Catch macos ⌘Q in python tkinter application - python-3.x

Question

eWithin a tkinter application I am catching several events to gracefully shutdown some threads within the application, before the main thread terminates.
This is all working swiftly as long as I use a bound key combination or the
window control, the cross in the red circle.
On macos the application automatically gets a 'python' menu with a close function bound to key combination ⌘Q. This event is not handled properly. It seems to kill the main thread but other threads are not closed properly.
Following bindings are used to catch all closing events:
self.root.bind('<Control-x>', self.exitapp)
self.root.protocol("WM_DELETE_WINDOW", self.exitapp)
atexit.register(self.catch_atexit)
Recently found that the left and right ⌘ keys are repesented as Meta_L and Meta_R but cannot be combined with a second key, i.e. '<Meta_L-q>'.
Can anyone explain howto catch ⌘Q?
Please find code example below:
#!/usr/bin/env python3
import sys
from tkinter import *
from tkinter import ttk
import threading
import time
import atexit
class subthread():
def __init__(self):
self.thr = None
self.command = ''
self.proof = ""
def start(self):
if not self.thr or not self.thr.is_alive():
self.command = 'run'
self.thr = threading.Thread(target=self.loop)
self.thr.start()
else:
print('thread already running')
def stop(self):
self.command = 'stop'
if self.thr and self.thr.is_alive():
print('stopping thread')
else:
print('thread not running')
def running(self):
return True if self.thr and self.thr.is_alive() else False
def get_proof(self):
return self.proof
def loop(self):
while self.command == 'run':
time.sleep(0.5)
print('+', end='')
self.proof += '+'
if len(self.proof) > 30:
self.proof = ""
def __del__(self):
print('del instance subthread')
self.command = 'stop'
if self.thr and self.thr.is_alive():
self.thr.join(2)
class app():
def __init__(self, rootframe):
self.root = rootframe
self.gui = ttk.Frame(self.root)
self.gui.pack(fill=BOTH)
row = 0
self.checkvar = IntVar()
self.checkvar.trace('w', self.threadchange)
ttk.Label(self.gui, text="Use checkbox to start and stop thread").grid(row=row, column=0, columnspan=2)
ttk.Checkbutton(self.gui, text='thread', variable=self.checkvar).grid(row=1, column=0)
self.threadstatus = StringVar()
self.threadstatus.set('not running')
row += 1
ttk.Label(self.gui, textvariable=self.threadstatus).grid(row=row, column=1)
row += 1
self.alivestring = StringVar()
ttk.Entry(self.gui, textvariable=self.alivestring).grid(row=row, column=0, padx=10, sticky="ew",
columnspan=3)
row += 1
ttk.Separator(self.gui, orient="horizontal").grid(row=row, column=0, padx=10, sticky="ew",
columnspan=3)
row += 1
ttk.Label(self.gui, text="- Available options to close application: [ctrl]-x,"
" window-control-red, [CMD]-q").grid(row=row, column=0, padx=10, columnspan=3)
row += 1
ttk.Label(self.gui, text="1. Try all three without thread running").grid(row=row, column=0,
columnspan=3, sticky='w')
row += 1
ttk.Label(self.gui, text="2. Retry all three after first starting the thread").grid(row=row, column=0,
columnspan=3, sticky='w')
row += 1
ttk.Label(self.gui, text="3. Experience that only [CMD]-q fails").grid(row=row, column=0,
columnspan=3, sticky='w')
self.subt = subthread()
self.root.bind('<Control-x>', self.exitapp1)
self.root.protocol("WM_DELETE_WINDOW", self.exitapp2)
atexit.register(self.catch_atexit)
self.root.after(500, self.updategui)
def threadchange(self, a, b, c):
""" checkbox change handler """
try:
if self.checkvar.get() == 1:
self.subt.start()
else:
self.subt.stop()
except Exception as ex:
print('failed to control subt', str(ex))
def updategui(self):
""" retriggering timer handler to update status label gui """
try:
if self.subt.running():
self.threadstatus.set("thread is running")
else:
self.threadstatus.set("thread not running")
self.alivestring.set(self.subt.get_proof())
except:
pass
else:
self.root.after(500, self.updategui)
def __del__(self):
print('app del called')
def exitapp1(self, a):
print('exitapp1 called')
self.subt.stop()
sys.exit(0)
def exitapp2(self):
print('exitapp2 called')
self.subt.stop()
sys.exit(0)
def catch_atexit(self):
print('exitapp called')
self.subt.stop()
self.subt = None
sys.exit(0)
if __name__ == '__main__':
root = Tk()
dut = app(rootframe=root)
root.mainloop()
print('main exiting')
sys.exit(0)

Answer 1

You can catch ⌘Q with <Command-q>:
...
def action(event):
print("bind!")
root.bind_all("<Command-q>", action)
...
This worked for me on macOS HightSierra

Answer 2

#EddyHoogevorst Yes, it does not work on Big Sur.
The code that works is:
root.createcommand("::tk::mac::Quit", action).
NB: need to change function signature for action as event is not passed as an argument in this context.