Create a Multi-Threading-Enabled Custom Build

Have a look at this test for a working example.

Start by pulling the latest Docker image with multi-threading support.

docker pull donalffons/opencascade.js:multi-threaded

Next, create a custom build definition. The following will create a full build (based on this one, which is distributed as the NPM package) with multi-threading support.

mainBuild:
  name: customBuild.multi-threaded.js
  # not specifying any bindings will bind everything
  emccFlags:
    # These are just the default values as defined in /src/customBuildSchema.py
    - -O3
    - -sEXPORT_ES6=1
    - -sUSE_ES6_IMPORT_META=0
    - -sEXPORTED_RUNTIME_METHODS=['FS']
    - -sINITIAL_MEMORY=100MB
    - -sMAXIMUM_MEMORY=4GB
    - -sALLOW_MEMORY_GROWTH=1
    - -sUSE_FREETYPE=1
    - -sLLD_REPORT_UNDEFINED
    - --no-entry

    # Currently, the thread pool size has to be defined at compile time, otherwise
    # the execution will hang indefinitely during initialization. The value below
    # will allocate as many threads as there are cpu cores in the system - for
    # the browser. When building a NodeJS application, you might want to use
    # ='require("os").cpus().length' instead.
    - -sPTHREAD_POOL_SIZE='navigator.hardwareConcurrency'

docker run \
  -v "$(pwd):/src" \
  -u "$(id -u):$(id -g)" \
  donalffons/opencascade.js:multi-threaded \
  ./opencascade.full.multi-threaded.yml

This will output 3 files (as opposed to 2 when creating a single-threaded build) into the current folder: opencascade.full.multi-threaded.js, opencascade.full.multi-threaded.wasm and opencascade.full.multi-threaded.worker.js. The web worker will be used for spawning new threads. This file must be accessible at run-time and depending on your bundler and folder structure, you might have to define the file path at which it can be accessed when initializing OpenCascade.js using the optional worker property.

import initOpenCascade from "opencascade.js";
import opencascade from "./openascade.full.js";
import opencascadeWasm from "./openascade.full.wasm";
// When building web-apps, you might want to import the worker to give your bundler a chance to hash the file name.
// import opencascadeWorker from "./openascade.full.worker.js";

initOpenCascade({
  mainJs: opencascade,
  mainWasm: opencascadeWasm,
  worker: "/path/to/opencascade.full.worker.js", // or pass opencascadeWorker (containing a string with the path to the worker)
}).then(oc => {
  // ready to use multi-threaded build
});

That's it - multi-threading should now be enabled.