From 8bf919f750807060f3ac2c640b8a02300af1733c Mon Sep 17 00:00:00 2001
From: WBoerenkamps <wrj.boerenkamps@student.avans.nl>
Date: Wed, 18 Sep 2024 16:52:54 +0200
Subject: gameloop poc working with variable and constant update

---
 gameloop/include/loopManager.h |  3 +-
 gameloop/include/timer.h       | 29 +++++++++----------
 gameloop/src/loopManager.cpp   | 38 +++++++++++++-----------
 gameloop/src/timer.cpp         | 66 +++++++++++++++++++++++++-----------------
 4 files changed, 75 insertions(+), 61 deletions(-)

diff --git a/gameloop/include/loopManager.h b/gameloop/include/loopManager.h
index 5ed918d..06bcd5f 100644
--- a/gameloop/include/loopManager.h
+++ b/gameloop/include/loopManager.h
@@ -18,9 +18,8 @@ class LoopManager{
 		bool gameRunning = false;
 		WindowManager window;
 		int timeScale = 1;
-		float lag = 0.0;
+		float accumulator = 0.0;
 		double currentTime;
 		double t = 0.0;
 		double dt = 0.01;
-		state previous;
 };
diff --git a/gameloop/include/timer.h b/gameloop/include/timer.h
index 2769e4d..a245e5c 100644
--- a/gameloop/include/timer.h
+++ b/gameloop/include/timer.h
@@ -7,25 +7,24 @@ public:
     static LoopTimer& getInstance();
     void start();
     void update();
-    float getDeltaTime() const;
-	float getDeltaTimeMs() const;
-	float getFixedDeltaTime() const;
+    double getDeltaTime() const;
     int getCurrentTime() const;
+	void advanceFixedUpdate();
+	double getFixedDeltaTime() const;
     void setFPS(int FPS);
     int getFPS() const;
     void enforceFrameRate();
-	float getLag() const;
+	double getLag() const;
 private:
     LoopTimer();
-	int FPS = 30;
-	float frameTargetTime = FPS / 1000;
-    int lastTime;
-	float fixedDeltaTime = 2;
-	float maxDeltaTime = 1;
-	float fixedTime = 0;
-    int lastFrameTime;
-    float deltaTime;
-	float time = 0;
-    int frequency;
-	float lag;
+	int FPS = 50;
+	double gameScale = 1;
+	double maximumDeltaTime = 0.25;
+    double deltaTime;
+	double frameTargetTime = FPS / 1000;
+    double fixedDeltaTime = 0.01;
+    double elapsedTime;
+    double elapsedFixedTime;
+	double time;
+    uint64_t lastFrameTime;
 };
diff --git a/gameloop/src/loopManager.cpp b/gameloop/src/loopManager.cpp
index c439a3e..f7ce886 100644
--- a/gameloop/src/loopManager.cpp
+++ b/gameloop/src/loopManager.cpp
@@ -19,24 +19,28 @@ void LoopManager::processInput(){
 void LoopManager::fixedUpdate(){
 	fprintf(stderr,"fixed update\n");
 }
-void LoopManager::loop(){
-	fprintf(stderr,"loop. \n");
-	LoopTimer& timer = LoopTimer::getInstance();
-	while(gameRunning){
-		timer.update();
-		lag += timer.getDeltaTime();
-		processInput();
-		while (lag >= timer.getFixedDeltaTime())
-		{
-			fixedUpdate();
-			lag -= timer.getFixedDeltaTime();
-		}
-		//update();
-		//timer.enforceFrameRate();
-		render();
-	}
-	window.destroyWindow();
+void LoopManager::loop() {
+    LoopTimer& timer = LoopTimer::getInstance();
+    timer.start();
+
+    while (gameRunning) {
+        timer.update();
+
+        while (timer.getLag() >= timer.getFixedDeltaTime()) {
+            processInput();
+            fixedUpdate();
+            timer.advanceFixedUpdate();
+        }
+
+        update();
+        render();
+
+        timer.enforceFrameRate();
+    }
+
+    window.destroyWindow();
 }
+
 void LoopManager::setup(){
 	gameRunning = window.initWindow();
 	LoopTimer::getInstance().start();
diff --git a/gameloop/src/timer.cpp b/gameloop/src/timer.cpp
index 6428797..1e3045f 100644
--- a/gameloop/src/timer.cpp
+++ b/gameloop/src/timer.cpp
@@ -1,56 +1,68 @@
 #include "timer.h"
 
-// Singleton instance for global access
+// Constructor (private)
+LoopTimer::LoopTimer(){}
+
+// Get the singleton instance of the timer
 LoopTimer& LoopTimer::getInstance() {
     static LoopTimer instance;
     return instance;
 }
 
-// Private constructor
-LoopTimer::LoopTimer() : lastTime(0), deltaTime(0), frequency(0), FPS(0), frameTargetTime(0) {}
-
+// Start the timer (initialize frame time)
 void LoopTimer::start() {
-
+    lastFrameTime = SDL_GetTicks64();
+    elapsedTime = 0;
+    elapsedFixedTime = 0;
+    deltaTime = 0;
 }
 
+// Update the timer, calculate deltaTime
 void LoopTimer::update() {
-    Uint64 currentTime = SDL_GetTicks64();
-    deltaTime = (currentTime - lastFrameTime) / 1000.0;
-	time += deltaTime;
-    lastFrameTime = currentTime;
+    uint64_t currentFrameTime = SDL_GetTicks64();
+    deltaTime = (currentFrameTime - lastFrameTime) / 1000.0;  // Convert to seconds
+
+    if (deltaTime > maximumDeltaTime) {
+        deltaTime = maximumDeltaTime;
+    }
+
+    elapsedTime += deltaTime;
+    lastFrameTime = currentFrameTime;
 }
 
-float LoopTimer::getDeltaTime() const {
+double LoopTimer::getDeltaTime() const {
     return deltaTime;
 }
-float LoopTimer::getDeltaTimeMs() const {
-    return deltaTime * 1000;
-}
 int LoopTimer::getCurrentTime() const {
-    return SDL_GetTicks64();
+    return SDL_GetTicks();
 }
 
-float LoopTimer::getFixedDeltaTime() const {
+void LoopTimer::advanceFixedUpdate() {
+    elapsedFixedTime += fixedDeltaTime;
+}
+
+double LoopTimer::getFixedDeltaTime() const {
     return fixedDeltaTime;
 }
 
 void LoopTimer::setFPS(int FPS) {
-    if (FPS > 0) {
-        this->FPS = FPS;
-        frameTargetTime = 1000 / FPS;
-    }
-}
-float LoopTimer::getLag() const{
-	return lag;
+    this->FPS = FPS;
+    frameTargetTime = 1.0 / FPS;
 }
+
 int LoopTimer::getFPS() const {
     return FPS;
 }
 
-// Delay to match target frame time
 void LoopTimer::enforceFrameRate() {
-    int waitTime = frameTargetTime - (SDL_GetTicks64() - lastFrameTime);
-	if(waitTime > 0 && waitTime <= frameTargetTime){
-		SDL_Delay(waitTime);
-	}
+    uint64_t currentFrameTime = SDL_GetTicks64();
+    double frameDuration = (currentFrameTime - lastFrameTime) / 1000.0;
+
+    if (frameDuration < frameTargetTime) {
+        uint32_t delayTime = (uint32_t)((frameTargetTime - frameDuration) * 1000.0);
+        SDL_Delay(delayTime);
+    }
+}
+double LoopTimer::getLag() const {
+    return elapsedTime - elapsedFixedTime;
 }
-- 
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