[Question] How to update modeline when switching themes?

[SophieBosio]

Hi,

I have an issue where the colour of the modeline does not update when switching themes.

Here is a screenshot of the theme I use on start-up, the doom-nord theme.

And here is a screenshot after switching to ef-maris-light, where the modeline retains the doom-nord colours.

This problem is persistent with all themes. For instance, if I use ef-maris-light on start-up and switch to doom-nord, then doom-nord will have a ef-maris-light-coloured modeline.

I had some issues with lingering borders when switching themes, so in my configuration, I have this code snippet that advices load-theme to always disable the current theme when switching themes. This has resolved the issue for borders and other UI elements, such as source code blocks in Org-documents, but does not seem to affect nano-modeline. Removing this snippet also does not resolve the nano-modeline issue.

(defadvice load-theme
  (before disable-before-load (theme &optional no-confirm no-enable) activate)
  (mapc 'disable-theme custom-enabled-themes))

I would really appreciate any help! My full config is also available https://github.com/SophieBosio/.emacs.d.

[rougier]

I think the problem is quite generic and the solution you've found seems to be the "official" one:

• https://stackoverflow.com/questions/22866733/emacs-disable-theme-after-loading-a-different-one-themes-conflict
• https://www.reddit.com/r/emacs/comments/mm2lwk/changing_themes_messes_up_some_elements/

The reason might be that some theme do not modify everything (nor does nano-modeline) such that if a theme modify something that is not overwritten by the new theme, it will remains as it is (i.e. from previous theme)

[SophieBosio]

Thank you for the response! Seems like it is indeed a question of what things the new theme modifies when switching.

I also noticed that the nano themes do in fact change the colour of the modeline, so when I want to switch to a theme that doesn't update the modeline colour, so a hacky solution is to always change to a nano theme before changing to a different theme. E.g., to change from doom-nord to ef-maris-light, I can first change to nano-light and then to ef-maris-light. Then the modeline colour is fitting even if it's not the exact colour of the theme I'm using.

[rougier]

Did you try (disable-theme 'nano-theme)? (never tested though)

[SophieBosio]

That's interesting! When I switch from doom-nord to nano-light everything including the modeline updates. Then, if I run M-x disable-theme RET nano-theme RET, the theme switches to the Emacs default but the doom-nord modeline colours come back. So somehow, it seems that the theme used at startup is the modeline's "fallback" colours.

Putting (disable-theme 'nano-theme) in the load-theme advice didn't seem to have any effect, unfortunately.

[rougier]

Hum, maybe I set some settings without using the custom machinery, that may explain things. I need to have a closer look at the sources.

[SophieBosio]

Thank you for looking into this, I appreciate it!

[rougier]

Ok, now I remember: https://github.com/rougier/nano-modeline/issues/54 This means I need to remove the indirect mechanism in favor of regular faces. I'll re-open the issue since I'm not too sure when I can make the change. Don't hesitate to ping me here to enquiry about any advance.

[PavelNovichkov]

A workaround that works for me is to explicitly reset nano-modeline-active face to its default value after switching themes:

(defun my/nano-modeline-update (&rest _)
    "Update nano-modeline active face."
    (custom-set-faces
     `(nano-modeline-active
       ((t (:foreground ,(face-foreground 'default)
            :background ,(face-background 'header-line nil t)
            :box (:line-width 1 :color ,(face-background 'default))))))))
(add-hook 'enable-theme-functions #'my/nano-modeline-update)