Revert midi::InputQueue to use a priority queue again. Add sequence number to queue to preserve insertion order.

src/midi.cpp

@@ -1,7 +1,8 @@
 #include <map>
 #include <utility>
-#include <deque>
+#include <queue>
 #include <mutex>
+#include <tuple>
 
 #include <midi.hpp>
 #include <string.hpp>
@@ -286,11 +287,26 @@ std::vector<int> Input::getChannels() {
 // InputQueue
 ////////////////////
 
+struct SeqMessage {
+	Message message;
+	uint64_t seq;
+
+	/** Returns whether `this` is LATER in time than `other`.
+	If frame is same, compares `seq`.
+	*/
+	bool operator<(const SeqMessage& other) const {
+		return std::make_tuple(message.getFrame(), seq) > std::make_tuple(other.message.getFrame(), other.seq);
+	}
+};
+
 static const size_t InputQueue_maxSize = 8192;
 
 struct InputQueue::Internal {
-	std::deque<Message> queue;
+	std::priority_queue<SeqMessage> queue;
 	std::mutex mutex;
+	/** Index to preserve ordering for priority_queue since it's unstable.
+	*/
+	uint64_t nextSeq = 0;
 };
 
 InputQueue::InputQueue() {
@@ -306,16 +322,9 @@ void InputQueue::onMessage(const Message& message) {
 	// Reject MIDI message if queue is full
 	if (internal->queue.size() >= InputQueue_maxSize)
 		return;
-	// Message timestamp must be monotonically increasing, otherwise clear the queue.
-	if (!internal->queue.empty()) {
-		const Message& lastMessage = internal->queue.back();
-		if (message.getFrame() < lastMessage.getFrame()) {
-			WARN("MIDI message at frame %lld added to InputQueue after later message at frame %lld", (long long) message.getFrame(), (long long) lastMessage.getFrame());
-			internal->queue.clear();
-		}
-	}
 	// Push to queue
-	internal->queue.push_back(message);
+	internal->queue.push({message, internal->nextSeq});
+	internal->nextSeq++;
 }
 
 bool InputQueue::tryPop(Message* messageOut, int64_t maxFrame) {
@@ -328,10 +337,10 @@ bool InputQueue::tryPop(Message* messageOut, int64_t maxFrame) {
 	if (internal->queue.empty())
 		return false;
 
-	const Message& message = internal->queue.front();
-	if (message.getFrame() <= maxFrame) {
-		*messageOut = message;
-		internal->queue.pop_front();
+	const SeqMessage& s = internal->queue.top();
+	if (s.message.getFrame() <= maxFrame) {
+		*messageOut = s.message;
+		internal->queue.pop();
 		return true;
 	}