git-svn-id: svn://svn.ijw.co.nz/svn/OpenRa@1138 993157c7-ee19-0410-b2c4-bb4e9862e678

OpenRa.Game/Clock.cs

@@ -0,0 +1,109 @@
+namespace OpenRa.Game
+{
+	/// <summary>
+	/// Provides access to the current time, frame time, and frame rate.
+	/// </summary>
+	public static class Clock
+	{
+		/// <summary>
+		/// Performs one-time initialization for the clock service
+		/// </summary>
+		static Clock()
+		{
+			startTime = System.Environment.TickCount;
+			StartFrame();
+		}
+
+		public static void Reset()
+		{
+			frameCount = 0;
+			lastFrameCount = 0;
+			lastFrameRate = 0;
+			startTime = System.Environment.TickCount;
+			StartFrame();
+		}
+
+		#region StartFrame
+
+		/// <summary>
+		/// Indicates to the clock that a new frame has begun. This should be called exactly once per frame.
+		/// </summary>
+		public static void StartFrame() 
+		{
+			int ticks = System.Environment.TickCount - startTime;
+			frameStartTime = ticks / 1000.0;
+
+			frameCount++;
+
+			if( Time > nextFrameRateUpdateTime )
+			{
+				// set next update time
+				nextFrameRateUpdateTime += (1.0 / FramerateUpdateFrequency);
+				// average between last and current frame, to make spikes less severe
+				const int OldFramerateWeight = 10;
+				const int NewFramerateWeight = 1;
+				int newFrameRate = (frameCount - lastFrameCount) * FramerateUpdateFrequency;
+				lastFrameRate = (lastFrameRate * OldFramerateWeight + NewFramerateWeight * newFrameRate) / (OldFramerateWeight + NewFramerateWeight );
+				lastFrameCount = frameCount;
+			}
+		}
+
+		#endregion
+
+		#region Private Implementation Details
+
+		// number of framerate updates per second
+		private const int FramerateUpdateFrequency = 10;
+		
+		// the time at which the application started
+		private static int startTime;
+		// the time at which this frame began
+		private static double frameStartTime;
+		// total number of frames rendered
+		private static int frameCount = 0;
+		// next time to update fps count
+		private static double nextFrameRateUpdateTime = 0;
+		// frame count at most recent fps calculation
+		private static int lastFrameCount = 0;
+		// most recently calculated fps
+		private static int lastFrameRate = 0;
+
+		#endregion
+
+		#region Properties
+
+		/// <summary>
+		/// The time the current frame started
+		/// </summary>
+		public static double Time 
+		{
+			get { return frameStartTime; }
+		}
+
+		/// <summary>
+		/// The number of frames rendered since the engine started
+		/// </summary>
+		public static int FrameCount
+		{
+			get { return frameCount; }
+		}
+
+		/// <summary>
+		/// The most recent frame-rate
+		/// </summary>
+		public static int FrameRate
+		{
+			get { return lastFrameRate; }
+		}
+
+		/// <summary>
+		/// The frame time corresponding to the most recent frame-rate
+		/// </summary>
+		public static double FrameTime
+		{
+			get { return 1.0 / lastFrameRate; }
+		}
+
+		#endregion
+	}
+}