Applications can optionally generate graphics, which are displayed by the core client in either its application (window) or screensaver (full-screen) form.
void init_opengl(APP_IN_GRAPHICS); void draw_opengl(); void gl_done();The application must supply a function
draw_gl();The draw_gl function is called when graphics need to be drawn to the screen. At the completion of the draw_gl function, gl_done must be called.