Revert "Add new command 'toggle-theme'"

This reverts commit f31b9d86a6.

doc/emacs/custom.texi

@@ -667,11 +667,6 @@ type @kbd{M-x disable-theme}.
 the @file{*Custom Themes*} buffer; or type @kbd{M-x describe-theme}
 anywhere in Emacs and enter the theme name.
 
-@findex toggle-theme
-  Some themes have dual variants (most often these are light and dark
-pairs).  You can switch between these by typing @kbd{M-x
-toggle-theme}.  Note that this only works if only one theme is active.
-
 @node Creating Custom Themes
 @subsection Creating Custom Themes
 @cindex custom themes, creating

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: 20220906.2016
+;; Version: 20220202.1126
 ;; Keywords: color theme
 
 ;; This file is part of GNU Emacs.
@@ -1083,8 +1083,6 @@ more...")
   (add-to-list 'custom-theme-load-path
                (file-name-as-directory (file-name-directory load-file-name))))
 
-(put 'leuven-dark 'dual-theme 'leuven) ;see `toggle-theme'
-
 (provide-theme 'leuven-dark)
 
 ;; This is for the sake of Emacs.

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: 20220906.2016
+;; Version: 20200513.1928
 ;; Keywords: color theme
 
 ;; This file is part of GNU Emacs.
@@ -1065,8 +1065,6 @@ more...")
   (add-to-list 'custom-theme-load-path
                (file-name-as-directory (file-name-directory load-file-name))))
 
-(put 'leuven 'dual-theme 'leuven-dark) ;see `toggle-theme'
-
 (provide-theme 'leuven)
 
 ;; This is for the sake of Emacs.

etc/themes/tango-dark-theme.el

@@ -190,8 +190,6 @@ Semantic, and Ansi-Color faces are included.")
    `(ansi-color-bright-white ((,class (:background ,alum-1
 				       :foreground ,alum-1))))))
 
-(put 'tango-dark 'dual-theme 'tango) ;see `toggle-theme'
-
 (provide-theme 'tango-dark)
 
 ;;; tango-dark-theme.el ends here

etc/themes/tango-theme.el

@@ -173,8 +173,6 @@ Semantic, and Ansi-Color faces are included.")
    `(ansi-color-bright-white ((,class (:background ,alum-1
 				       :foreground ,alum-1))))))
 
-(put 'tango 'dual-theme 'tango-dark) ;see `toggle-theme'
-
 (provide-theme 'tango)
 
 ;;; tango-theme.el ends here

etc/themes/tsdh-dark-theme.el

@@ -142,8 +142,6 @@
  '(widget-field ((t (:box (:line-width 2 :color "grey75" :style pressed-button)))))
  '(window-number-face ((t (:foreground "red" :weight bold)))))
 
-(put 'tsdh-dark 'dual-theme 'tsdh-light) ;see `toggle-theme'
-
 (provide-theme 'tsdh-dark)
 
 ;;; tsdh-dark-theme.el ends here

etc/themes/tsdh-light-theme.el

@@ -104,8 +104,6 @@ Used and created by Tassilo Horn.")
  '(show-paren-mismatch ((t (:background "deep pink" :weight bold))))
  '(window-number-face ((t (:foreground "red" :weight bold)))))
 
-(put 'tsdh-light 'dual-theme 'tsdh-dark) ;see `toggle-theme'
-
 (provide-theme 'tsdh-light)
 
 ;;; tsdh-light-theme.el ends here

lisp/cus-theme.el

@@ -515,8 +515,6 @@ It includes all faces in list FACES."
 			  (end-of-file nil)))))
             (and (eq (car-safe sexp) 'deftheme)
 		 (setq doc (nth 2 sexp)))))))
-    (when-let ((dual (get theme 'dual-theme)))
-      (princ (format " The dual theme is `%s'" dual)))
     (princ "\n\nDocumentation:\n")
     (princ (if (stringp doc)
 	       (substitute-command-keys doc)

lisp/custom.el

@@ -1372,25 +1372,6 @@ Return t if THEME was successfully loaded, nil otherwise."
     (enable-theme theme))
   t)
 
-(defun toggle-theme (&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))
-         (dual (get theme 'dual-theme)))
-    (unless dual
-      (error "`%s' has no dual theme to toggle between" theme))
-    (disable-theme theme)
-    (load-theme dual no-confirm no-enable)))
-
 (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,