PyOpenGL and GLFW example: adding stuff to VBOs from threads!

demo.py

# imports
from OpenGL.GL import *
from OpenGL.GLU import *
import glfw
import threading

# initialise glfw
if glfw.init() == glfw.FALSE:
    exit()

event = threading.Event()
def shard_context(window, vbo):
    # make a new context
    glfw.window_hint(glfw.VISIBLE, glfw.FALSE)
    window2 = glfw.create_window(300, 300, "Window 2", None, window)
    glfw.make_context_current(window2)
    event.set()
    
    # add the triangle to the VBO.
    glBindBuffer(GL_ARRAY_BUFFER, vbo)
    glBufferSubData(GL_ARRAY_BUFFER, 0, 12*4, (GLfloat * 12)(0.0, 0.5, 0.0, -0.5, -0.5, 0.0, 0.5, -0.5, 0.0))
    glFlush()

# make the main window
window = glfw.create_window(300, 300, "Window 1", None, None)
glfw.make_context_current(window)

# make the vbo
vbo = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, vbo)
glBufferData(GL_ARRAY_BUFFER, 12 * 4, None, GL_STATIC_DRAW)

# start the triangle thread
glfw.make_context_current(None)
thread = threading.Thread(target=shard_context, args=[window, vbo])
thread.start()
event.wait()
glfw.make_context_current(window)

# vbo stuff
glEnableClientState(GL_VERTEX_ARRAY)
glVertexPointer(3, GL_FLOAT, 0, None)

# mainloop
while not glfw.window_should_close(window):
    
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    
    glColor3f(1, 0, 0)
    # draw the vbo
    glDrawArrays (GL_TRIANGLES, 0, 3)

    glfw.swap_buffers(window)
    glfw.poll_events()

# exit
glfw.terminate()
exit()