如何在不创建窗口的情况下检查OpenGL和GLSL版本？

Question

I tried with following methods - 1. using glew 2. using glut

both almost similar ways as follows -

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

 int main(int agrc, char **argv)
 {
    //do windowing related stuff here

    if ( !glfwInit())
    {
            printf("Error: Failed to initialize GLFW\n");
            return -1;
    }

    GLFWwindow* window = glfwCreateWindow(800, 600, "Triangle", NULL, NULL);
    if (window == NULL)
    {
            printf("Failed to create GLFW window\n");
            glfwTerminate();
            return -1;
    }
    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE;
    if (glewInit() != GLEW_OK)
    {
            printf("Error: Failed to initialize GLEW\n");
            return -1;
    }

    printf("GL version: %s\n", glGetString(GL_VERSION));
    printf("GL shading language version: %s\n", 
    glGetString(GL_SHADING_LANGUAGE_VERSION));
}

Question - Is it possible to check GL and GLSL Version with creating native window?

As per my understanding it is necessary to create GL context which is usually done by creating a window, Please tell me alternative without creating window.

Answer 1

According to the OpenGL Wiki FAQ (emphasis mine).

You must create a GL context in order for your GL function calls to make sense. You can't just write a minimal program such as this:

int main(int argc, char **argv)
{
    char *GL_version=(char *)glGetString(GL_VERSION);
    char *GL_vendor=(char *)glGetString(GL_VENDOR);
    char *GL_renderer=(char *)glGetString(GL_RENDERER);
    return 0;
}

In the above, the programmer simply wants to get information about this system (without rendering anything) but it simply won't work because no communication has been established with the GL driver. The GL driver also needs to allocate resources with respect to the window such as a backbuffer. Based on the pixelformat you have chosen, there can be a color buffer with some format such as GL_BGRA8. There may or may not be a depth buffer. The depth might contain 24 bits. There might be a 8 bit stencil. There might be an accumulation buffer. Perhaps the pixelformat you have chosen can do multisampling. Up until now, no one has introduced a windowless context.

You must create a window. You must select a pixelformat. You must create a GL context. You must make the GL context current (wglMakeCurrent for Windows and glXMakeCurrent for *nix).

That said, if you're just looking to avoid a temporary window popping up, create a non-visible window, so the end-user doesn't have any idea that you're creating the window. In GLFW, it appears you can do this by setting the window hint GLFW_VISIBLE to false with glfwWindowHint before creating the window. All other windowing systems I've worked with have a similar concept of setting the visibility of a window.