Greg Pomerantz
c9a6066ace
Pixel 9 Pro (release aarch64, 8,577 photos): sustained 60 fps, 0 display hitches while scrolling, cold and warm cache. dumpsys gfxinfo reports 0 frames for Slint's NativeActivity window on Android 15 — document the dumpsys SurfaceFlinger --latency <layer> method instead.
471 lines
28 KiB
Markdown
471 lines
28 KiB
Markdown
# Gallery — development hand-off
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A high-performance image gallery for Android (primary), Linux and macOS,
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written in Rust with the **Slint** UI toolkit. This document is the starting
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point for development: it captures every decision, gotcha, and measurement
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from the framework evaluation that preceded it, so no learning has to be
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rediscovered.
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**Status: M3 done (2026-10-27)** — M0 scaffold, M1 metadata scan + sqlite +
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instant list paint, M2 thumbnail engine (turbojpeg DCT-shrink decode, worker
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pool, disk cache, cancellation), M3 grid UI (3-column ListView grid, shimmer
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placeholders, scroll-driven prefetch, memory-bound cell retention) all
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verified: 13 unit tests, 5k synthetic engine test, on the emulator (150
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real JPEGs: first paint 0.6 s cold, warm relaunch from disk cache, 0 ANRs
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through 16 fast swipes), and on a real Pixel 9 Pro (8,577 photos: grid
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renders, scroll = 60 fps with 0 hitches). Next: M4 viewer.
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---
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## 1. Goals
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- Browse and view a local photo collection (thousands of images) that stays
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smooth: instant grid, no decode jank, cached thumbnails.
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- Full-screen viewer with pinch-zoom/pan.
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- Correct EXIF orientation, HEIC support (Android camera default).
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- Same codebase on macOS + Linux (desktop `cargo run`) and Android
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(`cargo apk2`).
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- Quality of the *platform experience* matters: safe-area insets, IME-free
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UI, native-feeling widgets, animations — first-class support preferred over
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manual patching.
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Non-goals (for now): editing, cloud sync, video, widgets/live-updates.
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## 2. Why Slint (decision summary)
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Full evaluation in `/mnt/Backup/prog/android/ui/REPORT.md` (same tree:
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`~/prog/android/ui/REPORT.md`), raw notes in `NOTES.md` there. Headline:
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| | Slint 1.18.1 | eframe/egui 0.37.0 |
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|---|---|---|
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| Virtualized list (the gallery's lifeline) | ✅ `ListView` std-widget, only visible rows instantiated | ❌ `ScrollArea::show` lays out all children; `show_rows` = manual virtualization API |
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| Async image → UI | swap `slint::Image` into a property; only that tile redraws (retained mode) | `ctx.load_texture` + custom loader; visible set rebuilt every frame |
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| Lifecycle hook for permissions | ✅ `init_with_event_listener` (Start/Resume/Pause/Stop/SaveState/...) | ❌ none in `App` trait (winit swallows it) |
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| Android safe-area | ✅ `safe-area-insets` built in | manual 32px-ish panel workaround (winit#3910) |
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| Animation | ✅ declarative built-in engine | hand-rolled |
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| IME text entry | ✅ | ✅ |
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| APK size (release aarch64) | 8.57 MB | 2.87 MB |
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| Clean build time (x86_64, this machine) | 195 s / 270 crates | 76 s / 137 crates |
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| Desktop Linux system deps | `libfontconfig1` + `pkg-config` | none |
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| License | royalty-free for proprietary mobile/desktop (embedded excluded) / GPLv3 / commercial | MIT OR Apache-2.0 |
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| Min Android API | 26 | 24 |
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For a stateful, form-and-grid app, the declarative model was the right fit
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(see the discussion about `pad`'s immediate-mode frame friction); egui wins
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for games/dashboards and on APK size. Known Slint caveat: an open upstream
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"abort on pointer scroll" bug in the Android backend (`todo!()` in the
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pointer-event path) — verify it's fixed in 1.19 before relying on heavy
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scrolling; if it fires, the panic is obvious in logcat.
