Compensate for excess sleep time in increasetickskk/increaseticks-sleep-adjust-1

1 files changed, 19 insertions, 2 deletions

diff --git a/src/dosbox.cpp b/src/dosbox.cpp
index 07f998985..723bfa91e 100644
--- a/src/dosbox.cpp
+++ b/src/dosbox.cpp
@@ -166,7 +166,11 @@ static Bitu Normal_Loop() {
 	}
 }
 
-void increaseticks() { //Make it return ticksRemain and set it in the function above to remove the global variable.
+static auto extraSleptUs = std::chrono::microseconds(0);
+
+void increaseticks()
+{ // Make it return ticksRemain and set it in the function above to remove the
+  // global variable.
 	ZoneScoped
 	if (GCC_UNLIKELY(ticksLocked)) { // For Fast Forward Mode
 		ticksRemain=5;
@@ -184,12 +188,25 @@ void increaseticks() { //Make it return ticksRemain and set it in the function a
 		ticksAdded = 0;
 
 		constexpr auto duration = std::chrono::milliseconds(1);
+
+		const auto sleepStart = std::chrono::steady_clock::now();
 		std::this_thread::sleep_for(duration);
+		const auto sleepEnd = std::chrono::steady_clock::now();
+		const auto sleptUs = std::chrono::duration_cast<std::chrono::microseconds>(
+		        sleepEnd - sleepStart);
+
+		extraSleptUs += sleptUs % duration;
 
-		const auto timeslept = GetTicksSince(ticksNew);
+		auto timeslept = GetTicksSince(ticksNew);
+
+		if (extraSleptUs >= duration) {
+			timeslept++;
+			extraSleptUs -= duration;
+		}
 
 		// Update ticksDone with the time spent sleeping
 		ticksDone -= timeslept;
+
 		if (ticksDone < 0)
 			ticksDone = 0;
 		return; //0