add parameter to emscripten_set_main_loop to optionally simulate an infinite loop by throwing an exception (like glutMainLoop)

Author: kripken

src/library_browser.js

@@ -402,7 +402,7 @@ mergeInto(LibraryManager.library, {
     }, millis);
   },
 
-  emscripten_set_main_loop: function(func, fps) {
+  emscripten_set_main_loop: function(func, fps, simulateInfiniteLoop) {
     Module['noExitRuntime'] = true;
 
     var jsFunc = FUNCTION_TABLE[func];
@@ -462,6 +462,10 @@ mergeInto(LibraryManager.library, {
       }
     }
     Browser.mainLoop.scheduler();
+
+    if (simulateInfiniteLoop) {
+      throw 'emscripten_set_main_loop simulating infinite loop by throwing so we get right into the JS event loop';
+    }
   },
 
   emscripten_cancel_main_loop: function() {

system/include/emscripten/emscripten.h

@@ -46,14 +46,30 @@ extern void emscripten_async_run_script(const char *script, int millis);
  * code assumes that), so you can break the code up into
  * asynchronous callbacks, but you must pause the main
  * loop until they complete.
+ *
+ * @simulate_infinite_loop If true, this function will throw an
+ *    exception in order to stop execution of the caller. This
+ *    will lead to the main loop being entered instead of code
+ *    after the call to emscripten_set_main_loop being run, which
+ *    is the closest we can get to simulating an infinite loop
+ *    (we do something similar in glutMainLoop in GLUT). If this
+ *    parameter is false, then the behavior is the same as it
+ *    was before this parameter was added to the API, which is
+ *    that execution continues normally. Note that in both cases
+ *    we do not run global destructors, atexit, etc., since we
+ *    know the main loop will still be running, but if we do
+ *    not simulate an infinite loop then the stack will be unwinded.
+ *    That means that if simulate_infinite_loop is false, and
+ *    you created an object on the stack, it will be cleaned up
+ *    before the main loop will be called the first time.
  */
 #if EMSCRIPTEN
-extern void emscripten_set_main_loop(void (*func)(), int fps);
+extern void emscripten_set_main_loop(void (*func)(), int fps, int simulate_infinite_loop);
 extern void emscripten_pause_main_loop();
 extern void emscripten_resume_main_loop();
 extern void emscripten_cancel_main_loop();
 #else
-#define emscripten_set_main_loop(func, fps) \
+#define emscripten_set_main_loop(func, fps, simulateInfiniteLoop) \
   while (1) func();
 #endif
 

tests/emscripten_api_browser.cpp

@@ -53,7 +53,7 @@ void mainey() {
 void four(void *arg) {
   assert((int)arg == 43);
   printf("four!\n");
-  emscripten_set_main_loop(mainey, 0);
+  emscripten_set_main_loop(mainey, 0, 0);
 }
 
 void __attribute__((used)) third() {

tests/emscripten_api_browser_infloop.cpp

@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <string.h>
+#include <emscripten.h>
+
+struct Class {
+  static Class *instance;
+
+  int x;
+
+  Class() : x(0) {}
+
+  void print() {
+    char buf[18];
+    memset(buf, 0, 18); // clear stack. if we did not simulate infinite loop, this clears x and is a bug!
+    x += buf[7];
+
+    printf("waka %d\n", x++);
+
+    if (x == 7) {
+      int result = x;
+      REPORT_RESULT();
+    }
+  }
+
+  static void callback() {
+    instance->print();
+  }
+
+  void start() {
+    instance = this;
+    emscripten_set_main_loop(Class::callback, 3, 1); // important if we simulate an infinite loop here or not
+  }
+};
+
+Class *Class::instance = NULL;
+
+int main() {
+  Class().start();
+  return 1;
+}
+

tests/emscripten_fs_api_browser.cpp

@@ -69,7 +69,7 @@ int main() {
     onLoaded,
     onError);
 
