New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/drape_frontend/message_queue.hpp

@@ -0,0 +1,49 @@
+#pragma once
+
+#include "drape_frontend/message.hpp"
+
+#include "drape/drape_diagnostics.hpp"
+#include "drape/pointers.hpp"
+
+#include <condition_variable>
+#include <deque>
+#include <functional>
+#include <mutex>
+
+namespace df
+{
+class MessageQueue
+{
+public:
+  MessageQueue();
+  ~MessageQueue();
+
+  // If the queue is empty then it returns nullptr or wait for a message.
+  drape_ptr<Message> PopMessage(bool waitForMessage);
+  void PushMessage(drape_ptr<Message> && message, MessagePriority priority);
+  void CancelWait();
+  void ClearQuery();
+
+  using FilterMessageFn = std::function<bool(ref_ptr<Message>)>;
+  void EnableMessageFiltering(FilterMessageFn && filter);
+  void DisableMessageFiltering();
+  void InstantFilter(FilterMessageFn && filter);
+
+#ifdef DEBUG_MESSAGE_QUEUE
+  bool IsEmpty() const;
+  size_t GetSize() const;
+#endif
+
+private:
+  void FilterMessagesImpl();
+  void CancelWaitImpl();
+
+  mutable std::mutex m_mutex;
+  std::condition_variable m_condition;
+  bool m_isWaiting;
+  using TMessageNode = std::pair<drape_ptr<Message>, MessagePriority>;
+  std::deque<TMessageNode> m_messages;
+  std::deque<drape_ptr<Message>> m_lowPriorityMessages;
+  FilterMessageFn m_filter;
+};
+}  // namespace df