emacs: Split 'guix-param-titles' variable.

Generate 'guix-ENTRY-TYPE-BUFFER-TYPE-titles' variables for each
ENTRY-TYPE and BUFFER-TYPE instead.

* emacs/guix-base.el (guix-param-titles): Remove.
  (guix-buffer-data): New variable.
  (guix-buffer-value, guix-buffer-param-title): New procedures.
  (guix-buffer-define-interface): Add ':titles' keyword.
* emacs/guix-info.el (guix-info-param-title): Adjust accordingly.
* emacs/guix-list.el (guix-list-param-title): Likewise.
  (guix-list-column-titles): Remove.
* doc/emacs.texi (Emacs Appearance): Adjust accordingly.

doc/emacs.texi

@@ -480,11 +480,12 @@ the following variables (@dfn{ENTRY-TYPE} means @code{package},
 
 @table @code
 @item guix-ENTRY-TYPE-list-format
-@itemx guix-list-column-titles
+@itemx guix-ENTRY-TYPE-list-titles
 Specify the columns, their names, what and how is displayed in ``list''
 buffers.
 
 @item guix-ENTRY-TYPE-info-format
+@itemx guix-ENTRY-TYPE-info-titles
 @itemx guix-info-ignore-empty-values
 @itemx guix-info-param-title-format
 @itemx guix-info-multiline-prefix

emacs/guix-base.el

@@ -39,28 +39,6 @@
 
 ;;; Parameters of the entries
 
-(defvar guix-param-titles
-  '((package
-     (home-url          . "Home page"))
-    (installed
-     (path              . "Installed path"))
-    (output
-     (home-url          . "Home page")
-     (path              . "Installed path"))
-    (generation
-     (prev-number       . "Previous number")))
-  "List for defining titles of entry parameters.
-Titles are used for displaying information about entries.
-Each element of the list has a form:
-
-  (ENTRY-TYPE . ((PARAM . TITLE) ...))")
-
-(defun guix-get-param-title (entry-type param)
-  "Return title of an ENTRY-TYPE entry parameter PARAM."
-  (or (guix-assq-value guix-param-titles
-                       entry-type param)
-      (guix-symbol-title param)))
-
 (defun guix-package-name-specification (name version &optional output)
   "Return Guix package specification by its NAME, VERSION and OUTPUT."
   (concat name "-" version
@@ -278,6 +256,25 @@ See `guix-update-after-operation' for details."
 
 ;;; Common definitions for buffer types
 
+(defvar guix-buffer-data nil
+  "Alist with 'buffer' data.
+This alist is filled by `guix-buffer-define-interface' macro.")
+
+(defun guix-buffer-value (buffer-type entry-type symbol)
+  "Return SYMBOL's value for BUFFER-TYPE/ENTRY-TYPE from `guix-buffer-data'."
+  (symbol-value
+   (guix-assq-value guix-buffer-data buffer-type entry-type symbol)))
+
+(defun guix-buffer-param-title (buffer-type entry-type param)
+  "Return PARAM title for BUFFER-TYPE/ENTRY-TYPE."
+  (or (guix-assq-value (guix-buffer-value buffer-type entry-type 'titles)
+                       param)
+      ;; Fallback to a title defined in 'info' interface.
+      (unless (eq buffer-type 'info)
+        (guix-assq-value (guix-buffer-value 'info entry-type 'titles)
+                         param))
+      (guix-symbol-title param)))
+
 (defvar guix-root-map
   (let ((map (make-sparse-keymap)))
     (define-key map (kbd "l") 'guix-history-back)
@@ -354,13 +351,17 @@ Optional keywords:
   - `:buffer-name' - default value of the generated
     `guix-TYPE-buffer-name' variable.
 
+  - `:titles' - default value of the generated
+    `guix-TYPE-titles' variable.
+
   - `:history-size' - default value of the generated
     `guix-TYPE-history-size' variable.
 
   - `:revert-confirm?' - default value of the generated
     `guix-TYPE-revert-confirm' variable.
 
