New commands previous-line-completion and next-line-completion (bug#59486)

* lisp/simple.el (completion-list-mode-map): Bind [up] to
'previous-line-completion', and [down] to 'next-line-completion'.
(completion-auto-wrap): Mention `next-line-completion' and
`previous-line-completion' in the docstring.
(previous-line-completion, next-line-completion): New commands.

etc/NEWS

@@ -1757,9 +1757,10 @@ the second one will switch to the "*Completions*" buffer.
 
 ---
 *** New user option 'completion-auto-wrap'.
-When non-nil, the commands 'next-completion' and 'previous-completion'
+When non-nil, the commands 'next-completion', 'previous-completion',
-automatically wrap around on reaching the beginning or the end of
+'next-line-completion' and 'previous-line-completion' automatically
-the "*Completions*" buffer.
+wrap around on reaching the beginning or the end of the "*Completions*"
+buffer.
 
 +++
 *** New values for the 'completion-auto-help' user option.

lisp/simple.el

@@ -9572,6 +9572,8 @@ makes it easier to edit it."
     (define-key map "\C-m" 'choose-completion)
     (define-key map "\e\e\e" 'delete-completion-window)
     (define-key map [remap keyboard-quit] #'delete-completion-window)
+    (define-key map [up] 'previous-line-completion)
+    (define-key map [down] 'next-line-completion)
     (define-key map [left] 'previous-completion)
     (define-key map [right] 'next-completion)
     (define-key map [?\t] 'next-completion)
@@ -9631,8 +9633,10 @@ Go to the window from which completion was requested."
 
 (defcustom completion-auto-wrap t
   "Non-nil means to wrap around when selecting completion options.
-This affects the commands `next-completion' and `previous-completion'.
+This affects the commands `next-completion', `previous-completion',
-When `completion-auto-select' is t, it wraps through the minibuffer."
+`next-line-completion' and `previous-line-completion'.
+When `completion-auto-select' is t, it wraps through the minibuffer
+for the commands bound to the TAB key."
   :type 'boolean
   :version "29.1"
   :group 'completion)
@@ -9736,6 +9740,73 @@ Also see the `completion-auto-wrap' variable."
     (when (/= 0 n)
       (switch-to-minibuffer))))
 
+(defun previous-line-completion (&optional n)
+  "Move to the item on the previous line in the completion list.
+With prefix argument N, move back N items line-wise (negative N
+means move forward).
+
+Also see the `completion-auto-wrap' variable."
+  (interactive "p")
+  (next-line-completion (- n)))
+
+(defun next-line-completion (&optional n)
+  "Move to the item on the next line in the completion list.
+With prefix argument N, move N items line-wise (negative N
+means move backward).
+
+Also see the `completion-auto-wrap' variable."
+  (interactive "p")
+  (let ((column (current-column))
+        pos)
+    (catch 'bound
+      (while (> n 0)
+        (setq pos nil)
+        (save-excursion
+          (while (and (not pos) (not (eobp)))
+            (forward-line 1)
+            (when (and (not (eobp))
+                       (eq (move-to-column column) column)
+                       (get-text-property (point) 'mouse-face))
+              (setq pos (point)))))
+        (if pos (goto-char pos)
+          (when completion-auto-wrap
+            (save-excursion
+              (goto-char (point-min))
+              (when (and (eq (move-to-column column) column)
+                         (get-text-property (point) 'mouse-face))
+                (setq pos (point)))
+              (while (and (not pos) (not (eobp)))
+                (forward-line 1)
+                (when (and (eq (move-to-column column) column)
+                           (get-text-property (point) 'mouse-face))
+                  (setq pos (point)))))
+            (if pos (goto-char pos))))
+        (setq n (1- n)))
+
+      (while (< n 0)
+        (setq pos nil)
+        (save-excursion
+          (while (and (not pos) (not (bobp)))
+            (forward-line -1)
+            (when (and (not (bobp))
+                       (eq (move-to-column column) column)
+                       (get-text-property (point) 'mouse-face))
+              (setq pos (point)))))
+        (if pos (goto-char pos)
+          (when completion-auto-wrap
+            (save-excursion
+              (goto-char (point-max))
+              (when (and (eq (move-to-column column) column)
+                         (get-text-property (point) 'mouse-face))
+                (setq pos (point)))
+              (while (and (not pos) (not (bobp)))
+                (forward-line -1)
+                (when (and (eq (move-to-column column) column)
+                           (get-text-property (point) 'mouse-face))
+                  (setq pos (point)))))
+            (if pos (goto-char pos))))
+        (setq n (1+ n))))))
+
 (defun choose-completion (&optional event no-exit no-quit)
   "Choose the completion at point.
 If EVENT, use EVENT's position to determine the starting position.