LWJGL教程01 - 创建窗口

从示范代码到Window类

先来看实例代码：

[imports ...]

public class HelloWorld {

	// The window handle
	private long window;

	public void run() {
		System.out.println("Hello LWJGL " + Version.getVersion() + "!");

		init();
		loop();

		// Free the window callbacks and destroy the window
		glfwFreeCallbacks(window);
		glfwDestroyWindow(window);

		// Terminate GLFW and free the error callback
		glfwTerminate();
		glfwSetErrorCallback(null).free();
	}

	private 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 IllegalStateException("Unable to initialize GLFW");

		// Configure GLFW
		glfwDefaultWindowHints(); // optional, the current window hints are already the default
		glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE); // the window will stay hidden after creation
		glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE); // the window will be resizable

		// Create the window
		window = glfwCreateWindow(300, 300, "Hello World!", NULL, NULL);
		if ( window == NULL )
			throw new RuntimeException("Failed to create the GLFW window");

		// Setup a key callback. It will be called every time a key is pressed, repeated or released.
		glfwSetKeyCallback(window, (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 thread stack and push a new frame
		try ( MemoryStack stack = stackPush() ) {
			IntBuffer pWidth = stack.mallocInt(1); // int*
			IntBuffer pHeight = stack.mallocInt(1); // int*

			// Get the window size passed to glfwCreateWindow
			glfwGetWindowSize(window, pWidth, pHeight);

			// Get the resolution of the primary monitor
			GLFWVidMode vidmode = glfwGetVideoMode(glfwGetPrimaryMonitor());

			// Center the window
			glfwSetWindowPos(
				window,
				(vidmode.width() - pWidth.get(0)) / 2,
				(vidmode.height() - pHeight.get(0)) / 2
			);
		} // the stack frame is popped automatically

		// Make the OpenGL context current
		glfwMakeContextCurrent(window);
		// Enable v-sync
		glfwSwapInterval(1);

		// Make the window visible
		glfwShowWindow(window);
	}

	private void loop() {
		// This line is critical for LWJGL's interoperation with GLFW's
		// OpenGL context, or any context that is managed externally.
		// LWJGL detects the context that is current in the current thread,
		// creates the GLCapabilities instance and makes the OpenGL
		// bindings available for use.
		GL.createCapabilities();

		// Set the clear color
		glClearColor(1.0f, 0.0f, 0.0f, 0.0f);

		// Run the rendering loop until the user has attempted to close
		// the window or has pressed the ESCAPE key.
		while ( !glfwWindowShouldClose(window) ) {
			glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear the framebuffer

			glfwSwapBuffers(window); // swap the color buffers

			// Poll for window events. The key callback above will only be
			// invoked during this call.
			glfwPollEvents();
		}
	}

	[main ...]

}

虽然不多，但初见着实让人有点头晕。

将整个程序归纳为：

[init ...]
while(!glfwWindowShouldClose(window)) {
    [do something ...]
}
[close ...]

Window类的工作大致就是实现init()的内容。

为了能够自定义窗口的各种属性，在Window类中创建一个内部类Settings来存储相关参数。

public static class Settings {
    public int width;
    public int height;
    public String ztitle;
    public boolean vsync = false;
    public float[] color = new float[4];
    public Callable resizeCallback = () -> null;
    
    [Setter & Getter ...]
}

然后将示例代码终端init()提取出来，并将width，height，title替换进去。

[imports ...]

public class Window {
    [Settings]

    public static long window;
    public static Settings settings;

    public static void createWindow(Settings settings) {
        Window.settings = settings;
		
        [...]
        
        // Create the window
        window = glfwCreateWindow(settings.width, settings.height, settings.title, NULL, NULL);
        
        [...]
        
        // Enable v-sync
        glfwSwapInterval(0);
        if(settings.vsync)
            glfwSwapInterval(1);
        
        glfwSetFramebufferSizeCallback(window, (window, width, height) -> {
            Window.width = width;
            Window.height = height;
            try {
                settings.resizeCallback.call();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        });
        
        GL.createCapabilities();
    }
    
    public static boolean windowShouldClose() {
        return glfwWindowShouldClose(window);
    }
    
    public static void pollEvents() {
        glfwPollEvents();
    }

    public static void cleanup() {
        // Free the window callbacks and destroy the window
        glfwFreeCallbacks(window);
        glfwDestroyWindow(window);

        // Terminate GLFW and free the error callback
        glfwTerminate();
        glfwSetErrorCallback(null).free();
    }
    
    public static void setWindowVisible() {
        glfwShowWindow(window);
    }
    
    public static boolean isKeyPressed(int keyCode) {
        return glfwGetKey(window, keyCode) == GLFW_PRESS;
    }
}

现在测试一下Window类。

[imports ...]

public class TestWindow {
    public static void main(String[] args) {
        Window.Settings settings = new Window.Settings();
        settings.width = 800;
        settings.height = 600;
        settings.title = "Test Window";
        Window.createWindow(settings);
        Window.setWindowVisible();
        while (!Window.windowShouldClose())
            Window.pollEvents();
        Window.cleanup();
    }
}