From 20b54d6c7ed671dd7a6e5b2518d338d67e81a543 Mon Sep 17 00:00:00 2001
From: mobserveur <mobserveur@gmail.com>
Date: Sat, 29 Jun 2024 22:50:42 +0200
Subject: Reworked fps limiter code

This improves the realiability of the fps limiter
---
 indra/newview/llappviewer.cpp | 37 ++++++++++++-------------------------
 1 file changed, 12 insertions(+), 25 deletions(-)

(limited to 'indra')

diff --git a/indra/newview/llappviewer.cpp b/indra/newview/llappviewer.cpp
index 2d65c725b5..0f1b5a789b 100644
--- a/indra/newview/llappviewer.cpp
+++ b/indra/newview/llappviewer.cpp
@@ -393,7 +393,6 @@ static std::string gLaunchFileOnQuit;
 // Used on Win32 for other apps to identify our window (eg, win_setup)
 const char* const VIEWER_WINDOW_CLASSNAME = "Second Life";
 
-U64 fpsLimitSleepUntil = 0; // fps limiter : time until to render the frame again
 
 //----------------------------------------------------------------------------
 
@@ -1373,21 +1372,11 @@ bool LLAppViewer::frame()
 
 bool LLAppViewer::doFrame()
 {
+    static LLCachedControl<U32> fpsLimitMaxFps(gSavedSettings, "MaxFPS", 0);
 
-    // FPS Limit
-
-    U64 fpsLimitNow = LLTrace::BlockTimer::getCPUClockCount64();
-    U64 fpsLimitFrameStartTime = fpsLimitNow;
-    if(fpsLimitSleepUntil > 0)
-    {
-        if(fpsLimitSleepUntil > fpsLimitNow) return 0;
-    }
-    else
-    {
-        fpsLimitSleepUntil = 0;
-    }
-
-
+    U64 fpsLimitSleepFor = 0;
+    U64 fpsLimitFrameStartTime = 0;
+    if(fpsLimitMaxFps > 0) fpsLimitFrameStartTime = LLTrace::BlockTimer::getCPUClockCount64();
 
     LL_RECORD_BLOCK_TIME(FTM_FRAME);
     {
@@ -1559,24 +1548,17 @@ bool LLAppViewer::doFrame()
             }
         }
 
-        // fps limiter
-
-        fpsLimitNow = LLTrace::BlockTimer::getCPUClockCount64();
-        U64 fpsLimitFrameTime = fpsLimitNow - fpsLimitFrameStartTime;
-        static LLCachedControl<U32> fpsLimitMaxFps(gSavedSettings, "MaxFPS", 0);
-
         if(fpsLimitMaxFps > 0)
         {
+            U64 fpsLimitFrameTime = LLTrace::BlockTimer::getCPUClockCount64() - fpsLimitFrameStartTime;
             U64 desired_time_ns = (U32)(1000000.f / fpsLimitMaxFps);
 
-            if(fpsLimitFrameTime < desired_time_ns)
+            if((fpsLimitFrameTime+1000) < desired_time_ns)
             {
-                U64 fpsLimitSleepUntil_for = desired_time_ns - fpsLimitFrameTime;
-                fpsLimitSleepUntil = LLTrace::BlockTimer::getCPUClockCount64() + fpsLimitSleepUntil_for;
+                fpsLimitSleepFor = (desired_time_ns - fpsLimitFrameTime - 1000) * 1.0;
             }
         }
 
-
         {
             LL_PROFILE_ZONE_NAMED_CATEGORY_APP( "df pauseMainloopTimeout" )
         pingMainloopTimeout("Main:Sleep");
@@ -1589,6 +1571,11 @@ bool LLAppViewer::doFrame()
             //LL_RECORD_BLOCK_TIME(SLEEP2);
             LL_PROFILE_ZONE_WARN( "Sleep2" )
 
+            if(fpsLimitSleepFor)
+            {
+                usleep(fpsLimitSleepFor);
+            }
+
             // yield some time to the os based on command line option
             static LLCachedControl<S32> yield_time(gSavedSettings, "YieldTime", -1);
             if(yield_time >= 0)
-- 
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