Re: Suggestions for improvements to the *Completions* buffer

[Philip Kaludercic]

Juri Linkov <juri@linkov.net> writes:

>>>> The mechanism used to make backtab in the minibuffer switch to the last
>>>> completion option is not that nice as it uses this-command and
>>>> this-command-keys.
>>>
>>> When completion-auto-select is not enabled, TAB scrolls the completions 
>>> buffer
>>> forward.  So S-TAB (backtab) could scroll backward.
>>>
>>> When completion-auto-select will be enabled, backtab could switch to
>>> the completions as well, indeed.
>>
>> How is this?
>
> Thanks, this has now such a nice property that after typing TAB
> that switches to the completions buffer, it's easy to switch back
> to the minibuffer by typing S-TAB.  But this works only when
> completion-wrap-movement is non-nil.

True, even that was not the primary intention.  I guess this also raises
the question of whether or not completion-wrap-movement and
completion-auto-select should be set to non-nil by default or not?  If
applied, maybe they could be enabled for a month or so, to gather
experiences and then decide how to continue on that basis.

>> +(defcustom completion-wrap-movement t
>> +  "Non-nil means to wrap around when selecting completion options.
>> +This affects the commands `next-completion' and
>> +`previous-completion'."
>> +  :type 'boolean
>> +  :version "29.1"
>> +  :group 'completion)
>
> It seems now completion-wrap-movement has no effect:
> typing n, p, <right> or <left> eventually switches to the minibuffer,
> where continuing typing these keys uses other commands.

True, the only way I see right now to avoid this would be to check if
tab/backtab was used before switching to the minibuffer, and otherwise
wrap within the completions buffer.

>> (completion--in-region-1): Handle backtab to scroll backwards
>> @@ -1386,7 +1386,9 @@ completion--in-region-1
>>              (set-window-start window (point-min) nil)
>>            ;; Else scroll down one screen.
>>            (with-selected-window window
>> -        (scroll-up)))
>> +            (if (equal (this-command-keys) [backtab])
>> +                (scroll-down)
>> +              (scroll-up))))
>
> Using S-TAB to scroll backwards also works nice.
> The only difference with TAB is that while typing
> several TABs reaches the end of the completions buffer,
> typing more TABs wraps to the beginning of the completions
> buffer, but S-TAB doesn't wrap to the end of the buffer.

Good point, this should fix that:

>From 6155e4a3347a9f7d188eae125d71040b8c8dcdf2 Mon Sep 17 00:00:00 2001
From: Philip Kaludercic <philipk@posteo.net>
Date: Thu, 9 Dec 2021 17:26:14 +0100
Subject: [PATCH] Allow for next-completion to wrap around the completion
 buffer

* lisp/simple.el (completion-wrap-movement): Add new option.
(previous-completion): Update docstring.
(next-completion): Respect completion-wrap-movement.
(switch-to-completions): Handle backwards completion by jumping to the
end of the buffer.
* lisp/minibuffer.el: (minibuffer-local-completion-map): Bind
minibuffer-complete to backtab
(completion--in-region-1): Handle backtab to scroll backwards
---
 lisp/minibuffer.el | 15 ++++++---
 lisp/simple.el     | 81 ++++++++++++++++++++++++++++++----------------
 2 files changed, 63 insertions(+), 33 deletions(-)

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 28bd1df59a..112c609a0a 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1379,14 +1379,18 @@ completion--in-region-1
    ;; and this command is repeated, scroll that window.
    ((and (window-live-p minibuffer-scroll-window)
          (eq t (frame-visible-p (window-frame minibuffer-scroll-window))))
-    (let ((window minibuffer-scroll-window))
+    (let ((window minibuffer-scroll-window)
+          (reverse (equal (this-command-keys) [backtab])))
       (with-current-buffer (window-buffer window)
-        (if (pos-visible-in-window-p (point-max) window)
-            ;; If end is in view, scroll up to the beginning.
-            (set-window-start window (point-min) nil)
+        (if (pos-visible-in-window-p (if reverse (point-min) (point-max)) 
window)
+            ;; If end or beginning is in view, scroll up to the
+            ;; beginning or end respectively.
+            (if reverse
+                (set-window-point window (point-max))
+              (set-window-start window (point-min) nil))
           ;; Else scroll down one screen.
           (with-selected-window window
-           (scroll-up)))
+            (if reverse (scroll-down) (scroll-up))))
         nil)))
    ;; If we're cycling, keep on cycling.
    ((and completion-cycling completion-all-sorted-completions)
@@ -2651,6 +2655,7 @@ minibuffer-local-completion-map
   (let ((map (make-sparse-keymap)))
     (set-keymap-parent map minibuffer-local-map)
     (define-key map "\t" 'minibuffer-complete)
+    (define-key map [backtab] 'minibuffer-complete)
     ;; M-TAB is already abused for many other purposes, so we should find
     ;; another binding for it.
     ;; (define-key map "\e\t" 'minibuffer-force-complete)
diff --git a/lisp/simple.el b/lisp/simple.el
index d0e58575e1..626c24e10d 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -9027,38 +9027,57 @@ delete-completion-window
       (if (get-buffer-window buf)
          (select-window (get-buffer-window buf))))))
 