-  - `:reduced?' - if non-nil, generate only group and faces group."
+  - `:reduced?' - if non-nil, generate only group, faces group
+    and titles variable."
   (declare (indent 2))
   (let* ((entry-type-str     (symbol-name entry-type))
          (buffer-type-str    (symbol-name buffer-type))
@@ -377,12 +378,14 @@ Optional keywords:
          (mode               (intern (concat prefix "-mode")))
          (mode-init-fun      (intern (concat prefix "-mode-initialize")))
          (buffer-name-var    (intern (concat prefix "-buffer-name")))
+         (titles-var         (intern (concat prefix "-titles")))
          (history-size-var   (intern (concat prefix "-history-size")))
          (revert-confirm-var (intern (concat prefix "-revert-confirm"))))
     (guix-keyword-args-let args
         ((buffer-name-val    :buffer-name
                              (format "*Guix %s %s*"
                                      Entry-type-str Buffer-type-str))
+         (titles-val         :titles)
          (history-size-val   :history-size 20)
          (revert-confirm-val :revert-confirm? t)
          (reduced?           :reduced?))
@@ -398,6 +401,12 @@ Optional keywords:
                     entry-type-str buffer-type-str)
            :group ',(intern (concat "guix-" buffer-type-str "-faces")))
 
+         (defcustom ,titles-var ,titles-val
+           ,(format "Alist of titles of '%s' parameters."
+                    entry-type-str)
+           :type '(alist :key-type symbol :value-type string)
+           :group ',group)
+
          ,(unless reduced?
             `(progn
                (defcustom ,buffer-name-var ,buffer-name-val
@@ -429,7 +438,11 @@ If non-nil, ask to confirm for reverting `%S' buffer."
                           "\\{" mode-map-str "}")
                  (setq-local revert-buffer-function 'guix-revert-buffer)
                  (setq-local guix-history-size ,history-size-var)
-                 (and (fboundp ',mode-init-fun) (,mode-init-fun)))))))))
+                 (and (fboundp ',mode-init-fun) (,mode-init-fun)))))
+
+         (guix-alist-put!
+          ',titles-var 'guix-buffer-data
+          ',buffer-type ',entry-type 'titles)))))
 
 
 ;;; Getting and displaying info about packages and generations

emacs/guix-info.el

@@ -127,7 +127,7 @@ This alist is filled by `guix-info-define-interface' macro.")
 
 (defun guix-info-param-title (entry-type param)
   "Return a title of an ENTRY-TYPE parameter PARAM."
-  (guix-get-param-title entry-type param))
+  (guix-buffer-param-title 'info entry-type param))
 
 (defun guix-info-format (entry-type)
   "Return 'info' format for ENTRY-TYPE."
@@ -486,11 +486,13 @@ After calling each METHOD, a new line is inserted."
             (native-inputs format (format guix-package-native-input))
             (propagated-inputs format
                                (format guix-package-propagated-input)))
+  :titles '((home-url . "Home page"))
   :required '(id name version installed non-unique))
 
 (guix-info-define-interface installed-output
   :format '((path simple (indent guix-file))
             (dependencies simple (indent guix-file)))
+  :titles '((path . "Store directory"))
   :reduced? t)
 
 (defface guix-package-info-heading
@@ -794,6 +796,7 @@ This function is used to hide a \"Download\" button if needed."
             (propagated-inputs format
                                (format guix-package-propagated-input))
             (description simple (indent guix-package-info-description)))
+  :titles guix-package-info-titles
   :required '(id package-id installed non-unique))
 
 (defun guix-output-info-insert-version (version entry)
@@ -827,7 +830,9 @@ This function is used to hide a \"Download\" button if needed."
             (prev-number format (format))
             (current format guix-generation-info-insert-current)
             (path simple (indent guix-file))
-            (time format (time))))
+            (time format (time)))
+  :titles '((path . "File name")
+            (prev-number . "Previous number")))
 
 (defface guix-generation-info-number
   '((t :inherit font-lock-keyword-face))

emacs/guix-list.el

@@ -52,13 +52,6 @@
   "Face used for time stamps."
   :group 'guix-list-faces)
 
-(defvar guix-list-column-titles
-  '((generation
-     (number . "N.")))
-  "Column titles for list buffers.
-Has the same structure as `guix-param-titles', but titles from
-this list have a priority.")
-
 (defun guix-list-describe (&optional mark-names)
   "Describe entries marked with a general mark.
 'Describe' means display entries in 'info' buffer.
@@ -87,9 +80,7 @@ This alist is filled by `guix-list-define-interface' macro.")
 
 (defun guix-list-param-title (entry-type param)
   "Return column title of an ENTRY-TYPE parameter PARAM."
-  (or (guix-assq-value guix-list-column-titles
+  (guix-buffer-param-title 'list entry-type param))
-                       entry-type param)
-      (guix-get-param-title entry-type param)))
 
 (defun guix-list-format (entry-type)
   "Return column format for ENTRY-TYPE."
@@ -816,6 +807,7 @@ See `guix-package-info-type'."
             (current guix-generation-list-get-current 10 t)
             (time guix-list-get-time 20 t)
             (path guix-list-get-file-path 30 t))
+  :titles '((number . "N."))
   :sort-key '(number . t)
   :marks '((delete . ?D)))