-  emscripten_set_main_loop(wait_wgets, 0);
+  emscripten_set_main_loop(wait_wgets, 0, 0);
 
   return 0;
 }

tests/enet_client.c

@@ -94,7 +94,7 @@ int main (int argc, char ** argv)
                         "console.log('added.');");
 #endif
 
-  emscripten_set_main_loop(main_loop, 1);
+  emscripten_set_main_loop(main_loop, 1, 1);
 
   return 1;
 }

tests/enet_server.c

@@ -92,7 +92,7 @@ int main (int argc, char ** argv)
     exit (EXIT_FAILURE);
   }
 
-  emscripten_set_main_loop(main_loop, 1);
+  emscripten_set_main_loop(main_loop, 1, 1);
 
   return 1;
 }

tests/runner.py

@@ -8664,6 +8664,9 @@ def btest(self, filename, expected=None, reference=None, reference_slack=0, args
     def test_emscripten_api(self):
       self.btest('emscripten_api_browser.cpp', '1')
 
+    def test_emscripten_api_infloop(self):
+      self.btest('emscripten_api_browser_infloop.cpp', '7')
+
     def test_emscripten_fs_api(self):
       shutil.copyfile(path_from_root('tests', 'screenshot.png'), os.path.join(self.get_dir(), 'screenshot.png')) # preloaded *after* run
       self.btest('emscripten_fs_api_browser.cpp', '1')

tests/sdl_canvas_palette_2.c

@@ -68,7 +68,7 @@ int main() {
 
   //Animation
   printf("you should see red gradient animation\n");
-  emscripten_set_main_loop(animatePalette, 0);
+  emscripten_set_main_loop(animatePalette, 0, 1);
 
   SDL_Quit();
 

tests/sdl_mouse.c

@@ -64,6 +64,6 @@ void main_2(void* arg) {
   emscripten_run_script("window.simulateMouseEvent(30, 77, -1)"); // move some more
   emscripten_run_script("window.simulateMouseEvent(30, 77, 1)"); // trigger the end
 
-  emscripten_set_main_loop(one, 0);
+  emscripten_set_main_loop(one, 0, 0);
 }
 

tests/sdl_quit.c

@@ -26,7 +26,7 @@ int main() {
   SDL_Init(SDL_INIT_VIDEO);
   SDL_Surface *screen = SDL_SetVideoMode(600, 450, 32, SDL_HWSURFACE);
 
-  emscripten_set_main_loop(one, 0);
+  emscripten_set_main_loop(one, 0, 0);
 
   emscripten_run_script("setTimeout(function() { window.close() }, 2000)");
 }

tests/websockets.c

@@ -115,7 +115,7 @@ int main(void)
   }
 
 #if EMSCRIPTEN
-  emscripten_set_main_loop(iter, 0);
+  emscripten_set_main_loop(iter, 0, 0);
 #else
   while (!done) iter(NULL);
 #endif

tests/websockets_bi.c

@@ -124,7 +124,7 @@ int main(void)
                         "iframe.src = 'side.html';"
                         "document.body.appendChild(iframe);"
                         "console.log('added.');");
-  emscripten_set_main_loop(iter, 0);
+  emscripten_set_main_loop(iter, 0, 0);
 #else
   while (!done) iter(NULL);
 #endif

tests/websockets_bi_listener.c

@@ -141,7 +141,7 @@ int main(void)
                         "iframe.src = 'side.html';"
                         "document.body.appendChild(iframe);"
                         "console.log('added.');");
-  emscripten_set_main_loop(iter, 0);
+  emscripten_set_main_loop(iter, 0, 0);
 #else
   while (!done) iter(NULL);
 #endif

tests/websockets_gethostbyname.c

@@ -122,7 +122,7 @@ int main(void)
   }
 
 #if EMSCRIPTEN
-  emscripten_set_main_loop(iter, 0);
+  emscripten_set_main_loop(iter, 0, 0);
 #else
   while (!done) iter(NULL);
 #endif