emscripten_pause_main_loop and resume

3 files changed, 46 insertions, 15 deletions

diff --git a/src/library_browser.js b/src/library_browser.js
index 1102acbe..07641aed 100644
--- a/src/library_browser.js
+++ b/src/library_browser.js
@@ -5,6 +5,10 @@
 mergeInto(LibraryManager.library, {
   $Browser__postset: 'Module["requestFullScreen"] = function() { Browser.requestFullScreen() };\n', // export requestFullScreen
   $Browser: {
+    mainLoop: {
+      scheduler: null,
+      paused: false
+    },
     pointerLock: false,
     moduleContextCreatedCallbacks: [],
 
@@ -148,28 +152,36 @@ mergeInto(LibraryManager.library, {
   emscripten_set_main_loop: function(func, fps) {
     Module['noExitRuntime'] = true;
 
-    _emscripten_set_main_loop.cancel = false;
     var jsFunc = FUNCTION_TABLE[func];
-
+    var wrapper = function() {
+      if (Browser.mainLoop.paused) return;
+      jsFunc();
+      Browser.mainLoop.scheduler();
+    }
     if (fps && fps > 0) {
-      function doOne() {
-        if (_emscripten_set_main_loop.cancel) return;
-        jsFunc();
-        setTimeout(doOne, 1000/fps); // doing this each time means that on exception, we stop
+      Browser.mainLoop.scheduler = function() {
+        setTimeout(wrapper, 1000/fps); // doing this each time means that on exception, we stop
       }
-      setTimeout(doOne, 1000/fps);
     } else {
-      function doOneRAF() {
-        if (_emscripten_set_main_loop.cancel) return;
-        jsFunc();
-        Browser.requestAnimationFrame(doOneRAF);
+      Browser.mainLoop.scheduler = function() {
+        Browser.requestAnimationFrame(wrapper);
       }
-      Browser.requestAnimationFrame(doOneRAF);
     }
+    Browser.mainLoop.scheduler();
   },
 
   emscripten_cancel_main_loop: function(func) {
-    _emscripten_set_main_loop.cancel = true;
+    Browser.mainLoop.scheduler = null;
+    Browser.mainLoop.paused = true;
+  },
+
+  emscripten_pause_main_loop: function(func) {
+    Browser.mainLoop.paused = true;
+  },
+
+  emscripten_resume_main_loop: function(func) {
+    Browser.mainLoop.paused = false;
+    Browser.mainLoop.scheduler();
   },
 
   emscripten_async_call: function(func, millis) {
diff --git a/system/include/emscripten.h b/system/include/emscripten.h
index 4725e68a..fdccfe82 100644
--- a/system/include/emscripten.h
+++ b/system/include/emscripten.h
@@ -24,8 +24,18 @@ extern void emscripten_async_run_script(const char *script, int millis);
  * will call that function at a specified number of frames per
  * second. Setting 0 or a negative value as the fps will use
  * the browser's requestAnimationFrame mechanism.
+ *
+ * Pausing and resuming the main loop is useful if your app
+ * needs to perform some synchronous operation, for example
+ * to load a file from the network. It might be wrong to
+ * run the main loop before that finishes (the original
+ * code assumes that), so you can break the code up into
+ * asynchronous callbacks, but you must pause the main
+ * loop until they complete.
  */
 extern void emscripten_set_main_loop(void (*func)(), int fps);
+extern void emscripten_pause_main_loop();
+extern void emscripten_resume_main_loop();
 extern void emscripten_cancel_main_loop();
 
 /*
diff --git a/tests/emscripten_api_browser.cpp b/tests/emscripten_api_browser.cpp
index a2a19359..20e2dbb5 100644
--- a/tests/emscripten_api_browser.cpp
+++ b/tests/emscripten_api_browser.cpp
@@ -9,11 +9,20 @@ int last = 0;
 
 extern "C" {
 
+bool fived = false;
+void five() {
+  fived = true;
+  emscripten_resume_main_loop();
+}
+
 void mainey() {
   static int counter = 0;
   printf("mainey: %d\n", counter++);
-  if (counter == 10) {
-    int result = 1;
+  if (counter == 20) {
+    emscripten_pause_main_loop();
+    emscripten_async_call(five, 1000);
+  } else if (counter == 22) { // very soon after 20, so without pausing we fail
+    int result = fived;
     REPORT_RESULT();
   }
 }