PySimpleGUI and custom usb joystick input

I am trying to make an arcade style user guided story book terminal using PySimpleGUI and a custom made usb joystick providing the input. I have created a PySimpleGUI imageloader with the button prompts. Image viewer:

import io
import os
import PySimpleGUI as sg
from PIL import Image

image = Image.open("/path/to/file.jpg")
image.thumbnail((200, 200))
bio = io.BytesIO()
image.save(bio, format="PNG")

layout = [[sg.Image(key="-IMAGE-")],
          [sg.Button("Green"),
           sg.Button("Blue"),]
          ]
window = sg.Window("Image Viewer", layout, finalize=True)
window["-IMAGE-"].update(data=bio.getvalue())

while True:

    event, values = window.read()
    if event == "Exit" or event == sg.WIN_CLOSED:
        break
    if event == "Green":
        load_image_str = "g"
    if event == "Blue":
        load_image_str = "b"

    file_path = ("/path/to/folder" + load_image_str + ".jpg")

    if os.path.exists(file_path) and file_path.endswith('.jpg'):
        image = Image.open("/path/to/file")
        image.thumbnail((400, 400))
        bio = io.BytesIO()
        image.save(bio, format="PNG")
        window["-IMAGE-"].update(data=bio.getvalue())

window.close()

Joystick input

from evdev import InputDevice, ecodes

#Button codes
greenBtn = 288
blueBtn = 289

device = InputDevice('/dev/input/eventXX')

def main():
    for event in device.read_loop():
        if event.type == ecodes.EV_KEY:
            if event.value == 1:
                if event.code == greenBtn:
                    print("green")
                if event.code == blueBtn:
                    print("blue")


if __name__ == "__main__":
    x =main()

The image viewer and the joystick are working as I expected but I don't know where to even start combining the two. Am I on the right track here or should I be looking at a different way to do this?

If you use a thread for the joystick part, then your GUI can wait on Joystick events and handle them or handle events from the GUI itself.

import PySimpleGUI as sg
import time
import random

# thread for joystick handling
def joystick_thread(window):
    while True:
        time.sleep(1)                # Replace with your read joystick code

        # If got some kind of joystick event
        value = random.randint(200, 250)
        window.write_event_value(('-JOYSTICK-', '-EV KEY-'), value)

# The GUI Portion
def main():
    layout = [  [sg.Text('Joystick Monitor Window')],
                [sg.Text(key='-OUT-')],
                [sg.Button('Does Nothing'), sg.Button('Exit')]  ]

    window = sg.Window('Joystick', layout, finalize=True)
    
    # Startup the joystick thread
    window.start_thread(lambda: joystick_thread(window), ('-JOYSTICK-', '-ENDED-'))

    while True:             # Event Loop
        event, values = window.read()
        print(event, values)
        if event == sg.WIN_CLOSED or event == 'Exit':
            break

        if event[0] == '-JOYSTICK-':
            if event[1] == '-ENDED-':
                break
            if event[1] == '-EV KEY-':
                window['-OUT-'].update(f'Joystick event received {values[event]}')
    window.close()

if __name__ == '__main__':
    main()