gistfile1.nim

var
  vertArrayObject: GLuint
  vertBufferObject: GLuint

proc init =
  var verts = [
    0f32, 0f32, 0f32,
    4f32, 0f32, 0f32,
    0f32, 4f32, 0f32,
    
    0f32, 4f32, 0f32,
    4f32, 0f32, 0f32,
    4f32, 4f32, 0f32 ]
  
  glGenVertexArrays(1, addr vertArrayObject)
  glBindVertexArray(vertArrayObject)
  
  glGenBuffers(1, addr vertBufferObject)
  glBindBuffer(GL_ArrayBuffer, vertBufferObject)
  glBufferData(GL_ArrayBuffer, verts.sizeof.GL_SizeIPtr, addr verts, GL_StaticDraw)
  glVertexAttribPointer(0, 3, CGL_Float, false, 0, nil)
  glEnableVertexAttribArray(0)
  
  glBindVertexArray(0)

proc render =
  # clear..
  glClearColor(0.2, 0.5, 0.5, 1)
  glClear(GL_ColorBufferBit)
  
  # bind to your VAO handle
  glBindVertexArray(vertArrayObject)
  
  # draw
  glDrawArrays(GL_Triangles, 0, 6) # draw 6 verts
  
  # unbind it
  glBindVertexArray(0)
  
  # present...
  SDL.glSwapWindow(...)