Add engine manager class to handle non window stuff.

src/main/java/com/okseby/core/EngineManager.java

@@ -0,0 +1,112 @@
+package com.okseby.core;
+
+import com.okseby.core.utils.Constants;
+import org.lwjgl.glfw.GLFW;
+import org.lwjgl.glfw.GLFWErrorCallback;
+
+public class EngineManager {
+    public static final long NANOSECOND = 1000000000;
+    public static final float FRAMERATE = 1000;
+
+    private static int fps;
+    private static float frametime = 1.0f / FRAMERATE;
+
+    private boolean isRunning;
+
+    private WindowManager window;
+    private GLFWErrorCallback errorCallback;
+
+    private void init() throws Exception {
+        GLFW.glfwSetErrorCallback(errorCallback = GLFWErrorCallback.createPrint(System.err));
+        window = Launcher.getWindow();
+        window.init();
+    }
+
+    public void start() throws Exception {
+        init();
+
+        if (isRunning)
+            return;
+
+        run();
+    }
+
+    public void run() {
+        this.isRunning = true;
+
+        int frames = 0;
+        long frameCounter = 0;
+        long lastTime = System.nanoTime();
+        double unprocessedTime = 0;
+
+        while (isRunning) {
+            boolean render = false;
+            long startTime = System.nanoTime();
+            long passedTime = startTime - lastTime;
+
+            lastTime = startTime;
+            unprocessedTime += passedTime / (double) NANOSECOND;
+            frameCounter += passedTime;
+
+            input();
+
+            while (unprocessedTime > frametime) {
+                render = true;
+                unprocessedTime -= frametime;
+
+                if (window.windowShouldClose())
+                    stop();
+
+                if (frameCounter >= NANOSECOND) {
+                    setFps(frames);
+
+                    window.setTitle(Constants.title + " - FPS: " + getFps());
+
+                    frames = 0;
+                    frameCounter = 0;
+                }
+            }
+
+            if (render) {
+                update();
+                render();
+                frames++;
+            }
+        }
+
+        cleanup();
+    }
+
+    private void stop() {
+        if (!isRunning)
+            return;
+        isRunning = false;
+    }
+
+    private void input() {
+
+    }
+
+    private void render() {
+        window.update();
+    }
+
+    private void update() {
+
+    }
+
+    private void cleanup() {
+        window.cleanup();
+        errorCallback.free();
+
+        GLFW.glfwTerminate();
+    }
+
+    public static int getFps() {
+        return fps;
+    }
+
+    public static void setFps(int fps) {
+        EngineManager.fps = fps;
+    }
+}

src/main/java/com/okseby/core/Launcher.java

@@ -1,17 +1,27 @@
 package com.okseby.core;
 
+import com.okseby.core.utils.Constants;
 import org.lwjgl.Version;
 
 public class Launcher {
+
+    private static WindowManager window;
+    private static EngineManager engine;
+
     public static void main(String[] args) {
         System.out.println("LWJGL Version: " + Version.getVersion());
 
-        WindowManager window = new WindowManager("Warabi Engine", 1600, 900, false);
+        window = new WindowManager(Constants.title, 1600, 900, false);
-        window.init();
+        engine = new EngineManager();
 
-        while (!window.windowShouldClose())
+        try {
-            window.update();
+            engine.start();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
 
-        window.cleanup();
+    public static WindowManager getWindow() {
+        return window;
     }
 }

src/main/java/com/okseby/core/utils/Constants.java

@@ -0,0 +1,5 @@
+package com.okseby.core.utils;
+
+public class Constants {
+    public static final String title = "Warabi Engine";
+}