+(defcustom completion-wrap-movement t
+  "Non-nil means to wrap around when selecting completion options.
+This affects the commands `next-completion' and
+`previous-completion'."
+  :type 'boolean
+  :version "29.1"
+  :group 'completion)
+
 (defun previous-completion (n)
-  "Move to the previous item in the completion list."
+  "Move to the previous item in the completion list.
+With prefix argument N, move back N items (negative N means move
+forward)."
   (interactive "p")
   (next-completion (- n)))
 
 (defun next-completion (n)
   "Move to the next item in the completion list.
-With prefix argument N, move N items (negative N means move backward)."
+With prefix argument N, move N items (negative N means move
+backward)."
   (interactive "p")
   (let ((beg (point-min)) (end (point-max)))
-    (while (and (> n 0) (not (eobp)))
-      ;; If in a completion, move to the end of it.
-      (when (get-text-property (point) 'mouse-face)
-       (goto-char (next-single-property-change (point) 'mouse-face nil end)))
-      ;; Move to start of next one.
-      (unless (get-text-property (point) 'mouse-face)
-       (goto-char (next-single-property-change (point) 'mouse-face nil end)))
-      (setq n (1- n)))
-    (while (and (< n 0) (not (bobp)))
-      (let ((prop (get-text-property (1- (point)) 'mouse-face)))
-       ;; If in a completion, move to the start of it.
-       (when (and prop (eq prop (get-text-property (point) 'mouse-face)))
-         (goto-char (previous-single-property-change
-                     (point) 'mouse-face nil beg)))
-       ;; Move to end of the previous completion.
-       (unless (or (bobp) (get-text-property (1- (point)) 'mouse-face))
-         (goto-char (previous-single-property-change
-                     (point) 'mouse-face nil beg)))
-       ;; Move to the start of that one.
-       (goto-char (previous-single-property-change
-                   (point) 'mouse-face nil beg))
-       (setq n (1+ n))))))
+    (catch 'bound
+      (while (> n 0)
+        ;; If in a completion, move to the end of it.
+        (when (get-text-property (point) 'mouse-face)
+          (goto-char (next-single-property-change (point) 'mouse-face nil 
end)))
+        (when (and completion-wrap-movement (eobp))
+          (throw 'bound nil))
+        ;; Move to start of next one.
+        (unless (get-text-property (point) 'mouse-face)
+          (goto-char (next-single-property-change (point) 'mouse-face nil 
end)))
+        (setq n (1- n)))
+      (while (< n 0)
+        (let ((prop (get-text-property (1- (point)) 'mouse-face)))
+          ;; If in a completion, move to the start of it.
+          (when (and prop (eq prop (get-text-property (point) 'mouse-face)))
+            (goto-char (previous-single-property-change
+                        (point) 'mouse-face nil beg)))
+          ;; Move to end of the previous completion.
+          (unless (or (bobp) (get-text-property (1- (point)) 'mouse-face))
+            (goto-char (previous-single-property-change
+                        (point) 'mouse-face nil beg)))
+          (when (and completion-wrap-movement (bobp))
+            (goto-char (next-single-property-change (point) 'mouse-face nil 
end))
+            (throw 'bound nil))
+          ;; Move to the start of that one.
+          (goto-char (previous-single-property-change
+                      (point) 'mouse-face nil beg))
+          (setq n (1+ n)))))
+    (when (/= 0 n)
+      (switch-to-minibuffer))))
 
 (defun choose-completion (&optional event)
   "Choose the completion at point.
@@ -9283,10 +9302,16 @@ switch-to-completions
                            (get-buffer-window "*Completions*" 0)))))
     (when window
       (select-window window)
-      ;; In the new buffer, go to the first completion.
-      ;; FIXME: Perhaps this should be done in `minibuffer-completion-help'.
-      (when (bobp)
-       (next-completion 1)))))
+      (cond
+       ((and (memq this-command '(completion-at-point minibuffer-complete))
+             (equal (this-command-keys) [backtab])
+             (bobp))
+        (goto-char (point-max))
+        (previous-completion 1))
+       ;; In the new buffer, go to the first completion.
+       ;; FIXME: Perhaps this should be done in `minibuffer-completion-help'.
+       ((bobp)
+        (next-completion 1))))))
 
 (defun read-expression-switch-to-completions ()
   "Select the completion list window while reading an expression."
-- 
2.30.2

-- 
        Philip Kaludercic