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## 3. Environment, build & test loop
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Everything below is verified working on this machine (2026-10-27).
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```bash
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export ANDROID_HOME=$HOME/android-sdk
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export ANDROID_NDK_ROOT=$HOME/android-sdk/ndk/27.0.12077973
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export PATH="$HOME/.cargo/bin:$ANDROID_HOME/platform-tools:$PATH"
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# Rust 1.99.1 via rustup; tools: cargo-apk2 1.5.0, cargo-ndk 4.1.2
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./scripts/build.sh debug # debug x86_64 APK + adb install + launch
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./scripts/build.sh # release x86_64 (emulator)
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./scripts/build.sh aarch64 # release aarch64 (device)
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cargo run # desktop (Linux needs libfontconfig1+pkg-config)
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```
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- Emulator: `emulator -avd pad_avd -no-window -no-audio -gpu off -no-snapshot`
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(google_apis x86_64, Android 15). **`-gpu off -no-snapshot` matters** —
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swiftshader_indirect + snapshot crashed the emulator once during the eval.
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If it won't start, the host key lost its wireless pairing — see the pairing
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procedure in `~/.pi/agent/AGENTS.md` (phone) / emulator docs (this AVD).
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- APK lands at `target/<debug|release>/apk/gallery.apk`.
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- Release signing uses the debug keystore
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(`CARGO_APK_RELEASE_KEYSTORE=$HOME/.android/debug.keystore`,
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`CARGO_APK_RELEASE_KEYSTORE_PASSWORD=android`) — fine for personal use;
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for Play, generate a real keystore and point the env vars at it.
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- `cargo apk2` quirk: `--target` (not `-t`). `--lib` builds the cdylib.
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- Grant "All files access" to the app on the emulator after install:
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`adb shell am start -a android.settings.MANAGE_ALL_FILES_ACCESS_PERMISSION`
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(or Settings UI). `adb install -r` keeps the grant.
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- **Emulator test data (M3)**: the AVD's `/Pictures/gallery-test/` has ~5k
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*fake* JPEG stubs (zlib garbage — they scan fine but fail to decode, good
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for volume tests). Real, decodable test JPEGs live in
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`/Pictures/realtest/` (150, generated with PIL). They were `touch`-ed to a
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future mtime so they sort to the TOP of the grid — when reasoning about
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"which cells should have images", remember only cells 0–149 are real;
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everything below is stubs and correctly shows shimmer. `adb push` of a
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directory nests a subfolder (push files individually or `mv` up);
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`adb shell touch -d '…'` works for setting mtimes. The thumb cache is at
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`/sdcard/Android/data/wow.gmp.gallery/files/thumbs` (wipe it to force
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re-decode).
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- Perf measurement: `adb shell perfetto` / `adb shell dumpsys gfxinfo wow.gmp.gallery`,
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`systrace`-style capture via Perfetto trace shell. Cold start:
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`adb shell am start -W`.
