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punktfunk/clients/android
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refactor(haptics): one copy of each thing every rumble path was transcribing
Twelve findings from the sweep's DRY/docs/dead-code tail. Most are small; three found
real defects hiding behind the duplication.

**The UHID event ABI existed five times.** Every UHID gamepad backend — DualSense,
DualShock 4, Switch Pro, Steam Controller, Steam Controller 2 — carried its own verbatim
copy of the kernel's constants plus its own `put_cstr`, and they had already drifted:
`switch_pro` was missing the SET_REPORT pair entirely, and `steam_controller` read a
FIXED 16-byte SET_REPORT window instead of the event's own `size`. That last one is a
bug in both directions — a longer report was truncated, and a shorter one had the parser
reading whatever the reused event buffer still held past the payload, i.e. acting on
rumble values the game never wrote. Now one `uhid_abi` module owns the numbers plus the
two accessors that are easy to get subtly wrong, with tests on exactly that.

**A dead force-feedback id fallback.** ff-core's `input_ff_upload` picks a free effect
slot and writes it into the effect BEFORE uinput forwards the request, so the `id == -1`
branch could never run — and allocating from a local counter would have been the wrong
answer anyway, since the kernel owns that id space. Removed, with a `debug_assert` where
it stood.

**Apple's HID path silently dropped weak rumble.** `hidByte` took the top byte with no
non-zero floor, so every amplitude below 0x0100 rendered as exactly nothing. Android has
always floored it at 1; this was the odd one out. That converter also existed twice
byte-identically inside one Gradle module — now one `wireAmplitudeToByte`.

Also: the DS5 output-report layout gets named offsets (`dualsense_proto::out_report`)
documenting all three transport bases — USB 0, SDL payload −1, Bluetooth +2 — since the
differing bases are transport-forced, not drift. `pf-client-core` cannot import them (it
and `pf-inject` do not depend on each other, and a DualSense layout has no business in
`punktfunk-core`, their only shared crate), so its copy now DERIVES its offsets by
explicit subtraction and a test pins the relationship. `PUNKTFUNK_HID_EFFECT_MAX` sizes
the struct it describes instead of a second literal 11 — the header now emits
`uint8_t effect[PUNKTFUNK_HID_EFFECT_MAX]`. The rumble policy engine's `min_pulse_ms`
and `keepalive_ms` docs stop naming cases nothing implements: no in-tree caller sets
`min_pulse_ms`, and the macOS DualSense-over-BT keepalive the doc cited CANNOT be served
by the quirk, because that renderer skips writes whose levels are unchanged and would
swallow the engine's re-emit — it keeps its own keepalive instead. `TrackpadHaptic` is
marked as staged scaffolding (the tag is on a shipped wire; removing the variant would
not reclaim it). Three ×257-vs-`<<8` doc comments corrected — the scaling itself is fine,
both round-trip to 255. `backstop_ms.max(160)` deleted as unreachable (the engine floors
at 500). New tests for `Ds5Feedback` and for the Android rumble JNI packing on BOTH sides,
with `MAX_PADS <= 16` now a compile-time assertion rather than a comment.

Closes S1-S9, S11, T2, T3 (design/haptics-sweep-2026-08-03.md M12).

S11's second half is NOT a defect and was left alone: `clients/session/src/main.rs`
calls `set_forwarding` unconditionally on every params-build (its own comment explains
why — browse mode reuses one service across launches), so `Ctl::Forwarding` routinely
arrives unchanged and that early-out is what stops a redundant `sync_open` + Valve-HIDAPI
cycle each launch.

Verified: pf-inject clippy -D warnings 0 / 91 tests; pf-client-core + punktfunk-core
clippy 0 / 437 tests (amd64 container); punktfunk-client-android 7 tests; Android :kit:
6 tests; Apple swift build + 189 tests / 0 failures; cargo fmt --all --check clean. Each
new test probed by reverting its fix — the fixed SET_REPORT window fails 3, a broken pack
shift fails 3, dropping the amplitude floor fails 1, and a wrong DS5 offset either fails
the pin or refuses to compile.
2026-08-04 22:52:38 +02:00
..

punktfunk — Android client (phone & TV)

The native Android app for streaming a punktfunk host to your phone, tablet, or Android TV. A Compose app that finds hosts on your network, pairs with a PIN, and streams at the display's own resolution — with hardware HEVC decode, HDR10, and controller support, built for both touch and the couch (D-pad / gamepad focus navigation).

