CODEWITHSUNDEEP
c++copengl
Thomas Roe
Thomas Roe

Reputation: 23

Where is the OpenGL context stored?

I am fairly new to OpenGL and have been using GLFW combined with GLEW to create and display OpenGL contexts. The following code snippet shows how I create a window and use it for OpenGL.

GLFWwindow* window;

if (!glfwInit())
{
    return -1;
}

window = glfwCreateWindow(1280, 720, "Hello OpenGL", NULL, NULL);

if (!window)
{
    glfwTerminate();
    return -1;
}

glfwMakeContextCurrent(window);

GLenum err = glewInit();

if (err != GLEW_OK)
{
    glfwTerminate();
    return -1;
}

How is glewInit able to fetch the window/context and use it to initialize without myself having to pass any additional arguments to it?

I can only imagine that when we call the glfwMakeContextCurrent function it somehow stores the context somewhere within my process for later use, but no documentation shows this.

Upvotes: 2

Views: 527

Answers (1)

Nicol Bolas
Nicol Bolas

Reputation: 473272

The current OpenGL context is a global (or more to the point, thread_local) "variable" of sorts. All OpenGL functions act on whatever context is active in the current thread at the moment.

This includes the OpenGL calls that GLEW makes.

Upvotes: 3

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