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## 4. Architecture
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The UI framework is only the display layer. The performance lives in the
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thumbnail engine, and it is framework-agnostic:
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```
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┌─ metadata ─────────────────────────────────────────────────────────┐
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│ sqlite (rusqlite, bundled): path, mtime, size, w, h, orientation, │
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│ thumb_path, date_taken — one background scan pass │
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└──────────────┬─────────────────────────────────────────────────────┘
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│ model → Slint (list of visible-range items)
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┌─ thumbnail pool (tokio-free: N std::threads, N ≈ cores/2) ─────────┐
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│ per job: token cancellation (AtomicU64 gen counter) + priority │
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│ 1. disk cache hit? .thumbs/{sha1(path|mtime|size)}.jpg → done │
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│ 2. decode AT TARGET SIZE (never full-size for the grid): │
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│ JPEG: zune-jpeg "turbo" (decode+downscale in ONE pass, │
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│ pure Rust, actively maintained) or turbojpeg (SIMD) │
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│ HEIC: imagepipe (0.5, 2026-08) — VERIFY Android NDK build │
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│ PNG: image/png │
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│ 3. apply EXIF orientation (once, here — never per frame) │
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│ 4. re-encode small JPEG → disk cache │
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│ 5. channel → UI: (id, slint::Image) │
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│ prefetch: decode visible ± 1 row; cancel items scrolled out │
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└────────────────────────────────────────────────────────────────────┘
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┌─ UI (Slint) ───────────────────────────────────────────────────────┐
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│ grid screen: ListView (vertical) → row of N square Image cells │
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│ viewer screen: full-size async decode (once, cached) + manual │
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│ two-finger pinch transform (no built-in in 1.18) │
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└────────────────────────────────────────────────────────────────────┘
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```
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Module layout:
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```
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src/
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lib.rs # android_main + platform init + scan/UI glue (M1/M2)
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main.rs # desktop entry [exists]
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main.slint # screens (split into ui/ components at M3) [exists]
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db.rs # sqlite schema + incremental scan apply [done M1]
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scan.rs # directory walk, image detection, walk_stream [done M1]
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thumb.rs # pool, dispatcher, disk cache, generation cancel [done M2]
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images.rs # turbojpeg shrink-decode, EXIF orientation, PNG [done M2]
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viewer.rs # full-size load + transform state (M4)
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perm.rs # storage permission check/request (M5)
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```
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Crate choices (all verified current on crates.io, 2026-10):
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| crate | version | why |
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|---|---|---|
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| `slint` / `slint-build` | 1.18.1 | pinned; upgrade to 1.19 after the pointer-scroll fix lands |
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| `rusqlite` | 0.41, `bundled` feature | SQLite without system deps; cross-compiles to Android |
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| `turbojpeg` | 1.5.1, `cmake` feature | libjpeg-turbo DCT-level shrink decode (1/2,1/4,1/8) — 48 MP at 1/8 peaks ~2.3 MB vs 137 MB full decode. Vendors + cross-builds libjpeg-turbo via CMake/NDK (verified). Chosen over `libvips` (same DCT shrink mechanism, +6–10 MB of .so files, LGPL, 4.3k downloads) and over `zune-jpeg` (no DCT shrink = full-size decode for 12 MP photos). |
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| `image` | 0.25, `default-features=false, png` | PNG thumbs + `imageops::resize` final fit |
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| `kamadak-exif` | 0.6 | EXIF orientation tag (all 8 values applied as pixel maps); `experimental::Writer` used only in tests |
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| `sha1` | 0.11 | cache keys |
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| `imagepipe` | — (deferred) | HEIC: the real device has **0 HEIC** files (9109 JPEG, 27 PNG), so HEIC support is deferred; `image` can gain `heic` or libvips can replace the JPEG path later — the engine API is decoder-agnostic |
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Decode sizes: grid tiles render at ~cell×2 (Retina) — e.g. 500 px side.
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Full-screen: full decode once (12 MP ≈ 30–80 ms off-thread, fine), cached in
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the in-memory LRU until memory pressure.
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**The five failure modes the current (unknown) app likely has** — this design
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eliminates all five: (1) full-size decode for grid cells, (2) no disk
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thumbnail cache, (3) no list virtualization, (4) decode on UI thread without
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cancellation, (5) EXIF rotation applied per frame.
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## 5. UI plan (Slint patterns)
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- **Grid**: `ListView` is the only virtualized std-widget (confirmed in
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source docs: "Only visible rows are instantiated"). Grid = vertical
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`ListView`, each row a horizontal layout of square `Image` cells
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(columns ≈ `floor(window-width / cell)`; recompute on resize).
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Cells bind `image <=> model.image` — when the pool delivers a thumbnail,
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only that cell invalidates (retained mode; no repaint calls to remember).
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- **Placeholder→image**: cell shows a `Rectangle` (shimmer optional, M6)
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until its `image` is set.
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- **Image cache**: Slint's built-in path-based LRU is 5 MB (`CLruCache` in
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`internal/core/graphics/image/cache.rs`) — too small and the wrong layer
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for us; our cache lives in Rust (disk + compressed-bytes LRU).
