From f8cb4807797949532fb708839e897f408bc79c07 Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <stenzek@gmail.com>
Date: Sun, 4 Dec 2022 15:40:46 +1000
Subject: [PATCH] Timer: Improve SleepUntil()

---
 src/common/timer.cpp      | 14 +++++++-------
 src/core/host_display.cpp |  7 ++++++-
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/common/timer.cpp b/src/common/timer.cpp
index 41ffbde81..73805b787 100644
--- a/src/common/timer.cpp
+++ b/src/common/timer.cpp
@@ -1,4 +1,5 @@
 #include "timer.h"
+#include "types.h"
 #include <cstdio>
 #include <cstdlib>
 
@@ -109,20 +110,19 @@ void Timer::SleepUntil(Value value, bool exact)
   }
   else
   {
-    const std::int64_t diff = static_cast<std::int64_t>(value - GetCurrentValue());
+    const s64 diff = static_cast<s64>(value - GetCurrentValue());
     if (diff <= 0)
       return;
 
     HANDLE timer = GetSleepTimer();
     if (timer)
     {
-      FILETIME ft;
-      GetSystemTimeAsFileTime(&ft);
+      const u64 one_hundred_nanos_diff = static_cast<u64>(ConvertValueToNanoseconds(diff) / 100.0);
+      if (one_hundred_nanos_diff == 0)
+        return;
 
       LARGE_INTEGER fti;
-      fti.LowPart = ft.dwLowDateTime;
-      fti.HighPart = ft.dwHighDateTime;
-      fti.QuadPart += diff;
+      fti.QuadPart = -static_cast<s64>(one_hundred_nanos_diff);
 
       if (SetWaitableTimer(timer, &fti, 0, nullptr, nullptr, FALSE))
       {
@@ -132,7 +132,7 @@ void Timer::SleepUntil(Value value, bool exact)
     }
 
     // falling back to sleep... bad.
-    Sleep(static_cast<DWORD>(static_cast<std::uint64_t>(diff) / 1000000));
+    Sleep(static_cast<DWORD>(static_cast<u64>(diff) / 1000000));
   }
 }
 
diff --git a/src/core/host_display.cpp b/src/core/host_display.cpp
index 36e05526a..79e2d6620 100644
--- a/src/core/host_display.cpp
+++ b/src/core/host_display.cpp
@@ -124,12 +124,17 @@ void HostDisplay::ThrottlePresentation()
   const u64 sleep_period = Common::Timer::ConvertNanosecondsToValue(1e+9f / static_cast<double>(throttle_rate));
   const u64 current_ts = Common::Timer::GetCurrentValue();
 
-  if (current_ts >= m_last_frame_displayed_time)
+  // Allow it to fall behind/run ahead up to 2*period. Sleep isn't that precise, plus we need to
+  // allow time for the actual rendering.
+  const u64 max_variance = sleep_period * 2;
+  if (static_cast<u64>(std::abs(static_cast<s64>(current_ts - m_last_frame_displayed_time))) > max_variance)
     m_last_frame_displayed_time = current_ts + sleep_period;
   else
     m_last_frame_displayed_time += sleep_period;
 
+  Common::Timer tt;
   Common::Timer::SleepUntil(m_last_frame_displayed_time, false);
+  Log_WarningPrintf("sleep time %.2f ms", tt.GetTimeMilliseconds());
 }
 
 bool HostDisplay::GetHostRefreshRate(float* refresh_rate)