bug#57639: [PATCH] Add new command 'toggle-theme'

[Philip Kaludercic <philipk@posteo.net>]

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Lars Ingebrigtsen <larsi@gnus.org> writes:

> Philip Kaludercic <philipk@posteo.net> writes:
>
>>> Code exists for both Windows and Macos in the bug tracker somewhere, but
>>> haven't been integrated yet because nobody has sat down to make a
>>> consistent interface across all the platforms.
>>
>> What about GNU/Linux desktops?
>
> I thought we already had support for this under Gtk?  But I may be
> misremembering.

Am I reading it correctly that `style_changed_cb' in gtkutils.c would be
a place to start looking for this functionality?

>> Stefans Gruvbox example had multiple dark and light variants.  E.g.
>> Would the new command toggle from `gruvbox-dark-soft' to
>> `gruvbox-dark-light' or prompt the user to select from all the gruvbox
>> themes?
>
> Yes, but if you have the soft gruvbox active, you don't want to switch
> to the hard one when changing between dark/light, so there's no ambiguity.

So would gruvbox-soft-dark have all the other themes as variants or only
gruvbox-soft-dark?  

>>> But now I see that you've pushed `toggle-theme'...  *sigh*
>>
>> I'm very sorry about that, I've reverted those commits, since they were
>> accidentally pushed!
>
> *phew*  Thanks.  😀

Here is an updated version:


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From 1c9f1d92d0ecc4c7b94772e3a15ebf5e577a7f3d Mon Sep 17 00:00:00 2001
From: Philip Kaludercic <philipk@posteo.net>
Date: Tue, 6 Sep 2022 20:53:35 +0200
Subject: [PATCH] Add new command 'theme-choose-variant'

* doc/emacs/custom.texi (Custom Themes): Mention it.
* etc/themes/leuven-dark-theme.el (leuven-dark): Add dual theme.
* etc/themes/leuven-theme.el (leuven): Add dual theme.
* etc/themes/tango-dark-theme.el (tango-dark): Add dual theme.
* etc/themes/tango-theme.el (tango): Add dual theme.
* etc/themes/tsdh-dark-theme.el (tsdh-dark): Add dual theme.
* etc/themes/tsdh-light-theme.el (tsdh-light): Add dual theme.
* lisp/cus-theme.el (describe-theme-1): Say if a theme has a dual.
* lisp/custom.el (theme-choose-variant): Add new command.
(toggle-theme): Add an alias.  (Bug#57639)
---
 doc/emacs/custom.texi           |  8 ++++++++
 etc/themes/leuven-dark-theme.el |  4 +++-
 etc/themes/leuven-theme.el      |  4 +++-
 etc/themes/tango-dark-theme.el  |  2 ++
 etc/themes/tango-theme.el       |  2 ++
 etc/themes/tsdh-dark-theme.el   |  2 ++
 etc/themes/tsdh-light-theme.el  |  2 ++
 lisp/cus-theme.el               |  5 +++++
 lisp/custom.el                  | 27 +++++++++++++++++++++++++++
 9 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/doc/emacs/custom.texi b/doc/emacs/custom.texi
index ff7ab83190..f86c7e2dd9 100644
--- a/doc/emacs/custom.texi
+++ b/doc/emacs/custom.texi
@@ -667,6 +667,14 @@ Custom Themes
 the @file{*Custom Themes*} buffer; or type @kbd{M-x describe-theme}
 anywhere in Emacs and enter the theme name.
 
+@findex theme-choose-variant
+  Some themes have variants (most often these are light and dark
+pairs).  You can switch between these by typing @kbd{M-x
+theme-choose-variant}.  Note that this only works if only one theme is
+active.  If a theme has only one alternative, it will toggle
+automatically.  If there are more of them, it will query which one to
+use.
+
 @node Creating Custom Themes
 @subsection Creating Custom Themes
 @cindex custom themes, creating
diff --git a/etc/themes/leuven-dark-theme.el b/etc/themes/leuven-dark-theme.el
index 0e162c8bab..dfcd64a11c 100644
--- a/etc/themes/leuven-dark-theme.el
+++ b/etc/themes/leuven-dark-theme.el
@@ -5,7 +5,7 @@
 ;; Author: Fabrice Niessen <(concat "fniessen" at-sign "pirilampo.org")>
 ;; Contributor: Thibault Polge <(concat "thibault" at-sign "thb.lt")>
 ;; URL: https://github.com/fniessen/emacs-leuven-dark-theme
-;; Version: 20220202.1126
+;; Version: 20220911.1858
 ;; Keywords: color theme
 
 ;; This file is part of GNU Emacs.
@@ -1083,6 +1083,8 @@ leuven-dark
   (add-to-list 'custom-theme-load-path
                (file-name-as-directory (file-name-directory load-file-name))))
 
+(put 'leuven-dark 'theme-variants 'leuven) ;see `toggle-theme'
+
 (provide-theme 'leuven-dark)
 
 ;; This is for the sake of Emacs.
diff --git a/etc/themes/leuven-theme.el b/etc/themes/leuven-theme.el
index d9a8d5391a..66a65bc0b3 100644
--- a/etc/themes/leuven-theme.el
+++ b/etc/themes/leuven-theme.el
@@ -4,7 +4,7 @@
 
 ;; Author: Fabrice Niessen <(concat "fniessen" at-sign "pirilampo.org")>
 ;; URL: https://github.com/fniessen/emacs-leuven-theme
-;; Version: 20200513.1928
+;; Version: 20220911.1858
 ;; Keywords: color theme
 
