com.acornui.jvm.LwjglHelloWorld.java Source code

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Here is the source code for com.acornui.jvm.LwjglHelloWorld.java

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/*
 * Copyright 2019 Poly Forest, LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.acornui.jvm;

import org.lwjgl.Version;
import org.lwjgl.glfw.GLFWErrorCallback;
import org.lwjgl.glfw.GLFWVidMode;
import org.lwjgl.opengl.GL;
import org.lwjgl.opengl.GL11;
import org.lwjgl.system.MemoryStack;

import java.nio.IntBuffer;

import static org.lwjgl.glfw.Callbacks.glfwFreeCallbacks;
import static org.lwjgl.glfw.GLFW.*;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.system.MemoryStack.stackPush;
import static org.lwjgl.system.MemoryUtil.NULL;

public class LwjglHelloWorld {

    // 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");

        // 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.

        initMatrices();

        while (!glfwWindowShouldClose(window)) {
            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear the framebuffer

            draw();

            glfwSwapBuffers(window); // swap the color buffers

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

    private void initMatrices() {
        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0, 800, 0, 600, 1, -1);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
    }

    private void draw() {
        // set the color of the quad (R,G,B,A)
        GL11.glColor3f(0.5f, 0.5f, 1.0f);

        // draw quad
        GL11.glBegin(GL11.GL_QUADS);
        GL11.glVertex2f(100, 100);
        GL11.glVertex2f(100 + 200, 100);
        GL11.glVertex2f(100 + 200, 100 + 200);
        GL11.glVertex2f(100, 100 + 200);
        GL11.glEnd();
    }

    public static void main(String[] args) {
        new LwjglHelloWorld().run();
    }

}