lightweight java game library

1import org.lwjgl.*;
2import org.lwjgl.glfw.*;
3import org.lwjgl.opengl.*;
4import org.lwjgl.system.*;
5
6import java.nio.*;
7
8import static org.lwjgl.glfw.Callbacks.*;
9import static org.lwjgl.glfw.GLFW.*;
10import static org.lwjgl.opengl.GL11.*;
11import static org.lwjgl.system.MemoryStack.*;
12import static org.lwjgl.system.MemoryUtil.*;
13
14public class HelloWorld {
15
16	// The window handle
17	private long window;
18
19	public void run() {
20		System.out.println("Hello LWJGL " + Version.getVersion() + "!");
21
22		init();
23		loop();
24
25		// Free the window callbacks and destroy the window
26		glfwFreeCallbacks(window);
27		glfwDestroyWindow(window);
28
29		// Terminate GLFW and free the error callback
30		glfwTerminate();
31		glfwSetErrorCallback(null).free();
32	}
33
34	private void init() {
35		// Setup an error callback. The default implementation
36		// will print the error message in System.err.
37		GLFWErrorCallback.createPrint(System.err).set();
38
39		// Initialize GLFW. Most GLFW functions will not work before doing this.
40		if ( !glfwInit() )
41			throw new IllegalStateException("Unable to initialize GLFW");
42
43		// Configure GLFW
44		glfwDefaultWindowHints(); // optional, the current window hints are already the default
45		glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE); // the window will stay hidden after creation
46		glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE); // the window will be resizable
47
48		// Create the window
49		window = glfwCreateWindow(300, 300, "Hello World!", NULL, NULL);
50		if ( window == NULL )
51			throw new RuntimeException("Failed to create the GLFW window");
52
53		// Setup a key callback. It will be called every time a key is pressed, repeated or released.
54		glfwSetKeyCallback(window, (window, key, scancode, action, mods) -> {
55			if ( key == GLFW_KEY_ESCAPE && action == GLFW_RELEASE )
56				glfwSetWindowShouldClose(window, true); // We will detect this in the rendering loop
57		});
58
59		// Get the thread stack and push a new frame
60		try ( MemoryStack stack = stackPush() ) {
61			IntBuffer pWidth = stack.mallocInt(1); // int*
62			IntBuffer pHeight = stack.mallocInt(1); // int*
63
64			// Get the window size passed to glfwCreateWindow
65			glfwGetWindowSize(window, pWidth, pHeight);
66
67			// Get the resolution of the primary monitor
68			GLFWVidMode vidmode = glfwGetVideoMode(glfwGetPrimaryMonitor());
69
70			// Center the window
71			glfwSetWindowPos(
72				window,
73				(vidmode.width() - pWidth.get(0)) / 2,
74				(vidmode.height() - pHeight.get(0)) / 2
75			);
76		} // the stack frame is popped automatically
77
78		// Make the OpenGL context current
79		glfwMakeContextCurrent(window);
80		// Enable v-sync
81		glfwSwapInterval(1);
82
83		// Make the window visible
84		glfwShowWindow(window);
85	}
86
87	private void loop() {
88		// This line is critical for LWJGL's interoperation with GLFW's
89		// OpenGL context, or any context that is managed externally.
90		// LWJGL detects the context that is current in the current thread,
91		// creates the GLCapabilities instance and makes the OpenGL
92		// bindings available for use.
93		GL.createCapabilities();
94
95		// Set the clear color
96		glClearColor(1.0f, 0.0f, 0.0f, 0.0f);
97
98		// Run the rendering loop until the user has attempted to close
99		// the window or has pressed the ESCAPE key.
100		while ( !glfwWindowShouldClose(window) ) {
101			glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear the framebuffer
102
103			glfwSwapBuffers(window); // swap the color buffers
104
105			// Poll for window events. The key callback above will only be
106			// invoked during this call.
107			glfwPollEvents();
108		}
109	}
110
111	public static void main(String[] args) {
112		new HelloWorld().run();
113	}
114
115}