loadWorkerViaBlob workaround for loading workers cross-origin

Author: Birch-san

box2d3-wasm/.gitignore

@@ -1,6 +1,6 @@
 /cmake-build*/
 /build/*
-!/build/*.template.d.ts
+!/build/*.template.*
 !/build/dist/
 /build/dist/es/*
 !/build/dist/es/entry.mjs

box2d3-wasm/build/Box2D.template.d.ts

@@ -21,6 +21,10 @@ export interface OurModuleOptions {
   // some browsers (e.g. Safari <16.4) cannot grow shared memory, so turning this off
   // could improve compatibility in that situation.
   sharedMemEnabled: boolean;
+  // default: false
+  // enable this if you're disallowed from loading workers cross-origin but allowed to download assets cross-origin.
+  // we will fetch the worker asset, turn it into a blob and create a worker from the blob.
+  loadWorkerViaBlob: boolean;
 }
 
 // Combine known options with arbitrary properties

box2d3-wasm/build/allocate-unused-worker.template.mjs

@@ -0,0 +1,36 @@
+  allocateUnusedWorkerViaBlob: async function() {
+    if (!globalThis._workerPromise) {
+      globalThis._workerPromise = (async function() {
+        const response = await fetch(new URL("Box2D.deluxe.mjs", import.meta.url));
+        const text = await response.text();
+        const blob = new Blob([text], { type: 'application/javascript' });
+        const workerUrl = URL.createObjectURL(blob);
+
+        setTimeout(() => {
+          URL.revokeObjectURL(workerUrl);
+          delete globalThis._workerPromise;
+        }, 0);
+
+        return workerUrl;
+      })();
+    }
+
+    const workerUrl = await globalThis._workerPromise;
+
+    var workerOptions = {
+      "type": "module",
+      "workerData": "em-pthread",
+      "name": "em-pthread-" + PThread.nextWorkerID
+    };
+
+    const worker = new Worker(workerUrl, workerOptions);
+    PThread.unusedWorkers.push(worker);
+    return worker;
+  },
+  allocateUnusedWorker: async function() {
+    if (loadWorkerViaBlob) {
+      await PThread.allocateUnusedWorkerViaBlob();
+    } else {
+      PThread.allocateUnusedWorkerDirect();
+    }
+  },

box2d3-wasm/build/module-arg.template.mjs

@@ -0,0 +1,7 @@
+  moduleArg = {
+    pthreadCount: globalThis.navigator?.hardwareConcurrency ?? 4,
+    sharedMemEnabled: true,
+    loadWorkerViaBlob: false,
+    ...moduleArg,
+  };
+  const {pthreadCount, sharedMemEnabled, loadWorkerViaBlob} = moduleArg;

box2d3-wasm/shell/1_build_wasm.sh

@@ -159,7 +159,10 @@ case "$FLAVOUR" in
     # all of our text replacements are just for disabling/tuning deluxe functionality. compat flavour doesn't need any text replacements.
     ;;
   deluxe)
-    awk -f "$DIR/modify_emscripten_mjs.$FLAVOUR.awk" "$ES_PRECURSOR" > "$ES_FILE"
+    awk -f "$DIR/modify_emscripten_mjs.$FLAVOUR.awk" \
+    -v module_arg_template="$BUILD_DIR/module-arg.template.mjs" \
+    -v allocate_unused_worker_template="$BUILD_DIR/allocate-unused-worker.template.mjs" \
+    "$ES_PRECURSOR" > "$ES_FILE"
     ;;
 esac
 awk -f "$DIR/modify_emscripten_dts.awk" -v template="$BUILD_DIR/Box2D.template.d.ts" "$ES_TSD_PRECURSOR" > "$ES_TSD"

box2d3-wasm/shell/modify_emscripten_mjs.deluxe.awk

@@ -1,10 +1,12 @@
 #!/usr/bin/env awk -f
 
-BEGIN { found1=0; found2=0; found3=0; found4=0 }
+BEGIN { found1=0; found2=0; found3=0; found4=0; found5=0 }
 !found1 && $0 ~ /^async function\(moduleArg = \{\}\) \{$/ {
   print $0
-  print "  moduleArg = {pthreadCount: globalThis.navigator?.hardwareConcurrency ?? 4, sharedMemEnabled:true, ...moduleArg};"
-  print "  const {pthreadCount, sharedMemEnabled} = moduleArg;"
+  while ((getline line < module_arg_template) > 0) {
+    print line
+  }
+  close(module_arg_template)
   found1=1
   next
 }
@@ -25,5 +27,15 @@ BEGIN { found1=0; found2=0; found3=0; found4=0 }
   found4=1
   next
 }
+!found5 && /^[[:space:]]*allocateUnusedWorker\(\) \{$/ {
+  while ((getline line < allocate_unused_worker_template) > 0) {
+    print line
+  }
+  close(allocate_unused_worker_template)
+  sub(/allocateUnusedWorker/, "allocateUnusedWorkerDirect")
+  print
+  found5=1
+  next
+}
 { print }
 END { exit !(found1 && found2 && found3 && found4) }