Lwjgl 3, How to get OpenGL context current in the current thread?

问题

I am using OpenGL in LWJGL 3 and I get the following error;

Exception in thread "main" java.lang.IllegalStateException: There is no OpenGL context current in the current thread. at org.lwjgl.opengl.GL.getCapabilities(GL.java:157) at org.lwjgl.opengl.GL11.getInstance(GL11.java:1390) at org.lwjgl.opengl.GL11.glClearColor(GL11.java:1842) at com.base.engine.RenderUtil.initGraphics(RenderUtil.java:13) at com.base.engine.Main.<init>(Main.java:14) at com.base.engine.Main.main(Main.java:24)

This is the RenderUtil class where initGraphics is called from the constructor of my main class. I have also tried to call initGraphics after creating a window with GLFW which has also generated a similar error message.

package com.base.engine;

import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL30.*;

public class RenderUtil {

    public static void clearScreen() {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    }

    public static void initGraphics() {
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

        glFrontFace(GL_CW);
        glCullFace(GL_BACK);
        glEnable(GL_CULL_FACE);
        glEnable(GL_DEPTH_TEST);

        glEnable(GL_FRAMEBUFFER_SRGB);
    }
}

Also, I am not using multithreading. To create a window I call the method Window.createWindow(1366, 768, "Test"); from my main method.

    private static Long window;

    public static String createWindow(int width, int height, String title) {
        if (GLFW.glfwInit() == 0) {
            return "GLFW failed to initialise.";
        }

        GLFW.glfwWindowHint(GLFW.GLFW_SAMPLES, 4);
        window = GLFW.glfwCreateWindow(width, height, title,
                GLFW.glfwGetPrimaryMonitor(), 0);

        if (window == null) {
            GLFW.glfwTerminate();
            return "Failed to create window.";
        }

        GLFW.glfwMakeContextCurrent(window);
        return "GLFW has established a window.";
    }

I have tried putting RenderUtil.initGraphics(); two different position in my main method, both resulting in errors.

    private boolean isRunning = false;
    private Game game;


    // This is the constructor
    public Main() {
        // Pos 1 - RenderUtil.initGraphics();
        isRunning = false;
        game = new Game();
    }

    public static void main(String[] args) {
        System.out.println(Window.createWindow(1366, 768, "Test"));
        // Pos 2 - RenderUtil.initGraphics();
        Main game = new Main();
        game.start();
    }

回答1:

Add a call to GLContext.createFromCurrent() at the end of the createWindow method.

This method is needed to set the context used by the LWJGL GL** classes under the hood.

EDIT:

Since the latest nightly (3.0.0b #11) this no longer works, as the GLContext class no more exists. Instead, add GL.createCapabilities() at the end of the createWindow method.

回答2:

I know that this thread is 4 years old but if someone of you still needs a solution here you go:

import org.lwjgl.glfw.*;
import org.lwjgl.opengl.*;

public class Main {
private static long window = 0;

public static void main(String[] args) {
    if(!GLFW.glfwInit()) {
        throw new RuntimeException("Cannot initialize OPenGL");
    }

    window = GLFW.glfwCreateWindow(1024, 764, "Ya yeet", 0, 0);
    if(0 == window) {
        GLFW.glfwTerminate();
        throw new RuntimeException("Cannot create window");
    }

    GLFW.glfwMakeContextCurrent(window);
    GL.createCapabilities();

    String glVersion = GL11.glGetString(GL11.GL_VERSION);
    System.out.println(glVersion);
}
}

回答3:

To init and use LWJGL 3 you need to do next (code in Kotlin):

import org.lwjgl.glfw.GLFW
import org.lwjgl.opengl.GL
import org.lwjgl.opengl.GL11
import org.lwjgl.system.MemoryUtil.NULL


class VersionInfo {

    var window: Long = NULL

    fun run() {
        initGl()

        // use openGL
        val glVersion = GL11.glGetString(GL11.GL_VERSION)
        println("GL version: $glVersion")
    }

    private fun initGl() {
        // check GLFW
        if (!GLFW.glfwInit()) {
            throw IllegalStateException("Can not initialize GLFW")
        }
        // create window
        window = GLFW.glfwCreateWindow(1024, 764, "glfw", NULL, NULL)
        // check window
        if (NULL == window) {
            GLFW.glfwTerminate()
            throw IllegalStateException("Can not create new GLFW window")
        }
        // make GL context in the current thread
        GLFW.glfwMakeContextCurrent(window)
        // create capabilities
        GL.createCapabilities()
    }

    companion object {
        @JvmStatic
        fun main(args: Array<String>) {
            VersionInfo().run()
        }
    }
}

For more information, please, see official get-started guide: http://www.lwjgl.org/guide
Or Wiki: https://github.com/LWJGL/lwjgl3-wiki/wiki

来源：https://stackoverflow.com/questions/27659729/lwjgl-3-how-to-get-opengl-context-current-in-the-current-thread