Create empty game window

app/src/main/java/com/bartlomiejpluta/samplegame/App.java

@@ -3,20 +3,25 @@
  */
 package com.bartlomiejpluta.samplegame;
 
+import com.bartlomiejpluta.samplegame.core.engine.GameEngine;
+import lombok.RequiredArgsConstructor;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.ApplicationArguments;
 import org.springframework.boot.ApplicationRunner;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 
 @SpringBootApplication
+@RequiredArgsConstructor(onConstructor = @__(@Autowired))
 public class App implements ApplicationRunner {
+    private final GameEngine gameEngine;
+
+    @Override
+    public void run(ApplicationArguments args) {
+        gameEngine.start();
+    }
 
     public static void main(String[] args) {
         SpringApplication.run(App.class, args);
     }
-
-    @Override
-    public void run(ApplicationArguments args) {
-
-    }
 }

app/src/main/java/com/bartlomiejpluta/samplegame/core/engine/DefaultGameEngine.java

@@ -0,0 +1,95 @@
+package com.bartlomiejpluta.samplegame.core.engine;
+
+import com.bartlomiejpluta.samplegame.core.thread.ThreadManager;
+import com.bartlomiejpluta.samplegame.core.time.ChronoMeter;
+import com.bartlomiejpluta.samplegame.core.ui.Window;
+import com.bartlomiejpluta.samplegame.core.ui.WindowManager;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+
+@Component
+public class DefaultGameEngine implements GameEngine {
+   private final WindowManager windowManager;
+   private final ThreadManager threadManager;
+
+   private final Thread thread;
+   private final Window window;
+   private final ChronoMeter chrono;
+   private final int targetUps;
+
+   private boolean running = false;
+
+   @Autowired
+   public DefaultGameEngine(WindowManager windowManager,
+                            ThreadManager threadManager,
+                            @Value("${app.window.title}") String title,
+                            @Value("${app.window.width}") int width,
+                            @Value("${app.window.height}") int height,
+                            @Value("${app.core.targetUps}") int targetUps) {
+      this.windowManager = windowManager;
+      this.threadManager = threadManager;
+
+
+      this.window = windowManager.createWindow(title, width, height);
+      this.thread = threadManager.createThread(this::run);
+      this.chrono = new ChronoMeter();
+      this.targetUps = targetUps;
+   }
+
+   private void run() {
+      try {
+         init();
+         loop();
+      } finally {
+         cleanUp();
+      }
+   }
+
+   private void init() {
+      window.init();
+      chrono.init();
+   }
+
+   private void loop() {
+      running = true;
+      var dt = 0.0f;
+      var accumulator = 0.0f;
+      var step = 1.0f / targetUps;
+
+      while (running && !window.shouldClose()) {
+         dt = chrono.getElapsedTime();
+         accumulator += dt;
+
+         input();
+
+         while (accumulator >= step) {
+            update(dt);
+            accumulator -= step;
+         }
+
+         render();
+      }
+   }
+
+   private void input() {
+
+   }
+
+   private void update(float dt) {
+
+   }
+
+   private void render() {
+      window.update();
+   }
+
+   private void cleanUp() {
+
+   }
+
+   @Override
+   public void start() {
+      thread.start();
+   }
+}

app/src/main/java/com/bartlomiejpluta/samplegame/core/engine/GameEngine.java

@@ -0,0 +1,5 @@
+package com.bartlomiejpluta.samplegame.core.engine;
+
+public interface GameEngine {
+   void start();
+}

app/src/main/java/com/bartlomiejpluta/samplegame/core/error/AppException.java

@@ -0,0 +1,22 @@
+package com.bartlomiejpluta.samplegame.core.error;
+
+public class AppException extends RuntimeException {
+   public AppException() {
+   }
+
+   public AppException(String message) {
+      super(message);
+   }
+
+   public AppException(String message, Throwable cause) {
+      super(message, cause);
+   }
+
+   public AppException(Throwable cause) {
+      super(cause);
+   }
+
+   public AppException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
+      super(message, cause, enableSuppression, writableStackTrace);
+   }
+}

app/src/main/java/com/bartlomiejpluta/samplegame/core/thread/ThreadManager.java

@@ -0,0 +1,10 @@
+package com.bartlomiejpluta.samplegame.core.thread;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class ThreadManager {
+   public Thread createThread(Runnable runnable) {
+      return new Thread(runnable);
+   }
+}

app/src/main/java/com/bartlomiejpluta/samplegame/core/time/ChronoMeter.java

@@ -0,0 +1,20 @@
+package com.bartlomiejpluta.samplegame.core.time;
+
+public class ChronoMeter {
+   private double latchedTime;
+
+   public void init() {
+      latchedTime = getTime();
+   }
+
+   private double getTime() {
+      return System.nanoTime() / 1_000_000_000.0;
+   }
+
+   public float getElapsedTime() {
+      double time = getTime();
+      float elapsedTime = (float) (time - latchedTime);
+      latchedTime = time;
+      return elapsedTime;
+   }
+}

