Cannot close multithreaded Tkinter app on X button

Question

My app has the following structure:

import tkinter as tk
from threading import Thread

class MyWindow(tk.Frame):
    ...  # constructor, methods etc.

def main():
    window = MyWindow()
    Thread(target=window.mainloop).start()
    ...  # repeatedly draw stuff on the window, no event handling, no interaction

main()

The app runs perfectly, but if I press the X (close) button, it closes the window, but does not stop the process, and sometimes even throws a TclError.

What is the right way to write an app like this? How to write it in a thread-safe way or without threads?

Answer 1

Main event loop should in main thread, and the drawing thread should in the second thread.

The right way to write this app is like this:

import tkinter as tk
from threading import Thread

class DrawingThread(Thread):
    def __init__(wnd):
        self.wnd = wnd
        self.is_quit = False

    def run():
        while not self.is_quit:
            ... # drawing sth on window

    def stop():
        # to let this thread quit.
        self.is_quit = True

class MyWindow(tk.Frame):
    ...  # constructor, methods etc.
    self.thread = DrawingThread(self)
    self.thread.start()

    on_close(self, event):
        # stop the drawing thread.
        self.thread.stop()

def main():
    window = MyWindow()
    window.mainloop()

main()