Re: vertical fido-mode

[Ergus via "Emacs development discussions." <emacs-devel@gnu.org>]

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On Thu, Jun 11, 2020 at 02:08:56AM +0300, Juri Linkov wrote:

>Or show vertical completions in the *Completions* buffer and use the
>current icomplete keys to navigate the *Completions* list from the minibuffer.
>

Hi!

Coming back to this thread, I just made this very simple patch
(attached) to provide a sort of "zsh" like experience in the
*Completion* buffer.

I would love to see a version of this enabled by default in emacs (to
feel we are a bit in 2020 and give a more friendly first impression to
new users); but I know that changing defaults will start a war. So I
won't even try to argue about that; so I added variables to customize
everything.

If you are interested, you can try it and I will be very happy with any
suggestions and critics if you thing this can be added to master in the
future.

It basically adds:

1) enforces navigation throw completion candidates (no go to header or
random useless places in *completion* buffer).

2) Current candidate highlight with the 'highlight face.

3) Second tab in minibuffer with completion shown and all candidates
visible (no need scroll) jump to *Completions* buffer (similar to zsh).

4) Skip Completion buffer with C-g.

The intentions of this is just to tweak a little the *Completions*
interaction keeping everything extremely simple.

At the end after a couple of hours most of the users go for Ido, help or
Ivy. But this doesn't mean we shouldn't improve the first impression
right?

OTOH: I would like to know if Omar finally got the copyright otherwise I
will try to implement the vertical-fido/Icompletes mode.

Best,
Ergus


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diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 641a2e5315..7c5025b11c 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -753,6 +753,12 @@ minibuffer-message-clear-timeout
                  (integer :tag "Wait for the number of seconds" 2))
   :version "27.1")
 
+(defcustom minibuffer-tab-go-completion t
+  "If a second `TAB' jump to completion buffer."
+  :type 'boolean
+  :version "28.1"
+  :group 'completion)
+
 (defvar minibuffer-message-timer nil)
 (defvar minibuffer-message-overlay nil)
 
@@ -940,6 +946,8 @@ completion-styles
   :type completion--styles-type
   :version "23.1")
 
+
+
 (defvar completion-category-defaults
   '((buffer (styles . (basic substring)))
     (unicode-name (styles . (basic substring)))
@@ -1288,8 +1296,12 @@ completion--in-region-1
     (let ((window minibuffer-scroll-window))
       (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 (and minibuffer-tab-go-completion
+                     (pos-visible-in-window-p (point-min) window))
+                ;; If all completions are visible move cursor there
+                (switch-to-completions)
+                ;; If end is in view, scroll up to the beginning.
+              (set-window-start window (point-min) nil))
           ;; Else scroll down one screen.
           (with-selected-window window
 	    (scroll-up)))
diff --git a/lisp/simple.el b/lisp/simple.el
index b45fb87887..c203efe16d 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -8359,6 +8359,12 @@ set-variable
 \f
 ;; Define the major mode for lists of completions.
 
+(defcustom completion-highlight-candidate t
+  "Non-nil means show help message in *Completions* buffer."
+  :type 'boolean
+  :version "28.1"
+  :group 'completion)
+
 (defvar completion-list-mode-map
   (let ((map (make-sparse-keymap)))
     (define-key map [mouse-2] 'choose-completion)
@@ -8372,6 +8378,12 @@ completion-list-mode-map
     (define-key map [backtab] 'previous-completion)
     (define-key map "q" 'quit-window)
     (define-key map "z" 'kill-current-buffer)
+
+    (define-key map (kbd "C-g") 'quit-window)
+    (define-key map (kbd "<up>") 'previous-line-completion)
+    (define-key map (kbd "C-p") 'previous-line-completion)
+    (define-key map (kbd "<down>") 'next-line-completion)
+    (define-key map (kbd "C-n") 'next-line-completion)
     map)
   "Local map for completion list buffers.")
 
@@ -8410,6 +8422,19 @@ completion-base-size
 If nil, Emacs determines which part of the tail end of the
 buffer's text is involved in completion by comparing the text
 directly.")
+
+(defvar completion-overlay nil
+  "Use a face to highlight completion candidate.")
+
+(defun move-completion-overlay ()
+  "Update completion overlay to highlight current candidate."
+  (let* ((obeg (point))
+         (oend (next-single-property-change obeg 'mouse-face nil (point-max))))
+    (unless (overlayp completion-overlay)
+      (setq completion-overlay (make-overlay 0 0))
+      (overlay-put completion-overlay 'face 'highlight))
+    (move-overlay completion-overlay obeg oend)))
+
 (make-obsolete-variable 'completion-base-size 'completion-base-position "23.2")
 
 (defun delete-completion-window ()
@@ -8428,7 +8453,7 @@ previous-completion
   (interactive "p")
   (next-completion (- n)))
 
-(defun next-completion (n)
+(defun next-completion (n &optional no-move-overlay)
   "Move to the next item in the completion list.
 With prefix argument N, move N items (negative N means move backward)."
   (interactive "p")
@@ -8454,7 +8479,25 @@ next-completion
 	;; Move to the start of that one.
 	(goto-char (previous-single-property-change
 		    (point) 'mouse-face nil beg))
-	(setq n (1+ n))))))
+	(setq n (1+ n)))))
+
+  (when (and completion-highlight-candidate
+             (not no-move-overlay))
+    (move-completion-overlay)))
+
+(defun next-line-completion (&optional arg try-vscroll)
+  "Go to completion candidate in line bellow current."
+  (interactive "^p\np")
+  (line-move arg t nil try-vscroll)
+  (next-completion 1 t)
+  (next-completion -1))
+
+(defun previous-line-completion (&optional arg try-vscroll)
+  "Go to completion candidate in line above current."
+  (interactive "^p\np")
+  (line-move (- arg) t nil try-vscroll)
+  (next-completion -1 t)
+  (next-completion 1))
 
 (defun choose-completion (&optional event)
   "Choose the completion at point.