Update main loop to fix reentrancy runtime errors

watch-library/simulator/main.c

@@ -24,39 +24,83 @@
 
 #include <stdio.h>
 #include "watch.h"
+#include "watch_main_loop.h"
 
 #include <emscripten.h>
 #include <emscripten/html5.h>
 
+#define ANIMATION_FRAME_ID_IS_VALID(id) ((id) >= 0)
+#define ANIMATION_FRAME_ID_INVALID (-1)
+#define ANIMATION_FRAME_ID_SUSPENDED (-2)
+
 static bool sleeping = true;
+static volatile long animation_frame_id = ANIMATION_FRAME_ID_INVALID;
+
+// make compiler happy
+static void main_loop_set_sleeping(bool sleeping);
+static EM_BOOL main_loop(double time, void *userData);
+
+static inline void request_next_frame(void) {
+    if (animation_frame_id == ANIMATION_FRAME_ID_INVALID) {
+        animation_frame_id = emscripten_request_animation_frame(main_loop, NULL);
+    }
+}
 
 static EM_BOOL main_loop(double time, void *userData) {
+    if (main_loop_is_sleeping()) {
+        request_next_frame();
+        return EM_FALSE;
+    }
+
     if (sleeping) {
         sleeping = false;
         app_wake_from_standby();
     }
 
+    animation_frame_id = ANIMATION_FRAME_ID_INVALID;
     bool can_sleep = app_loop();
 
     if (can_sleep) {
         app_prepare_for_standby();
         sleeping = true;
+        animation_frame_id = ANIMATION_FRAME_ID_INVALID;
         return EM_FALSE;
     }
 
-    return EM_TRUE;
+    request_next_frame();
+    return EM_FALSE;
 }
 
-// make compiler happy
-void resume_main_loop(void);
-
-EMSCRIPTEN_KEEPALIVE
 void resume_main_loop(void) {
-    if (sleeping) {
-        emscripten_request_animation_frame_loop(main_loop, NULL);
+    if (!ANIMATION_FRAME_ID_IS_VALID(animation_frame_id)) {
+        animation_frame_id = emscripten_request_animation_frame(main_loop, NULL);
     }
 }
 
+void suspend_main_loop(void) {
+    if (ANIMATION_FRAME_ID_IS_VALID(animation_frame_id)) {
+        emscripten_cancel_animation_frame(animation_frame_id);
+    }
+
+    animation_frame_id = ANIMATION_FRAME_ID_SUSPENDED;
+}
+
+void main_loop_sleep(uint32_t ms) {
+    main_loop_set_sleeping(true);
+    emscripten_sleep(ms);
+    main_loop_set_sleeping(false);
+}
+
+bool main_loop_is_sleeping(void) {
+    return EM_ASM_INT({ return Module['suspended']; }) != 0;
+}
+
+static void main_loop_set_sleeping(bool sleeping) {
+    EM_ASM({
+        Module['suspended'] = $0;
+    }, sleeping);
+}
+
 int main(void) {
     printf("Hello, world!\n");