GNU bug report logs - #23403
25.1.50; cua-mode does not interact with cursor-face and themes well

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Message #11 received at 23403 <at> debbugs.gnu.org (full text, mbox):

From: Mauro Aranda <maurooaranda <at> gmail.com>
To: 23403 <at> debbugs.gnu.org
Cc: "Jeremy T. Braun" <spamprevent <at> squidevil.net>
Subject: Re: bug#23403: 25.1.50; cua-mode does not interact with cursor-face
 and themes well
Date: Mon, 17 Mar 2025 07:10:28 -0300

[Message part 1 (text/plain, inline)]

Mauro Aranda <maurooaranda <at> gmail.com> writes:

> "Jeremy T. Braun" <spamprevent <at> squidevil.net> writes:
>
>> I've had issues where themes couldn't change cursor colors.  I finally
>> figured out the culprit, cua-mode.  Details on what I noticed and how I
>> found it follow.
>>
>>
>>
>> I believe the "correct" way for themes to interact with the cursor color
>> is to modify the :background attribute of the face named cursor.  See:
>>
> 
https://www.gnu.org/software/emacs/manual/html_node/emacs/Cursor-Display.html
>>
>> cua-mode defines a variable cua-normal-cursor-color.  By default this is
>> set to one of initial-cursor-color, cursor-color from initial-frame-alis
>> or default-frame-alist, the frame-parameter 'cursor-color, or "red" if
>> those are all not true.
>>
>> When cua-enable-cursor-indications is enabled, cua--update-indications
>> is run as a part of cua--post-command-handler, which is added to
>> post-command-hook.
>>
>> When run, cua-enable-cursor-indications typically calls set-cursor-color
>> to one of the cua-*-cursor-color variables.
>>
>> The result?  Themes can change the cursor-color (via the face or via
>> set-cursor-color, but after they are loaded/run, the post-command-hook
>> eventually runs cua--update-indications, which overwrites the theme's
>> new "normal" cursor color with whatever was previously stored in
>> cua-normal-cursor-color (for "normal" buffers, anyway).
>>
>> I first noticed this because I run emacs in --daemon mode a lot.  When
>> emacs is in --daemon mode, I think that .emacs/init.el is run in the
>> frame/context of the terminal or background emacs process. When my
>> init.el is run, (frame-parameter nil 'cursor-color) returns "white",
>> which cua-normal-cursor-color is set to.  When I switch between the
>> background-mode = dark/light color themes linked below, the cursor
>> always stays white, and it's illegible in the "light" theme.
>> https://github.com/sellout/emacs-color-theme-solarized
>>
>> When I launch emacs without --daemon, my init.el loads the theme first,
>> which sets frame-parameter.cursor-color to #839496, which initializes
>> cua-normal-cursor-color, which is legible in both dark and light modes.
>
> IIUC, the issue here can be reproduced in a couple of ways. Here's one:
> emacs -Q
> M-x cua-mode
> M-x customize-set-variable RET cua-enable-cursor-indications RET y
> M-x load-theme RET deeper-blue
>
> Notice that the cursor is black.  Compare with:
> emacs -Q
> M-x load-theme RET deeper-blue
> M-x cua-mode
> M-x customize-set-variable RET cua-enable-cursor-indications RET y
>
> Now the cursor is green.  If you want, load any other theme, and see
> that the cursor color doesn't change: it stays green.
>
>> I'm not sure how "best" to fix this.  Options I see:
>> * Change documentation on custom themes, requiring that in addition to
>>   modifying the cursor face, they should also modify cua-*-cursor-color.
>
> Themes have pretty much no choice, since it seems to me that for a good
> user experience, they need to make sure all cua-*-cursor-color options
> interact well with their settings.
>
>> * Change cua-mode to be aware that themes may modify the cursor face,
>>   and either update cua-normal-cursor-face to reflect the cursor face's
>>   :background attribute, or maybe have cua--update-indications use
>>   something like:
>>     (or cua-normal-cursor-face (grab the :background attribute of
>>     cursor-face))
>>   And then the user can set/customize cua-normal-cursor-face to nil to
>>   allow the theme to control it.
>
> This idea seems like an improvement.  Allow nil for this option, so that
> it CUA understands it as "don't mess with the cursor color".
>
>
> Opinions?

Here's a patch.  Question is, do we change the default value too?

[0001-Respect-customized-cursor-face-in-cua-mode.patch (text/x-patch, attachment)]

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