Fix percision lost when calculating the frame time. Started after ~4 minutes due to float percision limits, would be visible after ~18-36 hours when it would be off by 4-8ms.

Author: Jarcho

src/d2dx/RenderContext.cpp

@@ -468,8 +468,8 @@ void RenderContext::Present()
 		break;
 	}
 
-	double curTime = TimeEndMs(_timeStart);
-	_frameTimeMs = curTime - _prevTime;
+	auto curTime = TimeEnd(_timeStart);
+	_frameTimeMs = TimeToMs(curTime - _prevTime);
 	_prevTime = curTime;
 
 	if (_deviceContext1)

src/d2dx/RenderContext.h

@@ -211,7 +211,7 @@ namespace d2dx
 		int64_t _timeStart;
 		bool _hasAdjustedWindowPlacement = false;
 
-		double _prevTime;
+		int64_t _prevTime;
 		double _frameTimeMs;
 	};
 }

src/d2dx/Utils.cpp

@@ -51,13 +51,17 @@ int64_t d2dx::TimeStart()
     return (int64_t)li.QuadPart;
 }
 
-float d2dx::TimeEndMs(int64_t sinceThisTime)
+int64_t d2dx::TimeEnd(int64_t sinceThisTime)
 {
-    warmup();
     LARGE_INTEGER li;
     QueryPerformanceCounter(&li);
+    return li.QuadPart - sinceThisTime;
+}
+
+double d2dx::TimeToMs(int64_t time)
+{
     assert(_freq);
-    return (float)(double(li.QuadPart - sinceThisTime) / _freq);
+    return static_cast<double>(time) / _freq;
 }
 
 #define STATUS_SUCCESS (0x00000000)

src/d2dx/Utils.h

@@ -29,7 +29,8 @@ namespace d2dx
 	}
 
 	int64_t TimeStart();
-	float TimeEndMs(int64_t start);
+	int64_t TimeEnd(int64_t start);
+	double TimeToMs(int64_t time);
 
 
 #ifdef NDEBUG