Provide a js fallback when the wasm version of openjpeg is failing to load (bug 1935076)

eslint.config.mjs

@@ -39,6 +39,7 @@ export default [
       "test/tmp/",
       "test/pdfs/",
       "web/locale/",
+      "web/wasm/",
       "**/*~/",
     ],
   },

gulpfile.mjs

@@ -651,10 +651,17 @@ function createStandardFontBundle() {
 
 function createWasmBundle() {
   return ordered([
-    gulp.src(["external/openjpeg/*.wasm", "external/openjpeg/LICENSE_*"], {
-      base: "external/openjpeg",
-      encoding: false,
-    }),
+    gulp.src(
+      [
+        "external/openjpeg/*.wasm",
+        "external/openjpeg/openjpeg_nowasm_fallback.js",
+        "external/openjpeg/LICENSE_*",
+      ],
+      {
+        base: "external/openjpeg",
+        encoding: false,
+      }
+    ),
   ]);
 }
 

src/core/jpx.js

@@ -31,18 +31,44 @@ class JpxImage {
 
   static #modulePromise = null;
 
+  static #hasJSFallback = false;
+
   static #wasmUrl = null;
 
   static setOptions({ handler, wasmUrl }) {
-    if (!this.#buffer) {
-      this.#wasmUrl = wasmUrl || null;
-      if (wasmUrl === null) {
-        this.#handler = handler;
-      }
+    if (this.#buffer || this.#hasJSFallback || this.#modulePromise) {
+      return;
+    }
+    this.#wasmUrl = wasmUrl || null;
+    if (wasmUrl === null) {
+      this.#handler = handler;
     }
   }
 
-  static async #instantiateWasm(imports, successCallback) {
+  static async #getJsModule(fallbackCallback) {
+    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("TESTING")) {
+      this.#wasmUrl ??= "/build/generic/web/wasm/";
+    }
+    const path =
+      typeof PDFJSDev === "undefined"
+        ? `../${this.#wasmUrl}openjpeg_nowasm_fallback.js`
+        : `${this.#wasmUrl}openjpeg_nowasm_fallback.js`;
+
+    let instance = null;
+    try {
+      const mod = await (typeof PDFJSDev === "undefined"
+        ? import(path) // eslint-disable-line no-unsanitized/method
+        : __non_webpack_import__(path));
+      instance = mod.default();
+    } catch (e) {
+      warn(`JpxImage#getJsModule: ${e}`);
+    }
+
+    this.#hasJSFallback = true;
+    fallbackCallback(instance);
+  }
+
+  static async #instantiateWasm(fallbackCallback, imports, successCallback) {
     const filename = "openjpeg.wasm";
     try {
       if (!this.#buffer) {
@@ -57,9 +83,13 @@ class JpxImage {
       }
       const results = await WebAssembly.instantiate(this.#buffer, imports);
       return successCallback(results.instance);
+    } catch (reason) {
+      warn(`JpxImage#instantiateWasm: ${reason}`);
+
+      this.#getJsModule(fallbackCallback);
+      return null;
     } finally {
       this.#handler = null;
-      this.#wasmUrl = null;
     }
   }
 
@@ -67,12 +97,26 @@ class JpxImage {
     bytes,
     { numComponents = 4, isIndexedColormap = false, smaskInData = false } = {}
   ) {
-    this.#modulePromise ||= OpenJPEG({
-      warn,
-      instantiateWasm: this.#instantiateWasm.bind(this),
-    });
-
+    if (!this.#modulePromise) {
+      const { promise, resolve } = Promise.withResolvers();
+      const promises = [promise];
+      if (this.#hasJSFallback) {
+        this.#getJsModule(resolve);
+      } else {
+        promises.push(
+          OpenJPEG({
+            warn,
+            instantiateWasm: this.#instantiateWasm.bind(this, resolve),
+          })
+        );
+      }
+      this.#modulePromise = Promise.race(promises);
+    }
     const module = await this.#modulePromise;
+
+    if (!module) {
+      throw new JpxError("OpenJPEG failed to initialize");
+    }
     let ptr;
 
     try {

test/driver.js

@@ -638,7 +638,7 @@ class Driver {
           password: task.password,
           cMapUrl: CMAP_URL,
           standardFontDataUrl: STANDARD_FONT_DATA_URL,
-          wasmUrl: WASM_URL,
+          wasmUrl: task.noWasm ? null : WASM_URL,
           disableAutoFetch: !task.enableAutoFetch,
           pdfBug: true,
           useSystemFonts: task.useSystemFonts,

test/test_manifest.json

@@ -6411,6 +6411,14 @@
     "rounds": 1,
     "type": "eq"
   },
+  {
+    "id": "issue19326_nowasm",
+    "file": "pdfs/issue19326.pdf",
+    "md5": "b4d937017daf439a6318501428e0c6ba",
+    "noWasm": true,
+    "rounds": 1,
+    "type": "eq"
+  },
   {
     "id": "issue19326_main_thread_fetch",
     "file": "pdfs/issue19326.pdf",