[leonardomag31-lab]

Why

labelle-bgfx#168 plays a bundled music file on Android: it decodes the APK asset with video.decodeTrack, which reads a file descriptor. To get that fd, the PR declared the AAsset* externs in bgfx and read ANativeActivity.assetManager by a hand-counted index (fields[8]). @apotema's review asked for that to live here instead: Android code goes in labelle-android, bgfx only gets generic seams (the rule from labelle-bgfx#172).

What

• assets.openFd(activity, name) ?AssetFd: opens name (relative to the APK's assets/) and returns { fd, start, len } for the fd decoders here (video.decodeTrack, video.VideoDecoder). AssetFd.close() closes the descriptor; the caller owns it.
  • Null for a null activity, an empty name, a name over 255 bytes, a missing or compressed asset, and always off Android.
  • Callable from any thread (bgfx calls it from its decode worker): the NDK's AAssetManager is thread-safe and the AAsset lives only inside the call.
• src/jni/asset_fd.c: reads activity->assetManager by name through <android/native_activity.h>, then does AAssetManager_open → AAsset_openFileDescriptor64 → AAsset_close (the fd is dup'd, so it outlives the AAsset). Same shape as the other jni/*.c files.
• root.zig exports assets; build.zig compiles the C file.

The asset must be stored uncompressed in the APK, which the android provider already does.

Tests

• zig build test: host 133/133. The 5 new tests:
  • null off Android
  • the name reaches the JNI half NUL-terminated, and the fd and range come back
  • a failed open is null
  • null activity / empty / over-long names never reach the JNI half, and the 255-byte boundary is accepted
  • openFd analyses on every target: takes openFd's address so the Android compile-check type-checks the JNI branch. That branch was only reached lazily before, which let a calling-convention mismatch through that the first device build caught. I checked that the check fails if the mismatch comes back.
• ANDROID_NDK_HOME=… zig build test -Dtarget=aarch64-linux-android: compiles.
• On device (P42, Android 16): Flying Platform #976 built against this branch (local: pin) and the reworked labelle-bgfx#168. The in-game theme MP3 opens through openFd and decodes to exactly 5,375,040 frames (the same as the old path), gameplay runs at 52 FPS, and the theme plays.

Next

Release (v0.4.1) → labelle-bgfx#168 bumps its labelle-android pin to it (the same line #186 moves to 0.4.0) → bgfx release → FP #976's pin.

Not in scope: labelle-bgfx's src/video/backend.zig has the same hand-rolled asset open; moving it onto openFd is the follow-up @apotema mentioned.

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[apotema]

Approved. This is exactly the seam the #168 review asked for (reviewed at ff6f338; Claude, on Alexandre's behalf).

• jni/asset_fd.c: reads assetManager through <android/native_activity.h>, so there's no more hand-counted fields[8]. The AAsset is closed after AAsset_openFileDescriptor64, so the caller owns only the dup'd fd. A compressed entry gives -1, as documented.
• assets.zig: the name checks are split from the JNI half, so host tests cover NUL-termination, the 255-byte boundary, and null/empty/over-long names never reaching JNI. _ = &openFd makes the Android compile-check analyse the JNI branch. The thread-safety note is right: AAssetManager is thread-safe, and the asset is opened and closed in one call.
• CI: all 9 checks green.

Before merging:

1. Merge main: the branch is 1 behind; main has since released 0.5.0, the Vulkan auto default.
2. Release as v0.6.0, not v0.4.1: 0.5.0 already shipped, and this adds public API. Bump build.zig.zon to 0.6.0 in this PR or a release PR, then tag v0.6.0.
3. Add a labelle-registry entry for 0.6.0 (commit + sha256 of the commit tarball, as in #12/#13), or FP's provider lock can't resolve it.