From fb3eb9443e9263aa7f71127b25c73482e6f2088c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Leclercq?=
 <jerome.leclercq@fullcycle.games>
Date: Wed, 7 Feb 2018 15:02:44 +0100
Subject: [PATCH] Core/Clock: Restart now returns the elapsed time in
 milliseconds

---
 ChangeLog.md                           |  1 +
 SDK/src/NDK/Application.cpp            |  3 +--
 examples/FirstScene/main.cpp           |  4 +---
 include/Nazara/Core/Clock.hpp          |  4 ++--
 src/Nazara/Core/Clock.cpp              | 17 ++++++++++++++---
 tests/Engine/Platform/EventHandler.cpp |  3 +--
 6 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index da2a0c98e..1446257a5 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -59,6 +59,7 @@ Nazara Engine:
 - Fix LuaClass not working correctly when Lua stack wasn't empty
 - Add RigidBody2D simulation control (via EnableSimulation and IsSimulationEnabled), which allows to disable physics and collisions at will.
 - ⚠️ LuaInstance no longer load all lua libraries on construction, this is done in the new LoadLibraries method which allows you to excludes some libraries
+- Clock::Restart now returns the elapsed microseconds since construction or last Restart call
 
 Nazara Development Kit:
 - Added ImageWidget (#139)
diff --git a/SDK/src/NDK/Application.cpp b/SDK/src/NDK/Application.cpp
index 5e0f07d00..a4fca055a 100644
--- a/SDK/src/NDK/Application.cpp
+++ b/SDK/src/NDK/Application.cpp
@@ -107,8 +107,7 @@ namespace Ndk
 		if (m_shouldQuit)
 			return false;
 
-		m_updateTime = m_updateClock.GetSeconds();
-		m_updateClock.Restart();
+		m_updateTime = m_updateClock.Restart() / 1'000'000.f;
 
 		for (World& world : m_worlds)
 			world.Update(m_updateTime);
diff --git a/examples/FirstScene/main.cpp b/examples/FirstScene/main.cpp
index 00fbebae1..2aec4861e 100644
--- a/examples/FirstScene/main.cpp
+++ b/examples/FirstScene/main.cpp
@@ -325,9 +325,7 @@ int main()
 	while (application.Run())
 	{
 
-		Nz::UInt64 elapsedUS = updateClock.GetMicroseconds();
-		// On relance l'horloge
-		updateClock.Restart();
+		Nz::UInt64 elapsedUS = updateClock.Restart() / 1'000'000;
 
 		// Mise à jour (Caméra)
 		const Nz::UInt64 updateRate = 1000000 / 60; // 60 fois par seconde
diff --git a/include/Nazara/Core/Clock.hpp b/include/Nazara/Core/Clock.hpp
index 699f1a78c..a6b464db6 100644
--- a/include/Nazara/Core/Clock.hpp
+++ b/include/Nazara/Core/Clock.hpp
@@ -32,7 +32,7 @@ namespace Nz
 			bool IsPaused() const;
 
 			void Pause();
-			void Restart();
+			UInt64 Restart();
 			void Unpause();
 
 			Clock& operator=(const Clock& clock) = default;
@@ -46,7 +46,7 @@ namespace Nz
 			bool m_paused;
 	};
 
-	typedef UInt64 (*ClockFunction)();
+	using ClockFunction = UInt64 (*)();
 
 	extern NAZARA_CORE_API ClockFunction GetElapsedMicroseconds;
 	extern NAZARA_CORE_API ClockFunction GetElapsedMilliseconds;
diff --git a/src/Nazara/Core/Clock.cpp b/src/Nazara/Core/Clock.cpp
index 92183674c..13554a1fa 100644
--- a/src/Nazara/Core/Clock.cpp
+++ b/src/Nazara/Core/Clock.cpp
@@ -67,7 +67,7 @@ namespace Nz
 	*/
 	float Clock::GetSeconds() const
 	{
-		return GetMicroseconds()/1000000.f;
+		return GetMicroseconds()/1'000'000.f;
 	}
 
 	/*!
@@ -132,15 +132,26 @@ namespace Nz
 
 	/*!
 	* \brief Restart the clock
+	* \return Microseconds elapsed
+	*
 	* Restarts the clock, putting it's time counter back to zero (as if the clock got constructed).
+	* It also compute the elapsed microseconds since the last Restart() call without any time loss (a problem that the combination of GetElapsedMicroseconds and Restart have).
 	*/
-	void Clock::Restart()
+	UInt64 Clock::Restart()
 	{
 		NazaraLock(m_mutex);
 
+		Nz::UInt64 now = GetElapsedMicroseconds();
+
+		Nz::UInt64 elapsedTime = m_elapsedTime;
+		if (!m_paused)
+			elapsedTime += (now - m_refTime);
+
 		m_elapsedTime = 0;
-		m_refTime = GetElapsedMicroseconds();
+		m_refTime = now;
 		m_paused = false;
+
+		return elapsedTime;
 	}
 
 	/*!
diff --git a/tests/Engine/Platform/EventHandler.cpp b/tests/Engine/Platform/EventHandler.cpp
index b143b949a..a2f64e9f4 100644
--- a/tests/Engine/Platform/EventHandler.cpp
+++ b/tests/Engine/Platform/EventHandler.cpp
@@ -51,9 +51,8 @@ SCENARIO("EventHandler", "[PLATFORM][EVENTHANDLER][INTERACTIVE][.]")
 		while (app.Run())
 		{
 			window.Display();
-			float elapsedTime = elapsedTimeClock.GetSeconds();
-			elapsedTimeClock.Restart();
 
+			float elapsedTime = elapsedTimeClock.Restart() / 1'000'000;
 			if (!fsm.Update(elapsedTime))
 			{
 				NazaraError("Failed to update state machine.");