Offload rendering to a worker

gulpfile.mjs

@@ -589,6 +589,18 @@ function createWorkerBundle(defines) {
     .pipe(webpack2Stream(workerFileConfig));
 }
 
+function createRendererWorkerBundle(defines) {
+  const rendererWorkerFileConfig = createWebpackConfig(defines, {
+    filename: defines.MINIFIED ? "pdf.renderer.min.mjs" : "pdf.renderer.mjs",
+    library: {
+      type: "module",
+    },
+  });
+  return gulp
+    .src("./src/pdf.renderer.js", { encoding: false })
+    .pipe(webpack2Stream(rendererWorkerFileConfig));
+}
+
 function createWebBundle(defines, options) {
   const viewerFileConfig = createWebpackConfig(
     defines,
@@ -1103,6 +1115,7 @@ function buildGeneric(defines, dir) {
   return ordered([
     createMainBundle(defines).pipe(gulp.dest(dir + "build")),
     createWorkerBundle(defines).pipe(gulp.dest(dir + "build")),
+    createRendererWorkerBundle(defines).pipe(gulp.dest(dir + "build")),
     createSandboxBundle(defines).pipe(gulp.dest(dir + "build")),
     createWebBundle(defines, {
       defaultPreferencesDir: defines.SKIP_BABEL
@@ -1294,6 +1307,7 @@ function buildMinified(defines, dir) {
   return ordered([
     createMainBundle(defines).pipe(gulp.dest(dir + "build")),
     createWorkerBundle(defines).pipe(gulp.dest(dir + "build")),
+    createRendererWorkerBundle(defines).pipe(gulp.dest(dir + "build")),
     createSandboxBundle(defines).pipe(gulp.dest(dir + "build")),
     createImageDecodersBundle({ ...defines, IMAGE_DECODERS: true }).pipe(
       gulp.dest(dir + "image_decoders")
@@ -1439,6 +1453,9 @@ gulp.task(
         createWorkerBundle(defines).pipe(
           gulp.dest(MOZCENTRAL_CONTENT_DIR + "build")
         ),
+        createRendererWorkerBundle(defines).pipe(
+          gulp.dest(MOZCENTRAL_CONTENT_DIR + "build")
+        ),
         createWebBundle(defines, { defaultPreferencesDir: "mozcentral/" }).pipe(
           gulp.dest(MOZCENTRAL_CONTENT_DIR + "web")
         ),
@@ -1536,6 +1553,9 @@ gulp.task(
         createWorkerBundle(defines).pipe(
           gulp.dest(CHROME_BUILD_CONTENT_DIR + "build")
         ),
+        createRendererWorkerBundle(defines).pipe(
+          gulp.dest(CHROME_BUILD_CONTENT_DIR + "build")
+        ),
         createSandboxBundle(defines).pipe(
           gulp.dest(CHROME_BUILD_CONTENT_DIR + "build")
         ),

src/core/document.js

@@ -438,6 +438,7 @@ class Page {
 
   async getOperatorList({
     handler,
+    rendererHandler,
     sink,
     task,
     intent,

src/core/evaluator.js

@@ -787,7 +787,7 @@ class PartialEvaluator {
       // globally, check if the image is still cached locally on the main-thread
       // to avoid having to re-parse the image (since that can be slow).
       if (w * h > 250000 || hasMask) {
-        const localLength = await this.handler.sendWithPromise("commonobj", [
+        const localLength = await this.sendWithPromise("commonobj", [
           objId,
           "CopyLocalImage",
           { imageRef },

src/core/worker.js

@@ -82,6 +82,8 @@ class WorkerMessageHandler {
 
   static setup(handler, port) {
     let testMessageProcessed = false;
+    let rendererHandler = null;
+
     handler.on("test", data => {
       if (testMessageProcessed) {
         return; // we already processed 'test' message once
@@ -94,12 +96,19 @@ class WorkerMessageHandler {
 
     handler.on("configure", data => {
       setVerbosityLevel(data.verbosity);
+      rendererHandler = new MessageHandler(
+        "worker-channel",
+        "renderer-channel",
+        data.channelPort
+      );
     });
 
-    handler.on("GetDocRequest", data => this.createDocumentHandler(data, port));
+    handler.on("GetDocRequest", data =>
+      this.createDocumentHandler(data, port, rendererHandler)
+    );
   }
 
-  static createDocumentHandler(docParams, port) {
+  static createDocumentHandler(docParams, port, rendererHandler) {
     // This context is actually holds references on pdfManager and handler,
     // until the latter is destroyed.
     let pdfManager;
@@ -173,7 +182,11 @@ class WorkerMessageHandler {
         const task = new WorkerTask("loadXfaResources");
         startWorkerTask(task);
 
-        await pdfManager.ensureDoc("loadXfaResources", [handler, task]);
+        await pdfManager.ensureDoc("loadXfaResources", [
+          handler,
+          task,
+          rendererHandler,
+        ]);
         finishWorkerTask(task);
       }
 
@@ -776,6 +789,7 @@ class WorkerMessageHandler {
         page
           .getOperatorList({
             handler,
+            rendererHandler,
             sink,
             task,
             intent: data.intent,
@@ -863,6 +877,10 @@ class WorkerMessageHandler {
       return pdfManager.fontFallback(data.id, handler);
     });
 
+    rendererHandler.on("FontFallback", function (data) {
+      return pdfManager.fontFallback(data.id, rendererHandler);
+    });
+
     handler.on("Cleanup", function (data) {
       return pdfManager.cleanup(/* manuallyTriggered = */ true);
     });