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No mipmaps in the Skia renderer — irrelevant since we pre-downsample.
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- **Viewer**: no pinch helper in Slint 1.18 (`TouchArea` has no pinch
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callback; grepped the stdlib). Manual two-finger math on `TouchArea`
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(distance/centroid → scale/translation, ~50 lines; crib
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`slint-src/examples/native-gestures` — source checkout is at
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`~/prog/android/ui/slint-src`, tag v1.18.1). Double-tap-to-zoom is a nice
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extra (M6).
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- **Screens**: single `Window` with a stacked layout (grid + viewer overlay)
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or a `Navigator`-style state property; keep it simple until M4.
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- **Safe area**: always pad with `root.safe-area-insets.{top,bottom}` (done
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in the scaffold).
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- **Animation**: use built-in `animate` statements (syntax: `animate <prop>
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{ duration: ...; easing: ...; }` — it is a *statement*, not an element).
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Slide/fade for the viewer is a one-liner.
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## 6. Slint 1.18 API gotchas (all hit firsthand in the eval)
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1. `animate` is a statement (`animate width { duration: 300ms; }`), not an
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`Animation {}` element.
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2. Text input widget is `LineEdit`, not `TextField`.
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3. Markdown interpolation: `text: "Count: \{count}"` (backslash-brace).
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4. `length` is the unit type for lengths (`property <length>`, not
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`logical<length>` in the 1.18 Rust API).
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5. No Rust macros/closures inside `.slint` callbacks — callbacks call global
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functions or invoke Rust via `@global` / imported callbacks.
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6. 1.18 ↔ 1.19 **docs drift** — when reading docs online, check which
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version; the local source at `~/prog/android/ui/slint-src` (tag v1.18.1)
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is ground truth for the pinned version. `git grep` beats the docs.
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7. `slint::android::init_with_event_listener(app, |event: &PollEvent| ...)`
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re-exports the whole `android-activity` crate as
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`slint::android::android_activity`; `AndroidApp` is also re-exported at
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`slint::android::AndroidApp`.
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8. `slint::Image` runtime construction: `Image::from_rgba8_premultiplied`
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(also `from_array`); assign to an `image` property to update a cell.
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9. Desktop Linux: needs `libfontconfig1` + `pkg-config` (pure Rust on macOS).
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10. Retained-mode redraw: changing a property re-renders only affected
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elements — design bindings so thumbnail delivery touches one property.
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11. **`in property` is NOT auto-bound to a same-named `for` variable.** In
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`for cell[c] in row.cells: CellView { ... }` you must write
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`CellView { cell: cell; ... }` — otherwise the component's `in property
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<Cell> cell` stays at its default (empty) and the cell renders blank
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while *looking* correct. (This silently broke M3 for an hour.)
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12. **Updating a nested model in place does NOT reach a ListView row that
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was recycled while off-screen.** In-place `inner.set_row_data(col, …)`
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updates only the currently-live `CellView`s; a row whose `GridRow`
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instance was recycled keeps showing stale cells until the next scroll.
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The reliable path is to replace the WHOLE outer row:
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`outer.set_row_data(row, Item { cells: ModelRc::new(VecModel::from(…)) })`
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— the outer `row_changed` makes the ListView re-bind `row-data` and the
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fresh nested read picks up the new state. Batch cell changes per row and
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do ≤ ~16 row-replacements per 100 ms tick (see `apply_row_batch`), or a
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fast scroll mass-updates and ANRs.
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13. `ListView` has no `spacing`/`gap` property in 1.18 — bake inter-row
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rhythm into the item height (we add a 4 px bottom margin inside
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`GridRow`; `ROW_SPACING` in lib.rs must match).
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## 7. Permissions & platform integration (Android)
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Declared in `Cargo.toml` (verified schema in cargo-apk2 1.5 / ndk-build2:
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`uses_permission` is **top-level** under `[package.metadata.android]`, and
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`Permission` supports only `name` + `max_sdk_version`):
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`READ_MEDIA_IMAGES`, `READ_EXTERNAL_STORAGE` (maxSdk 32),
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`MANAGE_EXTERNAL_STORAGE`.
