Very simple program returns GLEW_ERROR_NO_GLX_DISPLAY

[wbehrens-on-gh]

Here's the program:

#include <GL/glew.h>
#include <GLFW/glfw3.h>

#include <iostream>

int main(void) {
    /* Initialize the library */
    if (!glfwInit()) { 
        return -1; 
    }

    /* Create a windowed mode window and its OpenGL context */
    GLFWwindow* window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
    if (!window) {
        glfwTerminate();
        return -1;
    }

    /* Make the window's context current */
    glfwMakeContextCurrent(window);

    /* Initialize glew for cross-platform opengl */
    if(GLenum state = glewInit(); state != GLEW_OK) { 
        std::cerr << "Error: glewInit() returned " << state << std::endl;
        return state; 
    }

    std::cout << glGetString(GL_VERSION) << std::endl;

    /* Loop until the user closes the window */
    while (!glfwWindowShouldClose(window)) {
        /* Render here */
        glClear(GL_COLOR_BUFFER_BIT);

        /* Swap front and back buffers */
        glfwSwapBuffers(window);

        /* Poll for and process events */
        glfwPollEvents();
    }

    glfwTerminate();
    return 0;
}

It should error on glewInit() and print 4, which as far as I can tell is GLEW_ERROR_NO_GLX_DISPLAY, I'm very new to opengl so there's a good change I've done something wrong but if it makes any difference I'm currently running this on a wayland based desktop enviroment.

[nigels-com]

Out of interest, what Linux distro and GPU and driver combo is running?

[wbehrens-on-gh]

Void linux and radeon 5500tx, I have the glew, glew-devel, glfw-wayland, and glfw-devel packages installed currently

[nigels-com]

GLEW can be built in EGL mode, but I don't know if they're being packaged by distros that way.

[wbehrens-on-gh]

What exactly is egl mode and how can I check if it's being packaged that way here's the void package for glew

[nigels-com]

EGL is a newer alternative to GLX. Seems like with Wayland we get X11 emulation, but not GLX. Worth trying on your setup: https://github.com/nigels-com/glew#linux-egl

LDFLAGS.GL = -lEGL -lGL
CFLAGS.EXTRA += -DGLEW_EGL

[wbehrens-on-gh]

trying with both g++ gl_window.cpp -lglfw -lGLEW -lGL -lGLU -lEGL -DGLEW_EGL -o gl_window and g++ gl_window.cpp $(pkg-config --libs --cflags glfw3 glew egl) -DGLEW_EGL -o gl_window neither work and give the same exit code

[nigels-com]

It's the GLEW library itself that needs to be built in EGL mode.

[wbehrens-on-gh]

Will building with EGL remove x11 support or just adds egl? how does that all work?

[nigels-com]

Yes, it's EGL or GLX currently, but not both at the same time. There is some interest in GLEW being able to support either or both at runtime, but it hasn't been looked at in detail.

[wbehrens-on-gh]

ah, understood. I'll just create an additional package in the void repos for it