 ;; This file is part of GNU Emacs.
@@ -1065,6 +1065,8 @@ leuven
   (add-to-list 'custom-theme-load-path
                (file-name-as-directory (file-name-directory load-file-name))))
 
+(put 'leuven 'theme-variants 'leuven-dark) ;see `toggle-theme'
+
 (provide-theme 'leuven)
 
 ;; This is for the sake of Emacs.
diff --git a/etc/themes/tango-dark-theme.el b/etc/themes/tango-dark-theme.el
index ef00d2ac49..81b7cbde13 100644
--- a/etc/themes/tango-dark-theme.el
+++ b/etc/themes/tango-dark-theme.el
@@ -190,6 +190,8 @@ tango-dark
    `(ansi-color-bright-white ((,class (:background ,alum-1
 				       :foreground ,alum-1))))))
 
+(put 'tango-dark 'theme-variants 'tango) ;see `toggle-theme'
+
 (provide-theme 'tango-dark)
 
 ;;; tango-dark-theme.el ends here
diff --git a/etc/themes/tango-theme.el b/etc/themes/tango-theme.el
index ecbbf03753..7f53a5cce2 100644
--- a/etc/themes/tango-theme.el
+++ b/etc/themes/tango-theme.el
@@ -173,6 +173,8 @@ tango
    `(ansi-color-bright-white ((,class (:background ,alum-1
 				       :foreground ,alum-1))))))
 
+(put 'tango 'theme-variants 'tango-dark) ;see `toggle-theme'
+
 (provide-theme 'tango)
 
 ;;; tango-theme.el ends here
diff --git a/etc/themes/tsdh-dark-theme.el b/etc/themes/tsdh-dark-theme.el
index a88ad75520..aef8cae3e0 100644
--- a/etc/themes/tsdh-dark-theme.el
+++ b/etc/themes/tsdh-dark-theme.el
@@ -142,6 +142,8 @@ tsdh-dark
  '(widget-field ((t (:box (:line-width 2 :color "grey75" :style pressed-button)))))
  '(window-number-face ((t (:foreground "red" :weight bold)))))
 
+(put 'tsdh-dark 'theme-variants 'tsdh-light) ;see `toggle-theme'
+
 (provide-theme 'tsdh-dark)
 
 ;;; tsdh-dark-theme.el ends here
diff --git a/etc/themes/tsdh-light-theme.el b/etc/themes/tsdh-light-theme.el
index d9d09b702b..d0f11f272b 100644
--- a/etc/themes/tsdh-light-theme.el
+++ b/etc/themes/tsdh-light-theme.el
@@ -104,6 +104,8 @@ tsdh-light
  '(show-paren-mismatch ((t (:background "deep pink" :weight bold))))
  '(window-number-face ((t (:foreground "red" :weight bold)))))
 
+(put 'tsdh-light 'theme-variants 'tsdh-dark) ;see `toggle-theme'
+
 (provide-theme 'tsdh-light)
 
 ;;; tsdh-light-theme.el ends here
diff --git a/lisp/cus-theme.el b/lisp/cus-theme.el
index 90680ff68f..dcd562c6af 100644
--- a/lisp/cus-theme.el
+++ b/lisp/cus-theme.el
@@ -515,6 +515,11 @@ describe-theme-1
 			  (end-of-file nil)))))
             (and (eq (car-safe sexp) 'deftheme)
 		 (setq doc (nth 2 sexp)))))))
+    (when-let ((variants (get theme 'theme-variants)))
+      (princ (concat " Variants of this theme are "
+                     (mapconcat
+                      (lambda (th) (concat "`" th "'"))
+                      variants ", "))))
     (princ "\n\nDocumentation:\n")
     (princ (if (stringp doc)
 	       (substitute-command-keys doc)
diff --git a/lisp/custom.el b/lisp/custom.el
index 352b5b0e16..58f8d05ec6 100644
--- a/lisp/custom.el
+++ b/lisp/custom.el
@@ -1372,6 +1372,33 @@ load-theme
     (enable-theme theme))
   t)
 
+(defun theme-choose-variant (&optional no-confirm no-enable)
+  "Toggle the current active theme by enabling its dual pair.
+The current theme will be immediately disabled before the dual
+theme has been enabled.  If THEME is not active an error will be
+raised.  If theme is nil For NO-CONFIRM and NO-ENABLE, see
+`load-theme'."
+  (interactive)
+  (cond
+   ((length= custom-enabled-themes 0)
+    (user-error "No theme is active, cannot toggle"))
+   ((length> custom-enabled-themes 1)
+    (user-error "More than one theme active, cannot unambiguously toggle")))
+  (let ((theme (car custom-enabled-themes)) variants)
+    (dolist (variant (ensure-list (get theme 'theme-variants)))
+      (when (and (custom-theme-p theme) (not (eq variant theme)))
+        (push variant variants)))
+    (let ((choice (cond
+                   ((null variants)
+                    (error "`%s' has no variants" theme))
+                   ((length= variants 1)
+                    (car variants))
+                   ((intern (completing-read "Load custom theme: " variants))))))
+      (disable-theme theme)
+      (load-theme choice no-confirm no-enable))))
+
+(defalias 'toggle-theme #'theme-choose-variant)
+
 (defun custom-theme-load-confirm (hash)
   "Query the user about loading a Custom theme that may not be safe.
 The theme should be in the current buffer.  If the user agrees,
-- 
2.37.3