feat(timer): improve high-FPS timing with high-resolution Windows clock

3 files changed, 21 insertions, 4 deletions

diff --git a/Minecraft.Client/Timer.cpp b/Minecraft.Client/Timer.cpp
index b451c034..15a2c2f1 100644
--- a/Minecraft.Client/Timer.cpp
+++ b/Minecraft.Client/Timer.cpp
@@ -22,8 +22,9 @@ void Timer::advanceTime()
 {
     __int64 nowMs = System::currentTimeMillis();
     __int64 passedMs = nowMs - lastMs;
-    __int64 msSysTime = System::nanoTime() / 1000000;
-    double now = msSysTime / 1000.0;
+    
+    // 4J - Use high-resolution timer for 'now' in seconds
+    double now = System::nanoTime() / 1000000000.0;
 
 
     if (passedMs > 1000)
@@ -39,6 +40,7 @@ void Timer::advanceTime()
         accumMs += passedMs;
         if (accumMs > 1000)
 		{
+            __int64 msSysTime = (__int64)(now * 1000.0);
             __int64 passedMsSysTime = msSysTime - lastMsSysTime;
 
             double adjustTimeT = accumMs / (double) passedMsSysTime;
@@ -49,7 +51,7 @@ void Timer::advanceTime()
         }
         if (accumMs < 0)
 		{
-            lastMsSysTime = msSysTime;
+            lastMsSysTime = (__int64)(now * 1000.0);
         }
     }
     lastMs = nowMs;
@@ -68,7 +70,6 @@ void Timer::advanceTime()
     if (ticks > MAX_TICKS_PER_UPDATE) ticks = MAX_TICKS_PER_UPDATE;
 
     a = passedTime;
-
 }
 
 void Timer::advanceTimeQuickly()
diff --git a/Minecraft.World/system.cpp b/Minecraft.World/system.cpp
index 72727e20..cce04bdc 100644
--- a/Minecraft.World/system.cpp
+++ b/Minecraft.World/system.cpp
@@ -52,7 +52,22 @@ void System::arraycopy(arrayWithLength<int> src, unsigned int srcPos, arrayWithL
 //The current value of the system timer, in nanoseconds.
 __int64 System::nanoTime()
 {
+#if defined _WINDOWS64 || defined _XBOX || defined _WIN32
+	static LARGE_INTEGER s_frequency = { 0 };
+	if (s_frequency.QuadPart == 0)
+	{
+		QueryPerformanceFrequency(&s_frequency);
+	}
+
+	LARGE_INTEGER counter;
+	QueryPerformanceCounter(&counter);
+
+	// Using double to avoid 64-bit overflow during multiplication for long uptime
+	// Precision is sufficient for ~100 days of uptime.
+	return (__int64)((double)counter.QuadPart * 1000000000.0 / (double)s_frequency.QuadPart);
+#else
 	return GetTickCount() * 1000000LL;
+#endif
 }
 
 //Returns the current time in milliseconds. Note that while the unit of time of the return value is a millisecond,
diff --git a/README.md b/README.md
index be3e745b..f32b11fc 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,7 @@ This project contains the source code of Minecraft Legacy Console Edition v1.3.0
 - Added support for keyboard and mouse input
 - Added fullscreen mode support (toggle using F11)
 - Disabled V-Sync for better performance
+- Added a high-resolution timer path on Windows for smoother high-FPS gameplay timing
 - Device's screen resolution will be used as the game resolution instead of using a fixed resolution (1920x1080)
 
 ## Controls (Keyboard & Mouse)