no-audio -no-boot-anim \
  -gpu swiftshader_indirect >/tmp/emulator.log 2>&1 &
```

App package/activity: `pad.pad / org.gioui.GioActivity`. Default root
directory: `/storage/emulated/0/Notes` (push test files there with
`adb push file /storage/emulated/0/Notes/`).

## On-device observation loop (quick reference)

Gio renders into one GL surface, so the authoritative debug signals are
data, not pixels:

- `adb logcat -s pad.pad` — app log (IME commits, open-file timing, errors).
- `adb shell input tap|swipe|text` — drive the UI (see `development_plan.md`
  for the tap coordinates and IME-tap cadence that works).
- Autosave debounce is 1 s: **wait ~1.6 s before reading a file back from
  disk** after typing.
- Memory: `adb shell dumpsys meminfo pad.pad` (watch PSS/RSS; the 3.8 GB
  emulator OOMs the app above ~2.5 GB RSS).
- Screenshots (`adb exec-out screencap -p > /tmp/x.png`) are an auxiliary
  check only — state, logcat, and file diffs are authoritative.