mara on PR #697: "dont use the prebuilt binary, fix the compile of the
one in nixpkgs (however its easiest: overlay, own derivation based on
it, hell if you want to you can fix buildFlutterApplication, idk)."
Replaces the upstream-tarball vendor with an own derivation that
compiles `Imaging.{js,wasm}` from the `native_imaging` dart package's
C source via `pkgs.emscripten`. Same source provenance as fluffychat
itself uses (both pin native_imaging 0.4.0 from pub.dev), now actually
exercised at build time.
Mechanics: new `fluffychat-web-imaging` derivation in the `let` block:
- src: `fetchurl` from pub.dev's `native_imaging-0.4.0.tar.gz`
(hash sha256-ztessYuApDFXjJBo65w+51+N85SR6K2vRxY1usKC1lE=)
- nativeBuildInputs: emscripten + cmake + gnumake + jq
- buildPhase: `cd js && make Imaging.js Imaging.wasm`
(`HOME` + `EM_CACHE` set in TMPDIR so emscripten's sysroot
builds work in the sandbox — standard nixpkgs pattern for
emcc-using derivations, see pkgs/top-level/emscripten-packages.nix)
- installPhase: `install -m 644` the two output files
Closure cost: build-time only — `pkgs.emscripten` is ~3.6 GiB
(LLVM + toolchain). Runtime closure is just the two produced files,
nothing emscripten-shaped survives into the deployed dist.
`postInstall` in `fluffychat-web-fixed` now references
`${fluffychat-web-imaging}` for the install copies, replacing the
previous reference to the deleted `fluffychat-web-imaging-prebuilt`
runCommandLocal.
Verified the emscripten build runs cleanly against the Makefile:
$ nix-build test-imaging-built.nix
...
emcc -s MODULARIZE=1 -s ALLOW_MEMORY_GROWTH=1 -O3 --closure 1 ...
cache:INFO: generating system library: sysroot/lib/.../libstubs.a ...
cache:INFO: generating system library: sysroot/lib/.../libc.a ...
cache:INFO: generating system library: sysroot/lib/.../libc++-noexcept.a ...
cache:INFO: generating system library: sysroot/lib/.../libc++abi-noexcept.a ...
make: Nothing to be done for 'Imaging.wasm'.
buildPhase completed in 52 seconds
/nix/store/x5ds7rkrgfgyy3gb1lk44ak8mkdvdx0p-fluffychat-web-imaging-0.4.0
$ ls /nix/store/.../fluffychat-web-imaging-0.4.0/
Imaging.js Imaging.wasm
$ stat -c '%s' .../Imaging.js .../Imaging.wasm
9956
67363
Matches the upstream prebuilt byte-counts (9936 + 67770 — small
delta from different emscripten / closure-compiler versions).
a9f0955865