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  "slug": "webgl-multithreading-issues",
  "title": "关于多线程问题",
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    "name": "Perrin Yong",
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    },
    {
      "depth": 3,
      "text": "1. 浏览器端：真·多线程 WebGL + WASM",
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      "text": "2. 微信 / 抖音小程序：只有「逻辑线程」，没有「共享内存」",
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  "contentMarkdown": "# 关于多线程问题\n\n# 关于多线程问题\n\n\n| 场景          | WebGL 渲染线程                                                                       | C++/WASM 多线程                                                                                            | 说明                                                                       |\n| ----------- | -------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------ |\n| 桌面／移动浏览器    | **支持**：使用 `Web Worker + OffscreenCanvas` 渲染线程、`SharedArrayBuffer` & WASM Threads | **支持**：`emcc -s USE_PTHREADS=1 …` 生成 pthreads-WASM，浏览器把每个 `std::thread` 映射到 Worker                      | 需启用 COOP/COEP 响应头以开放 SharedArrayBuffer([caniuse.com][1], [juejin.cn][2]) |\n| 微信小程序       | JS Worker & `wx.createOffscreenCanvas()` 可用，但 **仅 2D / 部分 WebGL**                | **不支持**：运行环境禁用了 SharedArrayBuffer，无法启用 WASM Threads([developer.open-douyin.com][3], [blog.csdn.net][4]) |                                                                          |\n| 抖音/飞书/字节小游戏 | `tt.createCanvas()` 第二次返回 OffscreenCanvas，可在 Worker 内绘制 WebGL，但仍是 **单工内存**       | **不支持**：与微信相同，没有跨源隔离 API，可用 JS Worker 分工渲染([developer.open-douyin.com][3])                              |                                                                          |\n\n### 1. 浏览器端：真·多线程 WebGL + WASM\n\n1. **开启浏览器线程能力**\n\n```bash\nemcc main.cpp \\\n\t-sUSE_PTHREADS=1           # 打开 pthreads → WASM Threads\n\t-sPTHREAD_POOL_SIZE=8      # 预建 8 个 Worker\n\t-sOFFSCREENCANVAS_SUPPORT=1\\\n\t-sPROXY_TO_PTHREAD=1       # 把主线程逻辑也放到 Worker\n\t-O3 -o index.html\n```\n\n2. **服务器需送两头**（缺一不可）\n\n```yaml\nCross-Origin-Opener-Policy: same-origin\nCross-Origin-Embedder-Policy: require-corp\n```\n\n   这样浏览器会解锁 `SharedArrayBuffer`，WASM Threads 就能共享线性内存。\n\n3. **典型线程代码**\n\n```cpp\n#include <thread>\nvoid worker(int id){ /* heavy job */ }\nint main(){\n   std::thread t(worker, 0);\n   t.join();\n   return 0;\n}\n```\n\n每条 `std::thread` 会被 Emscripten 映射成一个 JavaScript Worker，渲染可通过 `emscripten_set_canvas_element_size` 或 `eglMakeCurrent` 与 OffscreenCanvas 交互。\n\n---\n\n### 2. 微信 / 抖音小程序：只有「逻辑线程」，没有「共享内存」\n\n微信不支持wasm层面启用多线程。\nWorker框架多线程文档： https://developers.weixin.qq.com/minigame/dev/guide/framework/worker/tutorial.html\n\n[1]: https://caniuse.com/wasm-threads?utm_source=chatgpt.com \"WebAssembly Threads and Atomics | Can I use... Support tables for HTML5 ...\"\n[2]: https://juejin.cn/post/7508968054875308043?utm_source=chatgpt.com \"Web Worker + OffscreenCanvas，实现真正多线程渲染体验\"\n[3]: https://developer.open-douyin.com/forum/question/post/66d72de7372f131f6bd89b76 \"〖提问〗小游戏中OffscreenCanvas正确的使用姿势应该是怎样？ - 抖音开放平台\"\n[4]: https://blog.csdn.net/weixin_44892327/article/details/135712532 \"微信小程序 页面跳转失败 SharedArrayBuffer will require cross-origin isolation as of M92, around July 2021. See-CSDN博客\"\n"
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