app/src/main/java/com/bartlomiejpluta/samplegame/core/ui/Window.java

@@ -0,0 +1,107 @@
+package com.bartlomiejpluta.samplegame.core.ui;
+
+import com.bartlomiejpluta.samplegame.core.error.AppException;
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import org.lwjgl.glfw.GLFWErrorCallback;
+import org.lwjgl.glfw.GLFWVidMode;
+import org.lwjgl.opengl.GL;
+
+import static org.lwjgl.glfw.GLFW.*;
+import static org.lwjgl.opengl.GL11.*;
+import static org.lwjgl.opengl.GL11.GL_DEPTH_TEST;
+import static org.lwjgl.system.MemoryUtil.NULL;
+
+@AllArgsConstructor(access = AccessLevel.PRIVATE)
+public class Window {
+   private final String title;
+   private int width;
+   private int height;
+   private long windowHandle;
+   private boolean resized;
+
+   public void init() {
+      // Setup an error callback. The default implementation
+      // will print the error message in System.err.
+      GLFWErrorCallback.createPrint(System.err).set();
+
+      // Initialize GLFW. Most GLFW functions will not work before doing this.
+      if (!glfwInit()) {
+         throw new AppException("Unable to initialize GLFW");
+      }
+
+      glfwDefaultWindowHints(); // optional, the current window hints are already the default
+      glfwWindowHint(GLFW_VISIBLE, GL_FALSE); // the window will stay hidden after creation
+      glfwWindowHint(GLFW_RESIZABLE, GL_TRUE); // the window will be resizable
+      glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
+      glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
+      glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+      glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
+
+      // Create the window
+      windowHandle = glfwCreateWindow(width, height, title, NULL, NULL);
+      if (windowHandle == NULL) {
+         throw new AppException("Failed to create the GLFW window");
+      }
+
+      // Setup resize callback
+      glfwSetFramebufferSizeCallback(windowHandle, (window, width, height) -> {
+         Window.this.width = width;
+         Window.this.height = height;
+         Window.this.resized = true;
+      });
+
+      // Setup a key callback. It will be called every time a key is pressed, repeated or released.
+      glfwSetKeyCallback(windowHandle, (window, key, scancode, action, mods) -> {
+         if (key == GLFW_KEY_ESCAPE && action == GLFW_RELEASE) {
+            glfwSetWindowShouldClose(window, true); // We will detect this in the rendering loop
+         }
+      });
+
+      // Get the resolution of the primary monitor
+      GLFWVidMode videoMode = glfwGetVideoMode(glfwGetPrimaryMonitor());
+
+      // Center our window
+      glfwSetWindowPos(windowHandle, (videoMode.width() - width) / 2, (videoMode.height() - height) / 2);
+
+      // Make the OpenGL context current
+      glfwMakeContextCurrent(windowHandle);
+
+      // Enable V-Sync
+      glfwSwapInterval(1);
+
+      // Make the window visible
+      glfwShowWindow(windowHandle);
+
+      GL.createCapabilities();
+
+      // Support for transparencies
+      glEnable(GL_BLEND);
+      glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+      // Set the clear color
+      glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+      glEnable(GL_DEPTH_TEST);
+   }
+
+   public void update() {
+      glfwSwapBuffers(windowHandle);
+      glfwPollEvents();
+   }
+
+   public boolean isKeyPressed(int keyCode) {
+      return glfwGetKey(windowHandle, keyCode) == GLFW_PRESS;
+   }
+
+   public void clear(float r, float g, float b, float alpha) {
+      glClearColor(r, g, b, alpha);
+   }
+
+   public boolean shouldClose() {
+      return glfwWindowShouldClose(windowHandle);
+   }
+
+   public static Window create(String title, int width, int height) {
+      return new Window(title, width, height, -1, false);
+   }
+}

app/src/main/java/com/bartlomiejpluta/samplegame/core/ui/WindowManager.java

@@ -0,0 +1,10 @@
+package com.bartlomiejpluta.samplegame.core.ui;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class WindowManager {
+   public Window createWindow(String title, int width, int height) {
+      return Window.create(title, width, height);
+   }
+}

app/src/main/resources/application.yml

@@ -0,0 +1,8 @@
+app:
+  window:
+    title: "Simple Game"
+    width: 640
+    height: 480
+
+  core:
+    targetUps: 50 # Updates per second

app/src/test/java/com/bartlomiejpluta/samplegame/AppTest.java

@@ -1,14 +0,0 @@
-/*
- * This Java source file was generated by the Gradle 'init' task.
- */
-package com.bartlomiejpluta.samplegame;
-
-import org.junit.Test;
-import static org.junit.Assert.*;
-
-public class AppTest {
-    @Test public void testAppHasAGreeting() {
-        App classUnderTest = new App();
-        assertNotNull("app should have a greeting", classUnderTest.getGreeting());
-    }
-}