#define GL_GLEXT_PROTOTYPES
#define GLX_GLXEXT_PROTOTYPES

#include <X11/Xlib.h>
#include <GL/gl.h>
#include <GL/glx.h>

// These are obsolete in most distributions, hence provided explicitly.
#include "GL/glxext.h"
#include "GL/glext.h"

Display *d_dpy;
Window d_win;
GLXContext d_ctx;

// Set to NULL for getting it from the environment variable
const char *display = ":0"; 
int width = 2560;
int height = 1600;

if (!(d_dpy = XOpenDisplay(display))) {
    throw std::string("Couldn't open X11 display\n");
}

int attr[] = {
    GLX_RGBA,
    GLX_RED_SIZE, 1,
    GLX_GREEN_SIZE, 1,
    GLX_BLUE_SIZE, 1,
    GLX_DOUBLEBUFFER,
    GLX_DEPTH_SIZE, 1,
    None
};

int scrnum = DefaultScreen(d_dpy);
Window root = RootWindow(d_dpy, scrnum);

// We need this for OpenGL3
int elemc;
GLXFBConfig *fbcfg = glXChooseFBConfig(d_dpy, scrnum, NULL, &elemc);
if (!fbcfg) 
    throw std::string("Couldn't get FB configs\n");
else
    printf("Got %d FB configs\n", elemc);

XVisualInfo *visinfo = glXChooseVisual(d_dpy, scrnum, attr);

if (!visinfo)
    throw std::string("Couldn't get a visual\n");

// Window parameters
XSetWindowAttributes winattr;
winattr.background_pixel = 0;
winattr.border_pixel = 0;
winattr.colormap = XCreateColormap(d_dpy, root, visinfo->visual, AllocNone);
winattr.event_mask = StructureNotifyMask | ExposureMask | KeyPressMask;
unsigned long mask = CWBackPixel | CWBorderPixel | CWColormap | CWEventMask;

printf("Window depth %d, w %d h %d\n", visinfo->depth, width, height);
d_win = XCreateWindow(d_dpy, root, 0, 0, width, height, 0, 
        visinfo->depth, InputOutput, visinfo->visual, mask, &winattr);

// OpenGL 3.2
int gl3attr[] = {
    GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
    GLX_CONTEXT_MINOR_VERSION_ARB, 2,
    GLX_CONTEXT_FLAGS_ARB, GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
    None
};

d_ctx = glXCreateContextAttribsARB(d_dpy, fbcfg[0], NULL, true, gl3attr);

XFree(visinfo);

XMapWindow(d_dpy, d_win);
glXMakeCurrent(d_dpy, d_win, d_ctx);

printf("OpenGL:\n\tvendor %s\n\trenderer %s\n\tversion %s\n\tshader language %s\n\n",
        glGetString(GL_VENDOR), glGetString(GL_RENDERER), glGetString(GL_VERSION),
        glGetString(GL_SHADING_LANGUAGE_VERSION));

int extCount;
glGetIntegerv(GL_NUM_EXTENSIONS, &extCount);
for (int i = 0; i < extCount; ++i)
    printf("Extension %d/%d: %s\n", i+1, extCount, glGetStringi(GL_EXTENSIONS, i));

glViewport(0, 0, width, height);