[client/idd] input: reduce network latency

Route input through a dedicated high-priority stream, send pointer
motion as cumulative datagrams, and recover suspected loss reliably.

Reduce downstream input queuing with age-aware coalescing and input
thread scheduling.

client/transports/Network/audio.c

@@ -601,7 +601,7 @@ static LG_TransportStatus networkAudioSendDatagramNL(NetworkAudio * audio,
 {
   return networkConnectionSendDatagram(audio->connection,
       LG_NET_SERVICE_AUDIO, messageType, audio->serviceVersion, 0,
-      audio->subscriptionEpoch, requestID, payload, payloadLength, false);
+      audio->subscriptionEpoch, requestID, payload, payloadLength, 0, false);
 }
 
 static bool networkAudioSendSubscribeNL(NetworkAudio * audio)

client/transports/Network/connection.h

@@ -51,6 +51,8 @@ typedef void (*NetworkConnectionStateFn)(void * opaque, bool connected,
     LG_TransportStatus reason);
 typedef void (*NetworkSendReadyFn)(void * opaque, LGNetService service,
     NetworkPacketDelivery delivery);
+typedef void (*NetworkDatagramLostFn)(void * opaque, LGNetService service,
+    uint64_t componentEpoch, uint64_t applicationSequence);
 
 typedef struct NetworkConnectionParams
 {
@@ -63,6 +65,7 @@ typedef struct NetworkConnectionParams
   NetworkPacketFn            packet;
   NetworkConnectionStateFn   state;
   NetworkSendReadyFn         sendReady;
+  NetworkDatagramLostFn      datagramLost;
   const LGNetCapability    * capabilities;
   uint32_t                   capabilityCount;
   void                     * opaque;
@@ -92,7 +95,8 @@ LG_TransportStatus networkConnectionSendDatagram(
     NetworkConnection * connection, LGNetService service,
     uint16_t messageType, uint16_t serviceVersion,
     LGNetEnvelopeFlags flags, uint64_t componentEpoch, uint64_t requestID,
-    const void * payload, uint32_t payloadLength, bool discardIfBlocked);
+    const void * payload, uint32_t payloadLength,
+    uint64_t applicationSequence, bool discardIfBlocked);
 LG_TransportStatus networkConnectionSendBulk(NetworkConnection * connection,
     LGNetService service, uint16_t messageType, uint16_t serviceVersion,
     LGNetEnvelopeFlags flags, uint64_t componentEpoch, uint64_t requestID,

client/transports/Network/input.h

@@ -37,5 +37,9 @@ void networkInputDestroy(NetworkInput ** input);
 const LG_InputOps * networkInputGetOps(void);
 
 void networkInputConnectionState(NetworkInput * input, bool connected);
+void networkInputSendReady(NetworkInput * input,
+    NetworkPacketDelivery delivery);
+void networkInputDatagramLost(NetworkInput * input,
+    uint64_t claimEpoch, uint64_t pointerSequence);
 bool networkInputPacket(NetworkInput * input,
     const LGNetPacketView * packet, bool datagram);

client/transports/Network/network.c

@@ -58,6 +58,7 @@
 #define NETWORK_FILE_MAX_PAYLOAD      \
   (LG_NET_FILE_CHUNK_HEADER_WIRE_SIZE + NETWORK_TRANSFER_CHUNK)
 #define NETWORK_VIDEO_MAX_PAYLOAD     LG_NET_MAX_PAYLOAD_LENGTH
+#define NETWORK_INPUT_MAX_PAYLOAD     LG_NET_INPUT_ABSOLUTE_WIRE_SIZE
 
 static const LGNetCapability NETWORK_CAPABILITIES[] =
 {
@@ -91,9 +92,9 @@ static const LGNetCapability NETWORK_CAPABILITIES[] =
     .flags                    = LG_NET_CAPABILITY_RELIABLE |
       LG_NET_CAPABILITY_DATAGRAM,
     .features                 = 0,
-    .maxPayloadLength         = NETWORK_MAX_PAYLOAD,
-    .maxDatagramPayload       = NETWORK_MAX_DATAGRAM,
-    .maxBidirectionalStreams  = 0,
+    .maxPayloadLength         = NETWORK_INPUT_MAX_PAYLOAD,
+    .maxDatagramPayload       = NETWORK_INPUT_MAX_PAYLOAD,
+    .maxBidirectionalStreams  = 1,
     .maxUnidirectionalStreams = 0,
   },
   {
@@ -473,6 +474,8 @@ static void networkSendReady(void * opaque, LGNetService service,
   LG_Transport * this     = opaque;
   const bool     datagram =
     delivery == NETWORK_PACKET_DELIVERY_DATAGRAM;
+  if (service == LG_NET_SERVICE_INPUT)
+    networkInputSendReady(this->input, delivery);
   if (service == LG_NET_SERVICE_AUDIO &&
       delivery != NETWORK_PACKET_DELIVERY_BULK)
     networkAudioSendReady(this->audio, datagram);
@@ -484,6 +487,15 @@ static void networkSendReady(void * opaque, LGNetService service,
     networkVideoSendReady(this->video, datagram);
 }
 
+static void networkDatagramLost(void * opaque, LGNetService service,
+    uint64_t componentEpoch, uint64_t applicationSequence)
+{
+  LG_Transport * this = opaque;
+  if (service == LG_NET_SERVICE_INPUT)
+    networkInputDatagramLost(
+        this->input, componentEpoch, applicationSequence);
+}
+
 static bool networkCreate(LG_Transport ** result)
 {
   if (!result)
@@ -552,6 +564,7 @@ static bool networkCreate(LG_Transport ** result)
     .packet          = networkPacket,
     .state           = networkConnectionState,
     .sendReady       = networkSendReady,
+    .datagramLost    = networkDatagramLost,
     .capabilities    = NETWORK_CAPABILITIES,
     .capabilityCount = sizeof(NETWORK_CAPABILITIES) /
       sizeof(NETWORK_CAPABILITIES[0]),

client/transports/Network/video.c

@@ -592,7 +592,7 @@ static LG_TransportStatus networkVideoSendDatagramNL(NetworkVideo * video,
 {
   return networkConnectionSendDatagram(video->connection,
       LG_NET_SERVICE_VIDEO, messageType, video->serviceVersion, 0,
-      componentEpoch, 0, payload, payloadLength, true);
+      componentEpoch, 0, payload, payloadLength, 0, true);
 }
 
 static void networkVideoSendSubscribeNL(NetworkVideo * video, uint64_t now)