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Runtime flow (M5), using the `ANDROID_APP` clone stashed in `src/lib.rs`:
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1. **MANAGE_EXTERNAL_STORAGE** (primary path, same as passgo): no runtime
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dialog exists — check `Environment.isExternalStorageManager()` via JNI,
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if false launch `Settings.ACTION_MANAGE_ALL_FILES_ACCESS_PERMISSION` via
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`ANDROID_APP.get().run_on_java_main_thread(...)` (attach `JNIEnv` from
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`vm_as_ptr()`; Activity from `activity_as_ptr()`), then **re-check on
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`MainEvent::Resume`** — the hook is already wired in `src/lib.rs`
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(TODO(M5) marker).
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2. **READ_MEDIA_IMAGES / READ_EXTERNAL_STORAGE**: `requestPermissions` via
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the same JNI route; the bare `NativeActivity` does not forward
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`onRequestPermissionsResult` to native, so either (a) poll
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`checkSelfPermission` after requesting (good enough), or (b) ship a custom
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`NativeActivity` subclass via cargo-apk2 `java_sources = "android/java"`
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(manifest `activity name` points at it) — the proper callback, reusable
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pattern from the eval.
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3. Facts that constrain design (verified in android-activity 0.6.1 source):
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no `NewIntent` event; `poll_events` may only run on the `android_main`
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thread (Slint owns it — don't add a second consumer); `AndroidApp` is
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`Clone` and a clone works from any thread (`run_on_java_main_thread`,
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`vm_as_ptr`, `activity_as_ptr`).
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4. **Source discovery** for photos: start with a plain directory scan of
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`/storage/emulated/0/Pictures` + `DCIM` (works with all-files access,
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emulator-friendly, and it's what makes the app testable without
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MediaStore). MediaStore integration (API-aware, scoped to
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`READ_MEDIA_IMAGES`) is a later refinement if directory scanning proves
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insufficient.
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## 8. Performance targets & measurement
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Targets (emulator is NOT representative for absolute decode times — validate
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on a real device with the aarch64 build):
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- Grid: 60 fps scrolling at 5k+ items; zero full-size decodes on the hot path.
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- First frame: grid of placeholders < 100 ms after launch (metadata from
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sqlite, images async).
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- Thumbnail decode (grid size): < 5 ms off-thread per JPEG (measure with
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`std::time::Instant` logs; zune-jpeg turbo should be well under).
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- Steady-state memory: in-memory thumb cache bounded (~64–128 MB compressed
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bytes on a phone) + Slint's texture memory for visible tiles only.
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- Cold start (emulator, release): compare against the eval baseline
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(Slint sample ≈ 1–2 s; gallery must not regress > 0.5 s).
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**Scroll-FPS measurement (real device, verified 2026-10-27):**
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`dumpsys gfxinfo wow.gmp.gallery` reports **0 frames** for Slint — the
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NativeActivity window renders via its own EGL surface and is not tracked by
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gfxinfo on Android 15 (works for normal View apps). Use SurfaceFlinger's
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per-layer latency instead:
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```bash
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# find the layer name:
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adb shell dumpsys SurfaceFlinger | grep "VRI-wow.gmp.gallery"
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# while scrolling (swipes via `input swipe`): capture 1 s of frame history
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adb shell "dumpsys SurfaceFlinger --latency 'VRI-wow.gmp.gallery/android.app.NativeActivity#<id>'"
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# each line: latch_time display_time … — display_time is the vsync grid.
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# fps = 1e6 / avg(display gap); jank = display gaps > ~25 ms; the latch
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# column shows frame PRODUCTION timing (p95 ~17 ms = on time at 60 Hz).
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```
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Result (Pixel 9 Pro, release aarch64, 8,577 photos, 500 px thumbs):
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sustained **60.0 fps, 0 display hitches** while scrolling, both cold cache
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(production p95 21–25 ms) and warm cache (production avg 16.6 ms). The
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display presents at a 60 Hz vsync grid (Slint requests Default framerate;
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120 Hz is a later polish item, not an M3 acceptance criterion).
