5 Best Ways to Disable the Underlying Window When a Popup is Created in Python Tkinter

💡 Problem Formulation: In Python’s Tkinter module, creating auxiliary windows like popups and dialogs is common. However, ensuring that these secondary windows capture user focus and prevent interaction with the main window until dismissed can enhance the usability and flow of an application. This concept is known as “modal” behavior. We aim to showcase five methods to achieve modal-like functionality where the underlying window is disabled when a popup is created, ensuring proper application flow and user experience.

Method 1: Using grab_set()

This method revolves around the grab_set() function, which confines input to the popup window until it is destroyed or releases the grab. It’s a neat trick to prevent the user from clicking on the main application window when the popup is active.

Here’s an example:

import tkinter as tk

def create_popup():
    popup = tk.Toplevel()
    popup.grab_set()
    tk.Label(popup, text="Popup content here").pack()
    tk.Button(popup, text="Close", command=popup.destroy).pack()

root = tk.Tk()
tk.Button(root, text="Open popup", command=create_popup).pack()
root.mainloop()

Output: A main window with a button labeled “Open popup”. Clicking this button opens a popup window with text and a “Close” button. While the popup is open, the main window is disabled.

The code example demonstrates the creation of a simple popup window using the Toplevel widget. The crucial part is the popup.grab_set() call, which effectively disables the main window. Once the popup is closed, input control returns to the main application.

Method 2: The wait_window() Approach

The wait_window() method will make the main application window wait until the specified window is closed. This is another way to achieve modality by freezing the main application until the popup is handled.

Here’s an example:

import tkinter as tk

def create_popup():
    popup = tk.Toplevel()
    tk.Label(popup, text="Please make a choice").pack()
    tk.Button(popup, text="OK", command=popup.destroy).pack()
    root.wait_window(popup)

root = tk.Tk()
tk.Button(root, text="Show popup", command=create_popup).pack()
root.mainloop()

Output: The main application window will wait and be unresponsive until the popup window is dismissed.

This snippet implements the use of root.wait_window(popup), which pauses the code execution on the main window until the popup window is closed. It is a simple and effective solution for many modal dialog needs.

Method 3: Disabling Main Window Widgets Individually

For an alternative approach where you may want to only disable a subset of widgets, you can individually set the state of each widget in the main window to ‘disabled’. This method offers more control over which parts of the main window are affected.

Here’s an example:

import tkinter as tk

def create_popup():
    for widget in root.winfo_children():
        widget.config(state='disabled')
    popup = tk.Toplevel()
    tk.Label(popup, text="Perform action in popup").pack()
    tk.Button(popup, text="Done", command=lambda: enable_widgets(popup)).pack()

def enable_widgets(popup):
    for widget in root.winfo_children():
        widget.config(state='normal')
    popup.destroy()

root = tk.Tk()
tk.Button(root, text="Disable main window", command=create_popup).pack()
root.mainloop()

Output: A main window with its widgets disabled while the popup is open. Upon closing the popup, the widgets are re-enabled.

In this example, the create_popup() function is responsible for disabling all widgets in the main window upon invoking a popup. The enable_widgets() function is triggered when the popup is done, re-enabling the widgets and destroying the popup.

Method 4: Overriding Window Protocol Handlers

By setting a custom command to the ‘WM_DELETE_WINDOW’ window protocol, you can intercept the event when a user tries to close the window, providing custom behavior like forcefully setting focus back to the popup until it’s properly dismissed.

Here’s an example:

import tkinter as tk

def create_popup():
    popup = tk.Toplevel()
    popup.grab_set()
    popup.protocol("WM_DELETE_WINDOW", lambda: focus_popup(popup))

def focus_popup(popup):
    popup.focus_set()
    popup.bell() # to alert the user

root = tk.Tk()
tk.Button(root, text="Open popup", command=create_popup).pack()
root.mainloop()

Output: A popup that doesn’t close when attempting to exit and instead beeps to signal the user to take action within the popup.

This code captures an attempt to close the popup window without proper action. The focus_popup() function is triggered when the user tries to close the window, forcing focus back to the popup and playing an alert sound.

Bonus One-Liner Method 5: Using attributes()

Sometimes you might want a quick one-liner that can effectively disable all interactions with the main window, not just within the Tkinter environment but also from the window manager’s perspective. You can set the disabled attribute of the main window, which universally disables it.

Here’s an example:

import tkinter as tk

def create_popup():
    root.attributes('-disabled', 1)
    popup = tk.Toplevel()
    tk.Label(popup, text="Popup active").pack()
    tk.Button(popup, text="Close", command=lambda: [popup.destroy(), root.attributes('-disabled', 0)]).pack()

root = tk.Tk()
tk.Button(root, text="Open popup", command=create_popup).pack()
root.mainloop()

Output: The main window is completely disabled and will not accept any input until the popup is closed and the attribute is reset.

This code disables the main window using root.attributes('-disabled', 1) when the popup opens. Once the popup closes with the “Close” button, root.attributes('-disabled', 0) is called to re-enable the window.

Summary/Discussion

Method 1: grab_set()
• Strengths: Simple, targeted, and ensures that focus is directed properly. Grabs are automatically released when the popup is destroyed.
• Weaknesses: Does not prevent interaction with windows from other applications.
Method 2: wait_window()
• Strengths: Code execution is halted preventing any interaction with the main window. Very easy to implement.
• Weaknesses: It’s a blocking call, which may not be ideal for all situations.
Method 3: Disable Individual Widgets
• Strengths: Offers granular control over which widgets are disabled. Customizable.
• Weaknesses: Requires more code and managing the state of each widget.
Method 4: Overriding Window Protocol Handlers
• Strengths: Combines control over window interactions with customized alert behavior.
• Weaknesses: It may confuse users if not implemented with clear communication.
Bonus One-Liner Method 5: attributes()
• Strengths: A very quick implementation that uses built-in window manager features.
• Weaknesses: Less control over behavior, and not all window managers may support this attribute.