PIStateMachine::postEvent() now thread-safe and can be recursive

libs/main/state_machine/pistatemachine.h

@@ -45,11 +45,27 @@ public:
 	template<typename... Args>
 	bool postEvent(int event_id, Args... args) {
 		if (!is_running) return false;
+		if (in_post.exchange(true)) {
+			PIMutexLocker ml(nested_mutex);
+			nested_posts.enqueue([this, event_id, args...] { postEvent(event_id, args...); });
+			// piCout << "queue nested post";
+			return false;
+		}
 		need_finish = false;
 		PIScopeExitCall exit_call([this] {
+			in_post = false;
 			if (need_finish) {
 				is_running = false;
 				if (on_finish) on_finish();
+			} else {
+				nested_mutex.lock();
+				while (nested_posts.isNotEmpty()) {
+					auto np = nested_posts.dequeue();
+					nested_mutex.unlock();
+					np();
+					nested_mutex.lock();
+				}
+				nested_mutex.unlock();
 			}
 		});
 		PIVector<PIStateBase *> active_states;
@@ -71,6 +87,9 @@ private:
 	void onFinish() override;
 
 	bool is_running = false, need_finish = false;
+	PIQueue<std::function<void()>> nested_posts;
+	PIMutex nested_mutex;
+	std::atomic_bool in_post = {false};
 	std::function<void()> on_finish;
 };