2 files changed, 140 insertions, 3 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 33a2b3fd07a..efd03313f17 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1591,6 +1591,26 @@ width of the 'speedbar-window' when it is closed and then restored.
 ---
 *** 'speedbar-easymenu-definition-trailer' is now a function.
 
+** Icomplete
+
+*** New user options for 'icomplete-vertical-mode'.
+New user options have been added to enhance 'icomplete-vertical-mode':
+- 'icomplete-vertical-in-buffer-adjust-list' aligns in-buffer
+  completion to the original cursor column.
+- 'icomplete-vertical-render-prefix-indicator' adds a prefix indicator
+  to completion candidates.
+- 'icomplete-vertical-selected-prefix-indicator' specifies the prefix
+  string for the selected candidate.
+- 'icomplete-vertical-unselected-prefix-indicator' specifies the prefix
+  string for unselected candidates.
+
+*** New faces for 'icomplete-vertical-mode'.
+New faces have been added to 'icomplete-vertical-mode':
+- 'icomplete-vertical-selected-prefix-indicator-face' controls the
+  appearance of the selected candidate prefix.
+- 'icomplete-vertical-unselected-prefix-indicator-face' controls the
+  appearance of unselected candidate prefixes.
+
 ** Miscellaneous
 
 ---
diff --git a/lisp/icomplete.el b/lisp/icomplete.el
index c58bffbb36b..d0cc5674ba7 100644
--- a/lisp/icomplete.el
+++ b/lisp/icomplete.el
@@ -115,6 +115,18 @@ Otherwise this should be a list of the completion tables (e.g.,
   "Face used by `icomplete-vertical-mode' for the section title."
   :version "28.1")
 
+(defface icomplete-vertical-selected-prefix-indicator-face
+  '((t :inherit font-lock-keyword-face :weight bold :foreground "slate blue"))
+  "Face used by `icomplete-vertical-selected-prefix-indicator'."
+  :group 'icomplete
+  :version "31.1")
+
+(defface icomplete-vertical-unselected-prefix-indicator-face
+  '((t :inherit font-lock-keyword-face :weight normal :foreground "gray"))
+  "Face used by `icomplete-vertical-unselected-prefix-indicator'."
+  :group 'icomplete
+  :version "31.1")
+
 ;;;_* User Customization variables
 (defcustom icomplete-prospects-height 2
   ;; We used to compute how many lines 100 characters would take in
@@ -166,6 +178,50 @@ will constrain Emacs to a maximum minibuffer height of 3 lines when
 icompletion is occurring."
   :type 'hook)
 
+(defcustom icomplete-vertical-in-buffer-adjust-list nil
+  "Control whether in-buffer completion should align the cursor position.
+If this is t and `icomplete-in-buffer' is t, and `icomplete-vertical-mode'
+is activated, the in-buffer vertical completions are shown aligned to the
+cursor position when the completion started, not on the first column, as
+the default behavior."
+  :type 'boolean
+  :group 'icomplete
+  :version "31.1")
+
+(defcustom icomplete-vertical-render-prefix-indicator nil
+  "Control whether an indicator is added as a prefix to each candidate.
+If this is t and `icomplete-vertical-mode' is activated, an indicator,
+controlled by `icomplete-vertical-selected-prefix-indicator' is shown
+as a prefix to the current under selection candidate, while the
+remaining of the candidates will receive the indicator controlled
+by `icomplete-vertical-unselected-prefix-indicator'."
+  :type 'boolean
+  :group 'icomplete
+  :version "31.1")
+
+(defcustom icomplete-vertical-selected-prefix-indicator
+  (if (char-displayable-p ?») "» " "> ")
+  "Prefix string used to mark the selected completion candidate.
+If `icomplete-vertical-render-prefix-indicator' is t, this string
+is used as a prefix of the currently selected entry in the list.
+It can be further customized by the face
+`icomplete-vertical-selected-prefix-indicator-face'.
+
+By default, this is set to \"» \" if the character is displayable,
+otherwise, it falls back to \"> \"."
+  :type 'string
+  :group 'icomplete
+  :version "31.1")
+
+(defcustom icomplete-vertical-unselected-prefix-indicator "  "
+  "Prefix string used on the unselected completion candidates.
+If `icomplete-vertical-render-prefix-indicator' is t, the string
+defined here is used as a prefix for all unselected entries in the list.
+list.  It can be further customized by the face
+`icomplete-vertical-unselected-prefix-indicator-face'."
+  :type 'string
+  :group 'icomplete
+  :version "31.1")
 
 ;;;_* Initialization
 
@@ -828,6 +884,58 @@ by `group-function''s second \"transformation\" protocol."
                  else collect (list tr prefix suffix ))
       annotated)))
 
