How to handle a WM_ENDSESSION in tkinter?

In Tkinter, handling the WM_ENDSESSION Windows message, which is sent to a window when the system is shutting down or restarting, can be a bit challenging since Tkinter's main event loop (mainloop()) does not provide a direct mechanism to catch this specific message. However, you can use a workaround to handle it. Here's an example:

pythonCopy code
import tkinter as tk

import tkinter.messagebox as messagebox

import ctypes



def wndProc(hwnd, msg, wParam, lParam):

    if msg == WM_ENDSESSION:

        # Handle WM_ENDSESSION message

        messagebox.showinfo("Shutdown", "System is shutting down")

        root.destroy()  # Close the Tkinter window

        return True

    return False



# Register the custom window procedure

WM_ENDSESSION = 0x0016

WNDPROC = ctypes.WINFUNCTYPE(ctypes.c_long, ctypes.c_wchar_p, ctypes.c_uint, ctypes.c_long, ctypes.c_long)

windll = ctypes.windll.user32

oldWndProc = windll.SetWindowLongPtrW(root.winfo_id(), -4, WNDPROC(wndProc))



# Create a Tkinter window

root = tk.Tk()

root.title("WM_ENDSESSION Handler")



# Run the Tkinter main event loop

root.mainloop()



# Restore the original window procedure

windll.SetWindowLongPtrW(root.winfo_id(), -4, oldWndProc)

In this example, we register a custom window procedure using the SetWindowLongPtrW function from the user32 library. The custom window procedure (wndProc) checks for the WM_ENDSESSION message and handles it by displaying a message box and closing the Tkinter window.

Please note that this example is specific to Windows operating systems, as the WM_ENDSESSION message is a Windows-specific message. It uses the ctypes module to interact with Windows API functions.