CONS_Printf: don't blit the screen during startup if this isn't the main thread

src/console.c

@@ -1452,6 +1452,13 @@ void CONS_Printf(const char *fmt, ...)
 
 	Unlock_state();
 
+#ifdef HAVE_THREADS
+	if (! I_on_main_thread())
+	{
+		return;
+	}
+#endif
+
 	// if not in display loop, force screen update
 	if (startup)
 	{

src/i_threads.h

@@ -27,6 +27,8 @@ void      I_spawn_thread (const char *name, I_thread_fn, void *userdata);
 /* check in your thread whether to return early */
 int       I_thread_is_stopped (void);
 
+int       I_on_main_thread  (void);
+
 void      I_lock_mutex      (I_mutex *);
 void      I_unlock_mutex    (I_mutex);
 

src/sdl/i_threads.c

@@ -47,6 +47,8 @@ static I_mutex        i_cond_pool_mutex;
 
 static SDL_atomic_t   i_threads_running = {1};
 
+static SDL_threadID   i_main_thread_id;
+
 static Link
 Insert_link (
 		Link * head,
@@ -197,6 +199,12 @@ I_thread_is_stopped (void)
 	return ( ! SDL_AtomicGet(&i_threads_running) );
 }
 
+int
+I_on_main_thread (void)
+{
+	return ( SDL_ThreadID() == i_main_thread_id );
+}
+
 void
 I_start_threads (void)
 {
@@ -211,6 +219,8 @@ I_start_threads (void)
 	)){
 		abort();
 	}
+
+	i_main_thread_id = SDL_ThreadID();
 }
 
 void