Question

Here’s my initialization code:

const int WIN_HEIGHT = 640;
const int WIN_WIDTH = 640;
void main(int argc, char **argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);

    /* lines in question */
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_NORMALIZE);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glShadeModel(GL_SMOOTH);

    glutInitWindowSize(WIN_WIDTH, WIN_HEIGHT);
    glutCreateWindow("OpenGL");
    glutDisplayFunc(Draw);
    glutKeyboardFunc(HandleInput);
    Initialize();

    glutMainLoop();
}

So, most of that code is pretty boilerplate for a basic 3D program. The problem is, if I put all the glEnable() lines before glutCreateWindow() they are reset. It’s an easy enough fix to move them after creating the window (I moved them to my own Initialize() function), but why would glutCreateWindow() disable these?

Answer 1

I would say it’s because a context has not yet been created before your call to glutCreateWindow(). You are then able to set them after one is created, as can be interpreted from the following text:

In order for any OpenGL commands to work, a context must be current; all OpenGL commands affect the state of whichever context is current.

Since there was no context (or an old, invalid one), your calls to glInit() don’t affect the current window’s context.