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Note: the shimmer `animation-tick()` keeps frames flowing even at rest,
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so latency history is continuous — filter by swiping if you need
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scroll-only frames.
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Test data (M2): generate a synthetic set on the device — a small Rust `bin`
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or Python script that writes N=5,000 JPEGs of varied sizes/orientations into
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`/storage/emulated/0/Pictures/gallery-test/` (include a few HEICs if
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imagepipe works; include rotated EXIF). Reuse it for every perf run.
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Measure with: `adb shell am start -W` (cold start),
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`dumpsys gfxinfo wow.gmp.gallery framestats`, Perfetto trace (GPU + main +
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pool threads), and `logcat` pool timing logs behind a `debug_timing` flag.
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## 9. Milestones
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- **M0 — scaffold (DONE)**: builds (x86_64 + aarch64 toolchain), installs,
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runs on emulator; permission-aware init + Resume hook; build script;
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manifest with permissions; this document.
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- **M1 — metadata (DONE, 2026-10-27)**: `db.rs` + `scan.rs`; background scan
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thread → sqlite → `VecModel` in a `ListView` (paths as text). Acceptance
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verified on emulator: **5002 files in 153 ms**; relaunch `0+ 0~ 0-` in 2 ms;
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mtime-touch → `1~`, delete → `1-`. Status line shows `N files (a+ u~ d–) in X ms`.
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List paint is instant on relaunch: the DB list is shown first
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("N files (cached)"), the background walk then runs and refreshes
|
||
("Updating… N"). First launch streams results into the list in 512-file
|
||
batches while scanning — the UI never waits for the full DB build
|
||
(`walk_stream`). Hidden dirs (`.thumbnails`, …) are skipped.
|
||
Real-device numbers (Pixel-class, 8.5k photos): cold scan ~4.2–5.9 s
|
||
(filesystem metadata cost — the walk is the bottleneck, not sqlite),
|
||
relaunch paint instant, rescan ~4.2 s. Walk parallelism is an M2/M7
|
||
optimization candidate.
|
||
Gotchas hit (also see §6/§12):
|
||
- `slint::Result` / `slint::WindowHandle` **do not exist in 1.18.1** as
|
||
published on crates.io — desktop bin is `fn main() -> Result<(),
|
||
slint::PlatformError>` + `use slint::ComponentHandle;`. (The M0 desktop
|
||
bin never actually compiled; only the Android lib was built. The eval
|
||
sample `slint_app` is broken the same way.)
|
||
- `.slint` modulo is `Math.mod(x, y)`, not `%`.
|
||
- ListView rows: `for path[index] in root.items: …` (`index` is not in
|
||
scope unless named; `parent` = the ListView).
|
||
- `rusqlite(bundled)` needs `CC_<triple>` pointing at NDK clang for
|
||
Android — `scripts/build.sh` now exports them.
|
||
- Android DB path: `EXTERNAL_DATA_DIR` is **not set** by this
|
||
NativeActivity setup and `temp_dir()` = `/data/user/0` (unwritable).
|
||
Use `/storage/emulated/0/Android/data/<pkg>/files`, internal files dir
|
||
fallback (see `db::android_data_dir`).
|
||
- Emulator: grant all-files access once via
|
||
`adb shell appops set wow.gmp.gallery MANAGE_EXTERNAL_STORAGE allow`; it
|
||
survives `adb install -r`.
|
||
- Files pushed with `adb push` are owned by `shell` mode 640 — `chmod 644`
|
||
or the app can't read them.
