snuvi-engine/src/me/hammerle/snuviengine/api/Window.java

package me.hammerle.snuviengine.api;

import org.lwjgl.glfw.*;
import org.lwjgl.opengl.*;
import static org.lwjgl.glfw.GLFW.*;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.system.MemoryUtil.*;

public final class Window {
    private final double secondsPerTick;
    private long window = NULL;
    private Keys keys = null;
    private Gamepad gamepad = null;
    private Renderer renderer;
    private final Stats stats = new Stats();

    public Window(long nanosPerTick) {
        secondsPerTick = nanosPerTick / 1_000_000_000.0;
    }

    public boolean initialize(String name, int width, int height) {
        setErrorCallback();
        if(initializeGLFW()) {
            return false;
        }
        setWindowHints();
        if(createWindow(name, width, height)) {
            return false;
        }
        setKeyCallback();
        setGamepad();
        setResizeCallback();
        createAndSetContext();
        setBufferSwapInterval();
        return !initializeRenderer(width, height);
    }

    private void setErrorCallback() {
        GLFWErrorCallback.createPrint(System.out).set();
    }

    private boolean initializeGLFW() {
        return !glfwInit();
    }

    private void setWindowHints() {
        glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
        glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
        glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    }

    private boolean createWindow(String name, int width, int height) {
        window = glfwCreateWindow(width, height, name, NULL, NULL);
        if(window == NULL) {
            terminateGLFW();
            return true;
        }
        return false;
    }

    private void terminateGLFW() {
        glfwTerminate();
    }

    private void setKeyCallback() {
        keys = new Keys();
        glfwSetKeyCallback(window, (eventWindow, key, scancode, action, mods) -> {
            if(action == GLFW_PRESS) {
                keys.press(key);
            } else if(action == GLFW_RELEASE) {
                keys.release(key);
            }
        });
    }

    private void setGamepad() {
        gamepad = new Gamepad(GLFW_JOYSTICK_1);
    }

    private void setResizeCallback() {
        glfwSetFramebufferSizeCallback(window, (eventWindow, width, height) -> {
            glViewport(0, 0, width, height);
            renderer.setSize(width, height);
        });
    }

    private void createAndSetContext() {
        glfwMakeContextCurrent(window);
        GL.createCapabilities();
    }

    private void setBufferSwapInterval() {
        glfwSwapInterval(1);
    }

    private boolean initializeRenderer(int width, int height) {
        int shaderProgram = Shader.createShaderProgram("vertex.vs", "fragment.fs");
        if(shaderProgram == -1) {
            return true;
        }
        renderer = new Renderer(shaderProgram, width, height);
        return false;
    }

    public void open(Game game) {
        game.onCompleteInitialization(stats, keys, gamepad);
        runGameLoop(game);
        game.onStop();
        destroyWindow();
        terminateGLFW();
        freeErrorCallback();
    }

    private void runGameLoop(Game game) {
        double lastSecondTime = glfwGetTime();
        double lag = 0;
        while(!glfwWindowShouldClose(window) && game.isRunning()) {
            double newSecondTime = glfwGetTime();
            lag += newSecondTime - lastSecondTime;
            lastSecondTime = newSecondTime;
            while(lag >= secondsPerTick) {
                lag -= secondsPerTick;
                tick(game);
            }
            renderTick(game, (float) (lag / secondsPerTick));
        }
    }

    private void tick(Game game) {
        stats.updateTicksPerSecond();
        gamepad.tick();
        keys.tick();
        game.tick();
    }

    private void renderTick(Game game, float lag) {
        stats.updateFramesPerSecond();
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        game.renderTick(renderer, lag);
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    private void destroyWindow() {
        glfwDestroyWindow(window);
    }

    private void freeErrorCallback() {
        GLFWErrorCallback error = glfwSetErrorCallback(null);
        if(error != null) {
            error.free();
        }
    }
}