Features

  • Hardware decode — NDK AMediaCodec HEVC → SurfaceView, including HDR10 (Main10 / BT.2020 PQ), with low-latency tuning and a live stats HUD.
  • Audio both ways — Opus + AAudio playback with a jitter ring, plus mic uplink to the host.
  • Controller support — buttons + axes with rumble and HID feedback (lightbar / adaptive triggers); D-pad / gamepad focus navigation for TV and phone.
  • Find hosts automatically — native mDNS discovery; first connect does a one-time SPAKE2 PIN pairing (or TOFU on trusted LANs), then reconnects on a Keystore-wrapped, pinned identity.
  • Compose UI — Connect / Settings / Stream screens with Material You theming.

Built for arm64-v8a + armeabi-v7a + x86_64 — the 32-bit armeabi-v7a slice is what keeps the app installable on the many 32-bit Google TV / Android TV streamers (Walmart onn. 4K, Chromecast with Google TV, budget Amlogic boxes) that otherwise reject a 64-bit-only build as "not compatible".

Get it

Published to Google Play (Internal Testing) — join the beta via the Discord. Per-device setup and pairing: docs.punktfunk.unom.io/docs/install-client.

How it's built — Rust-heavy

Kotlin can't import the cbindgen C header the way Swift can, so a native bridge is unavoidable. We write it in Rust and link punktfunk-core directly — so the Android client reuses the Linux client's orchestration (audio jitter ring, VK keymap inverse, latency/skew math, capture state machine, trust logic) instead of re-porting it into Kotlin.

Side Owns
Rust (native/libpunktfunk_android.so) the JNI seam, NativeClient (QUIC control + UDP data plane), AnnexB → AMediaCodec decode (incl. HDR10), Opus + AAudio audio + mic, controller feedback, latency math, trust/pairing, mdns-sd discovery
Kotlin (app/, kit/) Compose UI, SurfaceView lifecycle, input capture, the Wi-Fi MulticastLock + permission UX, Keystore identity

The single seam is io.unom.punktfunk.kit.NativeBridgeJava_io_unom_punktfunk_kit_NativeBridge_*.

native/           Rust cdylib (workspace member) — links punktfunk-core directly
  src/lib.rs        crate doc · JNI_OnLoad · version probes
  src/session/      session lifecycle: connect/pair + trust, plane start/stop, input shims
  src/decode.rs     AnnexB → AMediaCodec HEVC hardware decode → SurfaceView (incl. HDR10)
  src/audio.rs · src/mic.rs   Opus + AAudio playback / mic uplink
  src/feedback.rs · src/stats.rs   rumble + HID feedback; live video stats
  src/discovery.rs  native mdns-sd browse of the host's _punktfunk._udp advert
app/              :app — Compose UI: Connect / Settings / Stream (phone + TV)
kit/              :kit — NativeBridge · native mDNS discovery · Gamepad · Keymap · Keystore identity

Build & run

Prerequisites: Android SDK + NDK r30 (30.0.14904198), platforms;android-37.0, build-tools;37.0.0, cmake;3.22.1 (builds libopus); JDK 21 (AGP 9.2 runs on JDK 1721, not a newer default); Rust with rustup target add aarch64-linux-android armv7-linux-androideabi x86_64-linux-android and cargo install cargo-ndk. Toolchain is pinned (AGP 9.2 · Gradle 9.4.1 · Kotlin 2.3.21 · Compose BOM 2026.05.01 · compileSdk 37 · minSdk 28).

Android Studio: open clients/android — it uses its bundled JBR 21, and the cargoNdk* task builds the .so as part of the normal build.

CLI (point Gradle at JDK 21 if your machine default is newer):

export JAVA_HOME="$(/usr/libexec/java_home -v 21)"   # or your Temurin 21 path
cd clients/android
./gradlew :app:assembleDebug     # cargo-ndk cross-compiles libpunktfunk_android.so first
./gradlew :app:installDebug      # onto a running emulator/device
# emulators from env setup:  emulator -avd pf_phone   |   emulator -avd pf_tv

The debug APK lands in app/build/outputs/apk/debug/. Launch it, pick a host, pair, and stream.