|
||
- **M2 — thumbnail engine (DONE, 2026-10-27)**: `images.rs` (turbojpeg
|
||
DCT-level shrink decode via 1/2/1/4/1/8 `ScalingFactor`, all 8 EXIF
|
||
orientations as uniform `(x,y)→(dx,dy)` pixel maps, `image::imageops::resize`
|
||
final fit, re-encode to disk cache at q85; PNG via `image`) + `thumb.rs`
|
||
(dispatcher thread round-robining to N=cores/2 workers clamped 2..8,
|
||
unbounded job queue, disk cache `thumbs/{sha1(path|mtime|size|target)}.jpg`
|
||
— target in the key so list-64px and grid-500px coexist; atomic
|
||
`.tmp`→rename; generation counter for cancellation; per-worker sqlite
|
||
connection writes `set_thumb` w/h/orientation/thumb_path) + `lib.rs`
|
||
(process-wide `AppState` in `OnceLock`, 10 Hz drain timer — `Timer` is
|
||
`!Send`, leaked with `std::mem::forget`, scroll-prefetch with 50-row
|
||
margin, `do_prefetch` flag so streaming scan batches don't re-prefetch) +
|
||
`main.slint` (rows carry `image` now).
|
||
*Accept, verified:* 12 unit tests + 5k synthetic engine test (cold fill,
|
||
100% cache warm refill, generation cancel). Release aarch64 APK 9.8 MB.
|
||
**Real device (Pixel 9 Pro, 8577 photos):** cold scan ~5 s with list
|
||
streaming; warm relaunch paints the cached list instantly; thumbnails
|
||
render in every visible row (screenshot-verified); relaunch cache hits
|
||
~100% (255–258 of first 256 jobs); 2 WebP files misnamed `.jpg` fail
|
||
gracefully (logged, row stays empty). Worker log cadence: every 256 jobs.
|
||
*Known transient (unreproducible): the very first aarch64-release install
|
||
rendered a pure-black screen (no drain-timer "painted" logs) until the
|
||
next launch; it did **not** reproduce on the emulator (screen-off launch +
|
||
wake) nor across repeated device launches. Suspected screen-lock / display
|
||
state race on first GL frame. If it recurs: force a window refresh on
|
||
Resume (see §10.7).*
|
||
*Build gotchas hit (also in build.sh comments):*
|
||
- `ANDROID_PLATFORM=android-26` (NDK CMake toolchain) **conflicts** with
|
||
the `android-build` crate (Slint's Java compile) unless `ANDROID_JAR`
|
||
is set explicitly to `platforms/android-35/android.jar`.
|
||
- x86_64 host builds of turbojpeg-sys need `nasm` (`~/.local/bin/nasm`;
|
||
aarch64 does not).
|
||
- `ADB_SERIAL=…` env var picks the device in build.sh (phone + emulator
|
||
are often both attached).
|
||
- build.sh keywords: `debug` (x86_64), `debug-aarch64`, `x86_64`,
|
||
`aarch64`; second arg `no-install` to skip install.
|
||
- **M3 — grid UI (DONE 2026-10-27)**: 3-column `ListView` grid (`GridRow` =
|
||
one list item holding up to 3 square `CellView`s), shimmer placeholder via
|
||
a time-driven `animation-tick()` expression, scroll-driven prefetch
|
||
(`scrolled → on_scroll`), memory-bound retention (cells drop to shimmer
|
||
when they leave the active range; disk cache repaints them in ~10 ms).
|
||
Key fixes along the way (see §6.11–13): `in property` must be assigned
|
||
explicitly in a `for`; cell updates must replace the whole outer row
|
||
(`apply_row_batch`) and are capped at 16 rows/tick to avoid ANR on fast
|
||
scroll; `on_scroll` only re-anchors the active range + submits prefetch
|
||
(no model mutation), all mutation is in the 10 Hz drain timer.
|
||
*Verified (emulator, 150 real JPEGs + 5k stubs): first paint 0.6 s cold;
|
||
warm relaunch from disk cache; 0 ANRs through 16 fast swipes; backlog
|
||
drains to 0 when idle. Verified on Pixel 9 Pro (release aarch64, 8,577
|
||
photos): first screen ~0.7 s cold at 500 px; scroll = sustained 60 fps
|
||
with 0 display hitches (cold and warm cache) — see §8 for the
|
||
measurement method (gfxinfo does NOT track Slint's window).*
|
||
- **M4 — viewer**: tap cell → full decode + overlay; pinch/pan (manual
|
||
math), double-tap zoom; back gesture/button; EXIF orientation correct.
