Turtlebot 3 joystick control

import pyglet
from pyglet.gl import *
import rospy
from geometry_msgs.msg import Twist
import sys

LINEAR_X_STEP = 0.05
ANGULAR_Z_STEP = 0.1

joysticks = pyglet.input.get_joysticks()
assert joysticks, 'No joystick device is connected'
joystick = joysticks[0]
joystick.open()
window = pyglet.window.Window()

linear_x = 0.0
angular_z = 0.0
rospy.init_node("controller", anonymous=True)
publisher = rospy.Publisher("cmd_vel", Twist, queue_size = 100)
message = Twist()
message.linear.x = message.linear.y = message.linear.z = 0
message.angular.x = message.angular.y = message.angular.z = 0

def axes(x, y, z, angle):
    glClear(GL_COLOR_BUFFER_BIT)
    glColor3f(1, 0, 0)
    glLoadIdentity()
    glTranslatef(x, y, 0)
    glScalef(1 + z, 1 + z, 1 + z)
    glRotatef(-angle, 0, 0, 1)
    glBegin(GL_TRIANGLES)
    glVertex2f(-10, 0)
    glVertex2f(0, 13)
    glVertex2f(10, 0)
    glEnd()

def buttons(x, y):
    global linear_x, angular_z
    glLoadIdentity()
    x = 10
    y = 10
    glPointSize(5)
    glBegin(GL_POINTS)
    buttons = joystick.buttons

    if buttons[2]:
        linear_x = 0.0
        angular_z = 0.0

    if buttons  [3]:
        linear_x = 0.0
        angular_z = 0.0
        sys.exit()

    for button in buttons:
        if button:
            glVertex2f(x, y)
        x += 20
    glEnd()

def control_robot(x, y):
    global linear_x, angular_z
    if y == 1.0:
        linear_x += LINEAR_X_STEP
    elif y == -1.0:
        linear_x -= LINEAR_X_STEP
    elif x == -1.0:
        angular_z += ANGULAR_Z_STEP
    elif x == 1.0:
        angular_z -= ANGULAR_Z_STEP

def hat():
    glColor3f(0, 0, 1)
    x = window.width / 2
    y = window.height / 2
    glBegin(GL_POINTS)

    control_robot(joystick.hat_x, joystick.hat_y)

    glVertex2f(x + joystick.hat_x * 50, y + joystick.hat_y * 50)
    glEnd()

@window.event
def on_draw():
    x = (0.8*joystick.x + 1) * window.width / 2
    y = (-0.8*joystick.y + 1) * window.height / 2
    z = joystick.z
    angle = joystick.rz * 180

    axes(x, y, z, angle)

    buttons(x, y)

    hat()

    message.linear.x = linear_x
    message.angular.z = angular_z
    print("Linear: ", linear_x, "Angular: ", angular_z)
    publisher.publish(message)

pyglet.clock.schedule(lambda dt: None)
pyglet.app.run()