+(defun icomplete-vertical--adjust-lines-for-column (lines buffer data)
+  "Adjust the LINES to align with the column in BUFFER based on DATA."
+  (if icomplete-vertical-in-buffer-adjust-list
+      (let* ((column (current-column))
+             (prefix-indicator-width
+              (if icomplete-vertical-render-prefix-indicator
+                  (max (length icomplete-vertical-selected-prefix-indicator)
+                       (length icomplete-vertical-unselected-prefix-indicator))
+                0))
+             (wrapped-line (with-current-buffer buffer
+                             (save-excursion
+                               (goto-char (car data))
+                               (beginning-of-line)
+                               (count-screen-lines (point) (car data)))))
+             (window-width (+ (window-hscroll) (window-body-width)))
+             (longest-line-width (apply #'max (mapcar #'length lines)))
+             (spaces-to-add
+              (if (> wrapped-line 1)
+                  (- column (* (- wrapped-line 1) (- window-width 5)))
+                column))
+             (spaces-to-add-avoiding-scrolling
+              (if (>= (+ spaces-to-add longest-line-width prefix-indicator-width) window-width)
+                  (- spaces-to-add longest-line-width)
+                spaces-to-add)))
+
+        (mapcar (lambda (line)
+                  (concat (make-string spaces-to-add-avoiding-scrolling ?\s) line))
+                lines))
+    lines))
+
+(defun icomplete-vertical--ensure-visible-lines-inside-buffer ()
+  "Ensure the completion list is visible in regular buffers only.
+Scrolls the screen to be at least `icomplete-prospects-height' real lines
+away from the bottom.  Counts wrapped lines as real lines."
+  (unless (minibufferp)
+    (let* ((window-height (window-body-height))
+           (current-line (count-screen-lines (window-start) (point)))
+           (lines-to-bottom (- window-height current-line)))
+      (when (< lines-to-bottom icomplete-prospects-height)
+        (scroll-up (- icomplete-prospects-height lines-to-bottom))))))
+
+(defun icomplete-vertical--add-indicator-to-selected (comp)
+  "Add indicators to the selected/unselected COMP completions."
+  (if (and icomplete-vertical-render-prefix-indicator
+           (get-text-property 0 'icomplete-selected comp))
+      (concat (propertize icomplete-vertical-selected-prefix-indicator
+                          'face 'icomplete-vertical-selected-prefix-indicator-face)
+              comp)
+    (concat (propertize icomplete-vertical-unselected-prefix-indicator
+                        'face 'icomplete-vertical-unselected-prefix-indicator-face)
+            comp)))
+
 (cl-defun icomplete--render-vertical
     (comps md &aux scroll-above scroll-below
            (total-space ; number of mini-window lines available
@@ -843,12 +951,17 @@ by `group-function''s second \"transformation\" protocol."
   ;; - both nil, there is no manual scroll;
   ;; - both non-nil, there is a healthy manual scroll that doesn't need
   ;;   to be readjusted (user just moved around the minibuffer, for
-  ;;   example)l
+  ;;   example);
   ;; - non-nil and nil, respectively, a refiltering took place and we
   ;;   may need to readjust them to the new filtered `comps'.
   (when (and icomplete-scroll
+             (not icomplete--scrolled-completions)
+             (not icomplete--scrolled-past))
+    (icomplete-vertical--ensure-visible-lines-inside-buffer))
+  (when (and icomplete-scroll
              icomplete--scrolled-completions
              (null icomplete--scrolled-past))
+    (icomplete-vertical--ensure-visible-lines-inside-buffer)
     (cl-loop with preds
              for (comp . rest) on comps
              when (equal comp (car icomplete--scrolled-completions))
@@ -900,6 +1013,7 @@ by `group-function''s second \"transformation\" protocol."
     ;; of lines to render
     (cl-loop
      for (comp prefix suffix section) in tuples
+     do (setq comp (icomplete-vertical--add-indicator-to-selected comp))
      when section
      collect (propertize section 'face 'icomplete-section) into lines-aux
      and count 1 into nsections-aux
@@ -907,9 +1021,9 @@ by `group-function''s second \"transformation\" protocol."
      do (add-face-text-property 0 (length comp)
                                 'icomplete-selected-match 'append comp)
      collect (concat prefix
-                     (make-string (- max-prefix-len (length prefix)) ? )
+                     (make-string (max 0 (- max-prefix-len (length prefix))) ? )
                      (completion-lazy-hilit comp)
-                     (make-string (- max-comp-len (length comp)) ? )
+                     (make-string (max 0 (- max-comp-len (length comp))) ? )
                      suffix)
      into lines-aux
      finally (setq lines lines-aux
@@ -924,6 +1038,9 @@ by `group-function''s second \"transformation\" protocol."
                  ((> (length scroll-above) (length scroll-below)) nsections)
                  (t (min (ceiling nsections 2) (length scroll-above))))
            lines))
+    (when icomplete--in-region-buffer
+      (setq lines (icomplete-vertical--adjust-lines-for-column
+                   lines icomplete--in-region-buffer completion-in-region--data)))
     ;; At long last, render final string return value.  This may still
     ;; kick out lines at the end.
     (concat " \n"