From 37387e151f298b1b8e7948d8410a39103f9db782 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Fri, 23 Jun 2017 16:43:10 -0700
Subject: [PATCH] Batch mouse movement events to reduce input lag with high
 polling rate mice

---
 input.cpp     | 12 +++++++++++-
 main.cpp      |  7 ++++---
 moonlight.hpp |  8 ++++++--
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/input.cpp b/input.cpp
index 2fc0b91..bab7617 100644
--- a/input.cpp
+++ b/input.cpp
@@ -51,6 +51,13 @@ static char GetModifierFlags(const pp::InputEvent& event) {
     return flags;
 }
 
+void MoonlightInstance::ReportMouseMovement() {
+    if (m_MouseDeltaX != 0 || m_MouseDeltaY != 0) {
+        LiSendMouseMoveEvent(m_MouseDeltaX, m_MouseDeltaY);
+        m_MouseDeltaX = m_MouseDeltaY = 0;
+    }
+}
+
 bool MoonlightInstance::HandleInputEvent(const pp::InputEvent& event) {
     switch (event.GetType()) {
         case PP_INPUTEVENT_TYPE_MOUSEDOWN: {
@@ -77,7 +84,10 @@ bool MoonlightInstance::HandleInputEvent(const pp::InputEvent& event) {
             pp::MouseInputEvent mouseEvent(event);
             pp::Point posDelta = mouseEvent.GetMovement();
             
-            LiSendMouseMoveEvent(posDelta.x(), posDelta.y());
+            // Wait to report mouse movement until the next input polling window
+            // to allow batching to occur which reduces overall input lag.
+            m_MouseDeltaX += posDelta.x();
+            m_MouseDeltaY += posDelta.y();
             return true;
         }
         
diff --git a/main.cpp b/main.cpp
index 8132e95..c92a6c3 100644
--- a/main.cpp
+++ b/main.cpp
@@ -85,18 +85,19 @@ void* MoonlightInstance::StopThreadFunc(void* context) {
 
     // We also need to stop this thread after the connection thread, because it depends
     // on being initialized there.
-    pthread_join(g_Instance->m_GamepadThread, NULL);
+    pthread_join(g_Instance->m_InputThread, NULL);
 
     // Stop the connection
     LiStopConnection();
     return NULL;
 }
 
-void* MoonlightInstance::GamepadThreadFunc(void* context) {
+void* MoonlightInstance::InputThreadFunc(void* context) {
     MoonlightInstance* me = (MoonlightInstance*)context;
 
     while (me->m_Running) {
         me->PollGamepads();
+        me->ReportMouseMovement();
         
         // Poll every 10 ms
         usleep(10 * 1000);
@@ -135,7 +136,7 @@ void* MoonlightInstance::ConnectionThreadFunc(void* context) {
     // Set running state before starting connection-specific threads
     me->m_Running = true;
     
-    pthread_create(&me->m_GamepadThread, NULL, MoonlightInstance::GamepadThreadFunc, me);
+    pthread_create(&me->m_InputThread, NULL, MoonlightInstance::InputThreadFunc, me);
     
     return NULL;
 }
diff --git a/moonlight.hpp b/moonlight.hpp
index ac85f36..95ce03c 100644
--- a/moonlight.hpp
+++ b/moonlight.hpp
@@ -59,6 +59,8 @@ class MoonlightInstance : public pp::Instance, public pp::MouseLock {
             m_MouseLocked(false),
             m_WaitingForAllModifiersUp(false),
             m_AccumulatedTicks(0),
+            m_MouseDeltaX(0),
+            m_MouseDeltaY(0),
             openHttpThread(this) {
             // This function MUST be used otherwise sockets don't work (nacl_io_init() doesn't work!)            
             nacl_io_init_ppapi(pp_instance(), pp::Module::Get()->get_browser_interface());
@@ -85,6 +87,7 @@ class MoonlightInstance : public pp::Instance, public pp::MouseLock {
         void PairCallback(int32_t /*result*/, int32_t callbackId, pp::VarArray args);
     
         bool HandleInputEvent(const pp::InputEvent& event);
+        void ReportMouseMovement();
         
         void PollGamepads();
         
@@ -105,7 +108,7 @@ class MoonlightInstance : public pp::Instance, public pp::MouseLock {
         static void ProfilerPrintWarning(const char* message);
 
         static void* ConnectionThreadFunc(void* context);
-        static void* GamepadThreadFunc(void* context);
+        static void* InputThreadFunc(void* context);
         static void* StopThreadFunc(void* context);
         
         static void ClStageStarting(int stage);
@@ -151,7 +154,7 @@ class MoonlightInstance : public pp::Instance, public pp::MouseLock {
         bool m_Running;
         
         pthread_t m_ConnectionThread;
-        pthread_t m_GamepadThread;
+        pthread_t m_InputThread;
     
         pp::Graphics3D m_Graphics3D;
         pp::VideoDecoder* m_VideoDecoder;
@@ -173,6 +176,7 @@ class MoonlightInstance : public pp::Instance, public pp::MouseLock {
         bool m_MouseLocked;
         bool m_WaitingForAllModifiersUp;
         float m_AccumulatedTicks;
+        int32_t m_MouseDeltaX, m_MouseDeltaY;
     
         pp::SimpleThread openHttpThread;
 };