From 79f736b75fa292c5130ef0a4484b8002ce452465 Mon Sep 17 00:00:00 2001
From: Sally Coolatta <tehrealsalt@gmail.com>
Date: Thu, 19 May 2022 16:37:33 -0400
Subject: [PATCH] Use double instead of precise_t for FPS counter

Makes the displayed FPS more accurate to what it's actually displaying.

Also removed HUDTRANS from it -- stop it fading out during level transitions, it's annoying when I actually want to see the FPS during those bits.
---
 src/screen.c | 58 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 36 insertions(+), 22 deletions(-)

diff --git a/src/screen.c b/src/screen.c
index 9cac11263..ef1e1d323 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -454,55 +454,69 @@ boolean SCR_IsAspectCorrect(INT32 width, INT32 height)
 
 double averageFPS = 0.0f;
 
-#define FPS_SAMPLE_RATE (50000) // How often to update FPS samples, in microseconds
-#define NUM_FPS_SAMPLES 16 // Number of samples to store
+#define USE_FPS_SAMPLES
+
+#ifdef USE_FPS_SAMPLES
+#define FPS_SAMPLE_RATE (0.05) // How often to update FPS samples, in seconds
+#define NUM_FPS_SAMPLES (16) // Number of samples to store
 
 static double fps_samples[NUM_FPS_SAMPLES];
+static double updateElapsed = 0.0;
+#endif
+
+static boolean fps_init = false;
+static precise_t fps_enter = 0;
 
 void SCR_CalculateFPS(void)
 {
-	static boolean init = false;
+	precise_t fps_finish = 0;
 
-	static precise_t startTime = 0;
-	precise_t endTime = 0;
+	double frameElapsed = 0.0;
 
-	static precise_t updateTime = 0;
-	int updateElapsed = 0;
-	int i;
-
-	endTime = I_GetPreciseTime();
-
-	if (init == false)
+	if (fps_init == false)
 	{
-		startTime = updateTime = endTime;
-		init = true;
-		return;
+		fps_enter = I_GetPreciseTime();
+		fps_init = true;
 	}
 
-	updateElapsed = (endTime - updateTime) / (I_GetPrecisePrecision() / 1000000);
+	fps_finish = I_GetPreciseTime();
+	frameElapsed = (double)((INT64)(fps_finish - fps_enter)) / I_GetPrecisePrecision();
+	fps_enter = fps_finish;
+
+#ifdef USE_FPS_SAMPLES
+	updateElapsed += frameElapsed;
 
 	if (updateElapsed >= FPS_SAMPLE_RATE)
 	{
 		static int sampleIndex = 0;
-		int frameElapsed = (endTime - startTime) / (I_GetPrecisePrecision() / 1000000);
+		int i;
 
-		fps_samples[sampleIndex] = frameElapsed / 1000.0f;
+		fps_samples[sampleIndex] = frameElapsed;
 
 		sampleIndex++;
 		if (sampleIndex >= NUM_FPS_SAMPLES)
 			sampleIndex = 0;
 
-		averageFPS = 0.0f;
+		averageFPS = 0.0;
 		for (i = 0; i < NUM_FPS_SAMPLES; i++)
 		{
 			averageFPS += fps_samples[i];
 		}
-		averageFPS = 1000.0f / (averageFPS / NUM_FPS_SAMPLES);
 
-		updateTime = endTime;
+		if (averageFPS > 0.0)
+		{
+			averageFPS = 1.0 / (averageFPS / NUM_FPS_SAMPLES);
+		}
 	}
 
-	startTime = endTime;
+	while (updateElapsed >= FPS_SAMPLE_RATE)
+	{
+		updateElapsed -= FPS_SAMPLE_RATE;
+	}
+#else
+	// Direct, unsampled counter.
+	averageFPS = 1.0 / frameElapsed;
+#endif
 }
 
 void SCR_DisplayTicRate(void)