|
||
- **M5 — permissions**: implement `perm.rs` per §7; launch flow when
|
||
un-granted (settings card → open Settings → recheck on Resume); test the
|
||
exact passgo-style flow on a fresh install.
|
||
- **M6 — polish**: dark theme, animations (slide/fade), search/filter
|
||
(name/date), sort; double-tap zoom; battery-friendly (pool idles, no
|
||
busy repaint — Slint is retained, verify with gfxinfo "total frames").
|
||
- **M7 — perf & release**: real-device (aarch64) pass; Perfetto; memory
|
||
bounds; release APK size check (expect ~8–9 MB like the sample);
|
||
consider the 1.19 upgrade (verify pointer-scroll fix first).
|
||
|
||
## 10. Open questions & risks
|
||
|
||
1. **HEIC (RESOLVED for now)**: the real device has 0 HEIC files (9109
|
||
JPEG, 27 PNG), so HEIC is deferred. When needed: add a decoder to
|
||
`images.rs` dispatch (libheif-rs / `image` heic feature / libvips);
|
||
the engine API is decoder-agnostic.
|
||
2. **Slint pointer-scroll `todo!()` panic** (open issue in the Android
|
||
backend at eval time): could fire on trackpad/touch scroll. Test scrolling
|
||
on M3; if it fires, patch locally (the fix is small) or upgrade to 1.19
|
||
when available.
|
||
3. **Max texture size**: full-screen decode of 12 MP+ images (e.g.
|
||
8192 px) may exceed GPU max texture size on some devices — verify on
|
||
M4; fall back to a 2×-max downscale for display.
|
||
4. **Slint license**: royalty-free tier covers proprietary mobile/desktop/
|
||
web; embedded devices excluded — irrelevant for us, but the repo README
|
||
should state the chosen tier (royalty-free) once the app ships.
|
||
5. **Docs drift**: trust the pinned source (`~/prog/android/ui/slint-src`
|
||
@ v1.18.1) over online docs; bump pin + re-verify after any Slint upgrade.
|
||
6. **rusqlite `bundled`** compiles SQLite from source in every target
|
||
(adds ~30–60 s to clean builds) — acceptable; revisit if it hurts.
|
||
7. **Transient black screen (M2 first launch, unreproducible)**: one
|
||
aarch64-release launch rendered pure black with a dead drain timer until
|
||
relaunch; not reproduced on emulator or device since. Candidate fix if it
|
||
recurs: in the `init_with_event_listener` Resume handler, call
|
||
`window.request_redraw()` / check `window.size()` (a 0×0 or stale surface
|
||
after a screen-off start would match the symptoms). Don't add it
|
||
speculatively.
|
||
|
||
## 11. Pointers
|
||
|
||
- Framework eval (full report + raw notes + both sample apps + screenshots):
|
||
`~/prog/android/ui/` — `REPORT.md`, `NOTES.md`, `slint_app/`, `eframe_app/`,
|
||
`slint-src/` (v1.18.1), `egui-src/` (0.37.0).
|
||
- Slint docs (version-sensitive!): https://slint.dev/docs — Android guide:
|
||
`docs/guide/platforms/mobile/android.mdx` in the source tree.
|
||
- `examples/native-gestures`, `demos/` in `slint-src` — reference code for
|
||
gestures, lists, images.
|
||
- passgo (existing Go app using the same all-files-access pattern):
|
||
`~/prog/go/passgo` — its `scripts/build.sh` and manifest handling are a
|
||
proven reference for the permission UX flow.
|
||
- Emulator AVD: `pad_avd` (google_apis x86_64, API 35); start command in §3.
|
||
- Gitea: push target `git+ssh://gitea@git.wow.st/gmp/gallery.git`
|
||
(repo must exist on the server first, like the other gmp/* repos).
|