Fix simulator crashing on MacOS

Event handling must happen on the main
thread for MacOS.

Not sure if button_queue_wait is the
best place for doing the SDL event
polling, but seems to work ok.

Change-Id: If928282df84bdd74e24a48afd7dbc4c4bfcc49e2

firmware/target/hosted/sdl/button-sdl.c

@@ -307,6 +307,15 @@ static bool event_handler(SDL_Event *event)
     return false;
 }
 
+#ifdef __APPLE__
+void handle_sdl_events(void)
+{
+    SDL_Event event;
+    while(SDL_PollEvent(&event))
+        event_handler(&event);
+}
+#endif
+
 void gui_message_loop(void)
 {
     SDL_Event event;

firmware/target/hosted/sdl/button-sdl.h

@@ -28,6 +28,10 @@
 
 extern int sdl_app_has_input_focus;
 
+#ifdef __APPLE__
+void handle_sdl_events(void);
+#endif
+
 bool button_hold(void);
 #undef button_init_device
 void button_init_device(void);

firmware/target/hosted/sdl/system-sdl.c

@@ -138,6 +138,7 @@ static void sdl_window_setup(void)
     }
 }
 
+#ifndef __APPLE__ /* MacOS requires events to be handled on main thread */
 /*
  * This thread will read the buttons in an interrupt like fashion, and
  * also initializes SDL_INIT_VIDEO and the surfaces
@@ -205,6 +206,7 @@ static int sdl_event_thread(void * param)
 #endif
     return 0;
 }
+#endif
 
 static bool quitting;
 
@@ -270,11 +272,13 @@ void system_init(void)
     sdl_window_setup();
 #endif
 
+#ifndef __APPLE__ /* MacOS requires events to be handled on main thread */
     s = SDL_CreateSemaphore(0); /* 0-count so it blocks */
     evt_thread = SDL_CreateThread(sdl_event_thread, NULL, s);
     SDL_SemWait(s);
     /* cleanup */
     SDL_DestroySemaphore(s);
+#endif
 }