From 6d14b6fb564cf64521ffb15e91a25dd91f9629a6 Mon Sep 17 00:00:00 2001
From: Thanasis Antoniou
Date: Sun, 1 Sep 2019 22:22:32 +0300
Subject: BLADERUNNER: Framelimiter fixes for delayMillis case

---
 engines/bladerunner/framelimiter.cpp | 39 ++++++++++++++++++++----------------
 engines/bladerunner/framelimiter.h   |  9 +++------
 2 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/engines/bladerunner/framelimiter.cpp b/engines/bladerunner/framelimiter.cpp
index 08cc9fc99b..91277bafb8 100644
--- a/engines/bladerunner/framelimiter.cpp
+++ b/engines/bladerunner/framelimiter.cpp
@@ -70,10 +70,10 @@ Framelimiter::Framelimiter(BladeRunnerEngine *vm, FramelimiterFpsRate framerateM
 
 Framelimiter::~Framelimiter() { }
 
-void Framelimiter::init(bool forceFirstPass) {
+void Framelimiter::init(bool forceScreenUpdate) {
 	reset();
 	_timeOfLastPass = _vm->_time->currentSystem();
-	_forceFirstPass = forceFirstPass;
+	_forceScreenUpdate = forceScreenUpdate;
 }
 
 uint32 Framelimiter::getLastFrameDuration() const {
@@ -92,12 +92,23 @@ bool Framelimiter::shouldExecuteScreenUpdate() {
 	bool shouldUpdateScreen = true;
 	_timeOfCurrentPass = _vm->_time->currentSystem();
 	if (_enabled) {
-		shouldUpdateScreen = ((_timeOfCurrentPass - _timeOfLastPass) >= _speedLimitMs) || _forceFirstPass;
+		if (_useDelayMs) {
+			// _timeOfCurrentPass is used to calculate the duration that the current frame is on screen so far
+			uint32 frameDuration = _timeOfCurrentPass - _startFrameTime;
+			if (frameDuration < _speedLimitMs) {
+				_vm->_system->delayMillis(_speedLimitMs - frameDuration);
+				// cheaper than calling _vm->_time->currentSystem() again
+				_timeOfCurrentPass += (_speedLimitMs - frameDuration);
+			}
+		}
+
+		shouldUpdateScreen = ((_timeOfCurrentPass - _timeOfLastPass) >= _speedLimitMs) || _forceScreenUpdate || _useDelayMs;
 
 		if (shouldUpdateScreen) {
-			if (_forceFirstPass) {
-				_forceFirstPass = false;
+			if (_forceScreenUpdate) {
+				_forceScreenUpdate = false;
 			}
+			_lastFrameDurationMs = _timeOfCurrentPass - _startFrameTime;
 			_startFrameTime = _timeOfCurrentPass;
 		}
 	}
@@ -106,21 +117,15 @@ bool Framelimiter::shouldExecuteScreenUpdate() {
 
 void  Framelimiter::postScreenUpdate() {
 	_timeOfLastPass = _timeOfCurrentPass;
-	if (_enabled) {
-
-		if (_useDelayMs) {
-			uint32 endFrameTime = _vm->_time->currentSystem();
-			uint32 frameDuration = endFrameTime - _startFrameTime;
-
-			if (frameDuration < _speedLimitMs) {
-				_vm->_system->delayMillis(_speedLimitMs - frameDuration);
-			}
-		}
-	}
+//	if (_enabled) {
+//		// for debug purposes, this calculates the time between deciding to draw the frame, and the time after drawing the update to the screen
+//		uint32 endFrameTime = _vm->_time->currentSystem();
+//		uint32 frameDuration = endFrameTime - _startFrameTime;
+//	}
 }
 
 void Framelimiter::reset() {
-	_forceFirstPass      = false;
+	_forceScreenUpdate   = false;
 	_timeOfLastPass      = 0u;
 	_timeOfCurrentPass   = 0u;
 	_startFrameTime      = 0u;
diff --git a/engines/bladerunner/framelimiter.h b/engines/bladerunner/framelimiter.h
index 66ee0f3b38..032457028d 100644
--- a/engines/bladerunner/framelimiter.h
+++ b/engines/bladerunner/framelimiter.h
@@ -43,12 +43,12 @@ class Framelimiter {
 
 public:
 	static const FramelimiterFpsRate kDefaultFpsRate = kFramelimiter60fps;
-	static const bool kDefaultUseDelayMillis = false;
+	static const bool kDefaultUseDelayMillis = true;
 
 private:
 	BladeRunnerEngine *_vm;
 
-	bool   _forceFirstPass;
+	bool   _forceScreenUpdate;
 	uint32 _speedLimitMs;
 
 	// A pass is when a tick or while loop that contains a potential screen update is repeated
@@ -68,12 +68,9 @@ public:
 	Framelimiter(BladeRunnerEngine *vm, FramelimiterFpsRate framerateMode, bool useDelayMs);
 	~Framelimiter();
 
-//	void startFrame();
-//	void delayBeforeSwap();
-
 //	void pause(bool pause);
 
-	void init(bool forceFirstPass = true);
+	void init(bool forceScreenUpdate = true);
 	uint32 getLastFrameDuration() const;
 	uint32 getTimeOfCurrentPass() const;
 	uint32 getTimeOfLastPass() const;
-- 
cgit v1.2.3