Solving the Tkinter/Ttkbootstrap Font Size Issue After Theme Change

Описание: Discover how to maintain consistent font sizes in your Tkinter/Ttkbootstrap applications, even when changing themes. Learn to properly configure your application's default font settings for a seamless user experience.
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This video is based on the question https://stackoverflow.com/q/75422034/ asked by the user 'blaufer' ( https://stackoverflow.com/u/3709645/ ) and on the answer https://stackoverflow.com/a/75422724/ provided by the user 'Bryan Oakley' ( https://stackoverflow.com/u/7432/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Managing Font Size in Tkinter/Ttkbootstrap After a Theme Change

When building an application using Tkinter and Ttkbootstrap, you may encounter an issue where changing themes in your application unexpectedly alters the font size to an undesirable default. If you've faced the inconvenience of your application’s font size resetting back to the default value whenever you switch themes, you’re not alone. In this guide, we'll dive into understanding the problem and provide a solution to keep your font sizes consistent regardless of theme changes.

Understanding the Problem

When users switch themes in your Tkinter application using a combobox, you might notice the following behaviors:

The font size resets to a default value when switching to any theme other than the one originally set.

Upon switching back to the original theme, the font size returns to the previously set value, but only for that theme.

This unexpected behavior happens because the font settings make use of a custom font tied to the theme, rather than modifying the actual default font configuration used across all styles.

Solution: Setting a Consistent Default Font

To ensure that the font size remains the same across different themes while using Tkinter and Ttkbootstrap, you need to change how you define your font. Instead of applying a custom font to the style that may revert when themes change, you should modify the actual default font. This way, any style that utilizes the default Tk font will respect your specified settings.

Steps to Implement

Here is a clear plan to implement a solution:

Import the Required Module: Make sure to import nametofont from tkinter.font at the beginning of your code.

[[See Video to Reveal this Text or Code Snippet]]

Access and Modify the Default Font: Use nametofont to fetch the existing default font and adjust its size using the configure method.

Here's how you can modify the existing code:

[[See Video to Reveal this Text or Code Snippet]]

Why This Works

By modifying the default font using the nametofont method:

You ensure that any widget using TkDefaultFont will reflect the updated size universally, regardless of the theme applied.

You eliminate the need to create a custom font for each specific theme switch, simplifying the overall code structure.

Conclusion

By following the steps outlined above, you can maintain a consistent font size across theme changes in your Tkinter/Ttkbootstrap application. This not only enhances the user experience but also streamlines your code, eliminating the pitfalls associated with isolated font configurations.

If you have further issues or questions regarding Tkinter theming and font management, feel free to reach out or leave a comment below. Happy coding!