OpenGL and X

import x
import xlib
import glx
import opengl
import glu

var attr: array[0..4, int32] = [ GLX_RGBA, GLX_DEPTH_SIZE, 24, GLX_DOUBLEBUFFER, None ]
var swa: TXSetWindowAttributes
var xev: TXEvent
var gwa: TXWindowAttributes

proc drawQuad() =
  glClearColor(1.0, 1.0, 1.0, 1.0)
  glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT)

  glMatrixMode(GL_PROJECTION)
  glLoadIdentity()
  glOrtho(-1.0, 1.0, -1.0, 1.0, 1.0, 20.0)

  glMatrixMode(GL_MODELVIEW)
  glLoadIdentity()
  gluLookAt(0.0, 0.0, 10.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0)

  glBegin(GL_QUADS)
  block draw:
    glColor3f(1.0, 0.0, 0.0)
    glVertex3f(-0.75, -0.75, 0.0)
    glColor3f(0.0, 1.0, 0.0)
    glVertex3f(0.75, -0.75, 0.0)
    glColor3f(0.0, 0.0, 1.0)
    glVertex3f(0.75, 0.75, 0.0)
    glColor3f(1.0, 1.0, 0.0)
    glVertex3f(-0.75, 0.75, 0.0)
  glEnd()

let dpy = XOpenDisplay(nil)

if dpy == nil:
  quit(1)

let root = DefaultRootWindow(dpy)
let vi = glXChooseVisual(dpy, 0, addr attr[0])

if vi == nil:
  quit(2)

let cmap = XCreateColormap(dpy, root, vi.visual, AllocNone)

swa.colormap = cmap
swa.event_mask = ExposureMask or KeyPressMask

let win = XCreateWindow(dpy, root, 0, 0, 800, 600, 0, vi.depth, InputOutput, vi.visual, CWColorMap or CWEventMask, addr swa)

discard XMapWindow(dpy, win)
discard XStoreName(dpy, win, "Test 1")

let glc = glXCreateContext(dpy, vi, nil, true)
discard glXMakeCurrent(dpy, win, glc)

glEnable(GL_DEPTH_TEST)

while true:
  discard XNextEvent(dpy, addr xev)
  if xev.theType == Expose:
    discard XGetWindowAttributes(dpy, win, addr gwa)
    glViewport(0, 0, gwa.width, gwa.height)
    drawQuad()
    glXSwapBuffers(dpy, win)
  elif xev.theType == KeyPress:
    discard glXMakeCurrent(dpy, None, nil)
    glXDestroyContext(dpy, glc)
    discard XDestroyWindow(dpy, win)
    discard XCloseDisplay(dpy)
    quit(0)