From 1f96c3a2b3c97ea8e2856673f78e0f0f5f330c12 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Sat, 1 Mar 2025 19:13:06 +0100
Subject: [PATCH] Switch to sleep_precise for WaitUntil() which is used for
 frame timing.

This can improve frame pacing slightly, not just on Windows actually.
---
 Common/TimeUtil.cpp  | 14 ++++++++------
 Core/FrameTiming.cpp | 11 ++++++++++-
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/Common/TimeUtil.cpp b/Common/TimeUtil.cpp
index b1a1798136..1f16898d18 100644
--- a/Common/TimeUtil.cpp
+++ b/Common/TimeUtil.cpp
@@ -51,6 +51,7 @@ void TimeInit() {
 	QpcPerSecond = frequency.QuadPart;
 	frequencyMult = 1.0 / static_cast<double>(frequency.QuadPart);
 
+	// The timer will be automatically deleted on process destruction. Don't need to CloseHandle.
 	Timer = CreateWaitableTimerExW(NULL, NULL, CREATE_WAITABLE_TIMER_HIGH_RESOLUTION, TIMER_ALL_ACCESS);
 #if !PPSSPP_PLATFORM(UWP)
 	TIMECAPS caps;
@@ -264,11 +265,13 @@ void sleep_ms(int ms, const char *reason) {
 #endif
 }
 
-// Precise Windows sleep function from: https://github.com/blat-blatnik/Snippets/blob/main/precise_sleep.c
-// Described in: https://blog.bearcats.nl/perfect-sleep-function/
-
 void sleep_precise(double seconds) {
+	if (seconds <= 0.0) {
+		return;
+	}
 #ifdef _WIN32
+	// Precise Windows sleep function from: https://github.com/blat-blatnik/Snippets/blob/main/precise_sleep.c
+	// Described in: https://blog.bearcats.nl/perfect-sleep-function/
 	LARGE_INTEGER qpc;
 	QueryPerformanceCounter(&qpc);
 	INT64 targetQpc = (INT64)(qpc.QuadPart + seconds * QpcPerSecond);
@@ -302,15 +305,14 @@ void sleep_precise(double seconds) {
 		YieldProcessor();
 		QueryPerformanceCounter(&qpc);
 	}
-#else
-#if defined(HAVE_LIBNX)
+	// On other platforms, we just do a conversion with more input precision than in sleep_ms which is restricted to whole milliseconds.
+#elif defined(HAVE_LIBNX)
 	svcSleepThread((int64_t)(seconds * 1000000000.0));
 #elif defined(__EMSCRIPTEN__)
 	emscripten_sleep(seconds * 1000.0);
 #else
 	usleep(seconds * 1000000.0);
 #endif
-#endif
 }
 
 // Return the current time formatted as Minutes:Seconds:Milliseconds
diff --git a/Core/FrameTiming.cpp b/Core/FrameTiming.cpp
index 1d1d84c8ed..b42c70f19a 100644
--- a/Core/FrameTiming.cpp
+++ b/Core/FrameTiming.cpp
@@ -19,6 +19,7 @@
 // * Frame skipping. This gets complicated.
 // * The game not actually asking for flips, like in static loading screens
 
+#include "ppsspp_config.h"
 #include "Common/Profiler/Profiler.h"
 #include "Common/Log.h"
 #include "Common/TimeUtil.h"
@@ -35,7 +36,13 @@
 FrameTiming g_frameTiming;
 
 void WaitUntil(double now, double timestamp, const char *reason) {
-#ifdef _WIN32
+#if 1
+	// Use precise timing.
+	sleep_precise(timestamp - now);
+#else
+
+#if PPSSPP_PLATFORM(WINDOWS)
+	// Old method. TODO: Should we make an option?
 	while (time_now_d() < timestamp) {
 		sleep_ms(1, reason); // Sleep for 1ms on this thread
 	}
@@ -45,6 +52,8 @@ void WaitUntil(double now, double timestamp, const char *reason) {
 		usleep((long)(left * 1000000));
 	}
 #endif
+
+#endif
 }
 
 inline Draw::PresentMode GetBestImmediateMode(Draw::PresentMode supportedModes) {