support --proxy-to-worker with js target, emitting 2 files for client and worker

emcc

@@ -503,8 +503,13 @@ Options that are modified or new in %s include:
                            to hide these warnings and acknowledge that the
                            explicit use of absolute paths is intentional.
 
-  --proxy-to-worker        Generates both html and js files. The main
-                           program is in js, and the html proxies to/from it.
+  --proxy-to-worker        Runs the main application code in a worker, proxying
+                           events to it and output from it.
+                           If emitting htmlL, this emits an html and a js file,
+                           with the js to be run in a worker. If emitting
+                           js, the target filename contains the part to be run
+                           on the main thread, while a second js file with
+                           suffix ".worker.js" will contain the worker portion.
 
   --emrun                  Enables the generated output to be aware of the
                            emrun command line tool. This allows stdout, stderr
@@ -1977,7 +1982,12 @@ try {
       split_javascript_file(final, unsuffixed(target), split_js_file)
     else:
       if debug_level >= 4: generate_source_map(target)
-      # copy final JS to output
+      if proxy_to_worker:
+        worker_target_basename = target_basename + '.worker'
+        open(target, 'w').write(open(shared.path_from_root('src', 'webGLClient.js')).read() + '\n' + open(shared.path_from_root('src', 'proxyClient.js')).read().replace('{{{ filename }}}', worker_target_basename))
+        shutil.move(final, target[:-3] + '.worker.js')
+      else:
+        # copy final JS to output normally
         shutil.move(final, target)
 
   log_time('final emitting')

tests/test_browser.py

@@ -746,6 +746,13 @@ window.close = function() {
   def test_glgears_proxy(self):
     self.btest('hello_world_gles_proxy.c', reference='gears.png', args=['--proxy-to-worker', '-s', 'GL_TESTING=1'], manual_reference=True, post_build=self.post_manual_reftest)
 
+  def test_glgears_proxy_jstarget(self):
+    # test .js target with --proxy-worker; emits 2 js files, client and worker
+    Popen([PYTHON, EMCC, path_from_root('tests', 'hello_world_gles_proxy.c'), '-o', 'test.js', '--proxy-to-worker', '-s', 'GL_TESTING=1']).communicate()
+    open('test.html', 'w').write(open(path_from_root('src', 'shell_minimal.html')).read().replace('{{{ SCRIPT }}}', '<script src="test.js"></script>'))
+    self.post_manual_reftest()
+    self.run_browser('test.html', None, '/report_result?0')
+
   def test_sdl_canvas_alpha(self):
     self.btest('sdl_canvas_alpha.c', reference='sdl_canvas_alpha.png', reference_slack=9)