Fix web: don't spawn the deferred-pause std::thread on web (Aborted() in initEngine)

[felixmin]

Description

On web, SoLoud.init() aborts with RuntimeError: Aborted() inside initEngine as soon as the engine initializes — a regression in 4.0.10.

4.0.10 (#486) starts a background pause-scheduler thread in Player::init() (startPauseEngineScheduler() → std::thread). The web build is single-threaded (web/compile_wasm.sh passes no -pthread), so constructing std::thread calls pthread_create with no thread runtime and the module aborts on the first init(). 4.0.9 had no such thread.

This guards the thread behind __EMSCRIPTEN__:

• startPauseEngineScheduler() / stopPauseEngineScheduler() are no-ops on web (no std::thread is constructed).
• pauseEngine() falls back to the pre-4.0.10 immediate pause on web — the browser's AudioContext doesn't have the OS audio-session settling issue that motivates the delay on native.

Native (iOS/Android/desktop) keeps the deferred, coalesced pause unchanged.

The web artifacts (web/libflutter_soloud_plugin.{js,wasm}) are regenerated via web/compile_wasm.sh (Emscripten 6.0.0, with Opus/Ogg) and committed.

Verified in Chrome with the rebuilt artifacts by calling initEngine:

• published 4.0.10 → Aborted(). Build with -sASSERTIONS for more info. (the crash)
• this branch → initEngine returns 0, isInited() returns 1 — no abort

Note: the wasm here was built with emsdk 6.0.0. If you release with a different Emscripten version, regenerating with yours will keep the committed binary aligned with your toolchain — happy to update if you prefer.

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[felixmin]

Runtime verification (real browser)

I rebuilt the web wasm from this branch with Emscripten 6.0.0 and ran initEngine directly in Chrome, comparing it against the published 4.0.10 artifacts. Minimal harness: load the module factory, then Module.ccall('initEngine', 'number', ['number','number','number','number'], [-1, 44100, 2048, 2]).

Build	Result
4.0.10 (published web/libflutter_soloud_plugin.*)	Aborted(). Build with -sASSERTIONS for more info. — i.e. the reported crash, reproduced
This branch (rebuilt wasm)	initEngine returns 0 (noError), isInited() returns 1 — no abort

So the __EMSCRIPTEN__ guard resolves the web init crash. (The patched test build was compiled without the Xiph/opus libs for speed, but that's irrelevant to this code path — the abort is solely the std::thread constructed in Player::init(), which the guard removes on web.)

Still source-only here — the committed web/libflutter_soloud_plugin.{js,wasm} should be regenerated with your pinned Emscripten toolchain so the artifact diff matches your setup. Happy to push a rebuild if you share the emsdk version you release with.

[alnitak]

Thank you so much! LGTM.

Happy to push a rebuild if you share the emsdk version you release with.

Thanks, I will rebuild wasm before publishing on pub.dev.