How to handle, when tkinter window gets focus

Question

I have this code:

from tkinter import *
w = Tk()
w.protocol('WM_TAKE_FOCUS', print('hello world'))
mainloop()

It prints hello world only once, and then it stops working. No more hello world Basically WM_TAKE_FOCUS does not work.

Answer 1

You can bind a function to the <FocusIn> event. When you bind to the root window the binding is applied to every widget in the root window, so if you only want to do something when the window as a whole gets focus you'll need to compare event.widget to the root window.

For example:

import Tkinter as tk

def handle_focus(event):
    if event.widget == root:
        print("I have gained the focus")

root = tk.Tk()
entry1 = tk.Entry(root)
entry2 = tk.Entry(root)

entry1.pack()
entry2.pack()

root.bind("<FocusIn>", handle_focus)

root.mainloop()

Answer 2

"Note that WM_SAVE_YOURSELF is deprecated, and Tk apps can't implement WM_TAKE_FOCUS or _NET_WM_PING correctly, so WM_DELETE_WINDOW is the only one that should be used". Here's a link! If you need to keep tkinter focus all the time:

w.wm_attributes("-topmost", 1)

does a pretty good job.