[GUI plugin] Palette Switcher

[dunhill]

Palette Switcher is a Calibre interface plugin that lets you manage and apply custom color palettes to the Calibre GUI. It provides a modular and reproducible way to change the look and feel of Calibre

Features
Adds a toolbar icon to access the palette manager.
Automatically detects .calibre-palette files.
Lets you select and apply a palette from a popup window.
Supports importing and exporting palettes for easy sharing.
The plugin's title bar indicates which palette is in use.

File Structure
Files must use the .calibre-palette extension.

Compatibility
Requires Calibre 6.25 or later.
Should work on Windows, macOS, and Linux.
Tested primarily on Linux — feedback from macOS and Windows users is welcome.

License
This plugin is released under the GNU GPL v3 license.

Credits
Special thanks to Comfy.n for their help in making the plugin work.

Release notes:

Spoiler:

05/03/26 v-1.1.1 Stability & Resource Management Update
This version introduces critical safeguards to prevent crashes and optimizes the theme preview mechanism.
RCC Lock Protection: Added a robust error handling system (OSError/PermissionError) for UI refreshes. This prevents Calibre from crashing if the icons-any.rcc file is momentarily locked by the OS during a palette change.
Icon Theme Notice: If you are using a custom Calibre icon set, please note that while colors update instantly, a restart of Calibre is required for the icon set to fully refresh and match the new visual mode (e.g., switching between Light and Dark icons).
Smooth Preview: The 300ms preview delay ensures stable file I/O operations while scrolling through the palette list.

23/02/26 v1.0.96 Minor error corrections

22/02/26
v1.0.92-93-94: System Intelligence and Full Accessibility
This update is a significant milestone in the plugin's development, incorporating suggestions from our community to achieve a perfect balance between new features and ease of use.
Main New Features:
Intelligent Mode Detection (System): The plugin now includes a luminance algorithm that automatically detects whether your operating system is in light or dark mode. The mode button now allows you to cycle through: Light / Dark / Auto (System)
Hands-on Keyboard Accessibility: We've optimized the workflow for keyboard users:
Immediate Focus: When you open the plugin, the palette list automatically takes focus. Use the arrow keys (↑/↓) for instant previews.
Logical Tab Order: Pressing Tab simplifies the cursor's movement: List -> Apply -> Cancel -> Exit. Fewer keystrokes, more speed.
Execution with Enter: Confirming and applying your changes is now as simple as pressing Enter.

21/02/26
Version 1.0.91
Navigation restored: The plugin now opens with the list in focus. You can navigate the palettes with ↑/↓, quickly jump to the main buttons with Tab, and confirm with Enter. I've optimized the tab order to be as short and logical as possible.
Bug fixed: The UnboundLocalError when exporting is now a thing of the past.

v1.0.9 - Secure Editing and Dynamic Preview
New workflow: Apply, Cancel, and Exit buttons have been added. Changes are now only permanent if confirmed by the user.
Live preview: Themes are temporarily applied when selected from the list for easier selection.
Automatic backup: The plugin remembers Calibre's initial state and allows changes to be reverted if the user is not satisfied.
Live export: Ability to generate .calibre-palette files from the user's currently active color configuration.
UX improvements: Tooltips have been added to all buttons and mode indicators (Light/Dark).

14/02/26
Version 1.0.7 Remembers the plugin window size.
Added exit button.

Version 1.0.6 Displays the palette applied in the plugin title

09/02/26 Version 1.0.5: Removed the confirmation dialogs for palette deletion.

8/02/26 Version 1.0.4: Added a button to delete the selected color palette

Version 1.0.3:
A button has been added to reset Calibre's default color palette settings. This was requested by JSWolf.

Version 1.0.2:
Instantly switch (with a simple selection) between palette files, supports importing from zip files, and skips duplicate palettes.
Comfy.n Update

Version 1.0.0
Thanks to the help of Comfy.n, this plugin was released.
Translation support added
Internal fixes

[dunhill]

Color palette files collected by Comfy.n from the thread
https://www.mobileread.com/forums/sh...d.php?t=359611

A compact archive containing only the .palette files.
(The larger archive contains other files that their authors chose to share in their original posts, such as readme.txt files and screenshots.)

[Comfy.n]

That's a good starting point, I think.

I prefer the version with automatic palette refresh upon selection.

I managed to make a big archive containing all palette files posted in the Color Palettes thread, imported them with a single click, and now I'm enjoying several themes I hadn't tried before.

Congratulations on your first plugin and thanks for the credits.

[dunhill]

Originally Posted by Comfy.n

That's a good starting point, I think.

I prefer the version with automatic palette refresh upon selection.

I managed to make a big archive containing all palette files posted in the Color Palettes thread, imported them with a single click, and now I'm enjoying several themes I hadn't tried before.

Congratulations on your first plugin and thanks for the credits.

That was the idea behind the add-on; I'm reviewing your file.
Thanks again. Imagine, it's midnight and I'm working flat out here.

[Comfy.n]

I'm trying to figure how some themes are able to style the border outline of the *native* calibre scrollbar handle. I didn't know this is possible.

[dunhill]

Originally Posted by Comfy.n

I'm trying to figure how some themes are able to style the border outline of the *native* calibre scrollbar handle. I didn't know this is possible.

It could be specific to the palette file that QSS is handling, or something

QScrollBar:vertical { border: 1px solid #444; background: #2b2b2b; width: 12px; margin: 0px 0px 0px 0px; } QScrollBar::handle:vertical { background: #888; min-height: 20px; border: 1px solid #555; }

[dunhill]

Here's an improved version that can instantly switch (with just a select) between palette files, supports importing from zip files, and skips duplicate palettes.
Comfy.n Update

[BetterRed]

both

I couldn't be bothered with palettes until now. I've long wanted to use different palettes for each of the calibre installs I dodge between.

What I'd like now is a palette browser - wading through 5 pages of posts in the Colour palettes thread and fishing around elsewhere is tedious. For me it doesn't have to be a calibre plugin, it fact I'd rather it wasn't, maybe a github page of some sort… or DeviantArt maybe.

Anyway - thanks again.

BR

[Terisa de morgan]

I've used it now and it works prefectly. Just a doubt... how do you go back to the default dark or light theme?

--- Forget about it, I found it. Thank you.

[BetterRed]

Originally Posted by Terisa de morgan

I've used it now and it works prefectly. Just a doubt... how do you go back to the default dark or light theme?

--- Forget about it, I found it. Thank you.

Care to share.

BR

[Terisa de morgan]

Preferences -> Look & Feel -> Main Interface -> Adjust Colors -> Restore defaults.

[JSWolf]

Originally Posted by Comfy.n

That's a good starting point, I think.

I prefer the version with automatic palette refresh upon selection.

I managed to make a big archive containing all palette files posted in the Color Palettes thread, imported them with a single click, and now I'm enjoying several themes I hadn't tried before.

Congratulations on your first plugin and thanks for the credits.

Would you mind posting this archive please? Thanks.

[JSWolf]

@dunhill, would you mind adding a return to default button? I know you can do it in calibre's preferences, I see many people no knowing you can do this and/or how.

[Comfy.n]

Originally Posted by JSWolf

Would you mind posting this archive please? Thanks.

Sure, it's attached.

[Comfy.n]

And this is a compact archive that contains only the .palette files.

(the larger archive contains other files their authors chose to share on their original posts, such as readme.txt files and screenshots)