Watch de-duplication (per the plan review): FileObserver (inotify,
push) and MediaStore ContentObserver (URI push) are the ONLY change
detectors. Removed: the 100 ms recv_timeout tick, the fast_dir_sig
mtime-diff watcher, collect_watched_dirs, changed_dirs, dir_sig,
rescan_subtrees, and the 5-minute full-rescan timer thread.
watch_files now blocks on the push channel; on Android each wake
coalesces ~50 ms so a burst of N file events becomes one payload
batch, one SQLite connection, and ONE grid emit (verified on the
emulator: 20-file copy = 1-2 emits, 20-file delete = 1 emit,
single add still lands in ~75-95 ms).
FileObserver rewritten: recursive registration (Pictures/DCIM tree,
cap 5000 dirs) and self-extending — a CREATE/MOVED_TO on a directory
spawns a new observer for it, so new albums are watched too.
tif/tiff added to the image filter.
Dead code removed (the Tauri port never wired them): scan::walk,
walk_dir_nostats, walk_dir_into, mtime_ns, decode_jpeg (full-size),
images::thumb_png, db::set_thumb, db::list_entries, db::count,
db::delete_by_media_id; Thumb shrunk to {rgb,width,height} (the
grid is uniform squares; the viewer uses full-res). Tests now
compile (tempfile dev-dependency was missing — the test module
never built) and were fixed to match the current API.
Viewer: live swipe preview — while a horizontal drag is in flight at
fit scale, the picture being swiped in renders on the page strip
(second <img>, its grid thumb, a ~1 ms mem hit) and tracks the
finger, so there is no blank side. On commit the primary image takes
over from exactly where the preview was; on snap-back the preview
slides back with the tween. Verified on the emulator (two images
visible mid-drag, clean slide home).
Not re-verified: 120 Hz jank (per instruction — measure once when
settled). Desktop paths untouched (deferred).
Root causes found via per-event tracing (trace.log) + heartbeats:
1. Decode backlog: single worker at ~300ms/photo could not keep up with
fast long scrolls — phone session ended with a 2400-deep queue
draining at ~3 cells/s (13+ min to catch up). That was the
'scroll far down and nothing loads no matter how long I wait' zone.
- 4 parallel decode workers (~12 photos/s)
- viewport-aware stale drops: prefetch jobs more than 60 rows behind
the viewport are dropped, not decoded (fleeing leaves no backlog)
- Q_CAP bounds the queue; JS 1.5s safety net re-requests
- queue peak in repro test: 42 (was 2405); all 850 decodable
emulator images now load (708 before)
2. Stale-anchor bug: sendAnchor was leading-edge throttled with no
trailing call — if a scroll ended inside the 150ms window the Rust
anchor stayed stale forever, and the worker then dropped fresh
URGENT jobs (tap → full read) as 'off-screen'. Fix: trailing
anchor send; and URGENT jobs are never stale-dropped (only
prefetch work is droppable).
3. Viewer latency: full-res read ran on Chromium's main thread
(wry shouldInterceptRequest is synchronous) — 30-50MB flash read
froze the whole WebView. Now: thumb shown instantly (mem cache,
~1ms), full read queued urgent and done off-main; full-ready event
swaps in the full-res (256MB full-res LRU makes re-opens instant).
Measured click→full-res: 4ms on emulator.
4. Scan: skip OS junk (._* AppleDouble forks, dotfiles) — the phone's
DCIM carried 72 of them, rendering as permanent gray cells.
5. Viewer for a corrupt file now shows 'image unavailable' instead of
'loading…' forever; grid retry timers skip far-off-screen cells.
Chromium owns scroll/compositor/lazy-load/image-cache; Rust owns
scan/SQLite/thumbnail-decode behind a gallery:// custom protocol.
Hard-won gotchas (see in-code comments):
- Android: no native custom-scheme support → wry rewrites the URL to
http://gallery.localhost/... (custom_protocol_workaround). The JS
MUST request that form; the handler receives the reverted
gallery://localhost/... and must strip the authority.
- tauri_build::build() in build.rs must run UNCONDITIONALLY (build
scripts run on the host: a cfg(target_os) gate silently disables it,
which skips the rustc-cfg=mobile emission → no mobile_entry_point →
.so with no JNI symbols → UnsatisfiedLinkError).
- build.rs must list frontend files for rerun-if-changed (a dir-level
directive only watches the dir mtime, not content edits) — the .so
bakes the frontend at compile time and cargo otherwise ships stale
UI with a 'successful' build.
- logcat drops ~75% of lines under load: use the file trace.
- fetch() is CORS-restricted (page origin http://tauri.localhost);
<img> is not — add ACAO:* anyway.
Emulator (5853 real files): grid renders, lazy thumbs via
gallery:// with on-disk cache (87 files 35-72KB), FR log clean at
60Hz, viewer opens full-res with compositor-only pan/zoom. The single
'broken' cell is a 17-byte fake test JPEG (correct behavior).
