Add a new prompter for meow-visit.

- Add user option `meow-vist-prompter`.

- Add `meow--prompt-buffer-highlight`, which highlights matches in the buffer
  similar to Isearch, and highlights all matches in the secondary selection
  while in Beacon Mode and point is in the secondary selection.

meow-command.el

@@ -1349,18 +1349,45 @@ Argument REVERSE if selection is reversed."
 The input will be pushed into `regexp-search-ring'.  So
 \\[meow-search] can be used for further searching with the same condition.
 
-A list of words and symbols in the current buffer will be provided for completion.
-To search for regexp instead, set `meow-visit-sanitize-completion' to nil.
-In that case, completions will be provided in regexp form, but also covering
+When `meow-prompter' is `completion' (the default), a list of
+words and symbols in the current buffer will be provided for
+completion.  To search for a regexp instead, set
+`meow-visit-sanitize-completion' to nil.  In that case,
+completions will be provided in regexp form, but also covering
 the words and symbols in the current buffer.
 
+When `meow-prompter' is `buffer-highlight', matches are
+highlighted in the current buffer from point until then end of
+the visible text.  When `meow-visit-sanitize-completion' is
+non-nil, only whole words and symbols are highlighted, and the
+input is treated literally.  When `meow-beacon-mode' is active
+and point is inside the secondary selection, matches back to the
+start or end of the selection are highlighted, depending on whether
+`meow-visit' is searching backward or forward.
+
 To search backward, use \\[negative-argument]."
   (interactive "P")
   (let* ((reverse arg)
          (pos (point))
-         (text (meow--prompt-symbol-and-words
-                (if arg "Visit backward: " "Visit: ")
-                (point-min) (point-max)))
+         (prompt (if reverse "Visit backward: " "Visit: "))
+         (text (pcase meow-visit-prompter
+                 ('buffer-highlight
+                  (apply #'meow--prompt-buffer-highlight
+                         prompt
+                         (let* ((ov-start (overlay-start mouse-secondary-overlay))
+                                (ov-end (overlay-end mouse-secondary-overlay))
+                                (use-sec (and (meow-beacon-mode-p)
+                                              (secondary-selection-exist-p)
+                                              (>= pos ov-start)
+                                              (< pos ov-end))))
+                           (if reverse
+                               (list (window-start (selected-window))
+                                     (if use-sec ov-end pos))
+                             (list (if use-sec ov-start pos)
+                                   (window-end (selected-window)))))))
+                 ((or 'completion _)
+                  (meow--prompt-symbol-and-words prompt
+                                                 (point-min) (point-max)))))
          (visit-point (meow--visit-point text reverse)))
     (if visit-point
         (let* ((m (match-data))

meow-util.el

@@ -290,6 +290,70 @@ Looks up the state in meow-replace-state-name-list"
               (regexp-quote selected))
         selected))))
 
+(defun meow--prompt-buffer-highlight (prompt beg end)
+  "PROMPT from the minibuffer while highlighting matches between BEG and END.
+
+When `meow-visit-sanitize-completion' is non-nil, matches are
+literal instead of regexps and only words and symbols are
+matched.
+
+Highlights are only visible in the selected window."
+  (let ((current-buffer (current-buffer))
+        (selected-window (selected-window))
+        (timer)
+        (overlays)
+        (prompter-minibuffer))
+    (cl-labels ((transform-text (txt &optional quote-regexp)
+                  (cond (meow-visit-sanitize-completion
+                         ;; To support Emacs 26.3, we need to use RX's `regexp'
+                         ;; form with `regexp-quote' instead of the `literal'
+                         ;; form, which was added in Emacs 27.
+                         (let ((qtd (regexp-quote txt)))
+                           (rx (or (seq symbol-start
+                                        (regexp qtd)
+                                        symbol-end)
+                                   (seq word-start
+                                        (regexp qtd)
+                                        word-end)))))
+                        (quote-regexp (regexp-quote txt))
+                        (t txt)))
+                (delete-overlays ()
+                  (mapc #'delete-overlay overlays)
+                  (setq overlays nil))
+                (highlight-matches ()
+                  ;; Before highlighting the minibuffer contents, we need to
+                  ;; check that we are still in the prompter's minibuffer, not
+                  ;; some other minibuffer.
+                  (when (or (not enable-recursive-minibuffers)
+                            (equal prompter-minibuffer (current-buffer)))
+                    (delete-overlays)
+                    (let ((regexp (transform-text (minibuffer-contents))))
+                      (unless (string-empty-p regexp)
+                        (save-excursion
+                          (with-current-buffer current-buffer
+                            (goto-char beg)
+                            (while (ignore-error invalid-regexp
+                                     ;; If the user is still typing the regexp it
+                                     ;; might not be valid.  In that case, we
+                                     ;; treat it as valid but not matching.
+                                     (re-search-forward regexp end t))
+                              (let ((ov (make-overlay (match-beginning 0)
+                                                      (match-end 0))))
+                                (overlay-put ov 'face 'lazy-highlight)
+                                ;; Same priority as Isearch lazy-highlight.
+                                (overlay-put ov 'priority 1000)
+                                (overlay-put ov 'window selected-window)
+                                (push ov overlays)))))))))
+                (make-hl-timer ()
+                  (run-with-idle-timer 0.01 'repeat #'highlight-matches)))
+      (unwind-protect
+          (minibuffer-with-setup-hook
+              (lambda () (setq timer (make-hl-timer)
+                               prompter-minibuffer (current-buffer)))
+            (transform-text (read-from-minibuffer prompt) t))
+        (cancel-timer timer)
+        (delete-overlays)))))
+
 (defun meow--on-window-state-change (&rest _args)
   "Update cursor style after switching window."
   (meow--update-cursor)

meow-var.el

@@ -153,8 +153,29 @@ This will affect how selection is displayed."
   :group 'meow
   :type '(repeat function))
 
+(defcustom meow-visit-prompter 'completion
+  "How `meow-visit' should prompt for a target.
+
+- `completion' (the default) means to present a lists of regexps
+  in the minibuffer, respecting the value of
+  `meow-visit-sanitize-completion'.
+
+- `buffer-highlight' means to highlight in the buffer the region
+  matching the text in the minibuffer, whether after or before
+  point.  If point is within the secondary selection and
+  `meow-beacon-mode' is active, then matches within the
+  secondary selection are also highlighted.  When
+  `meow-visit-sanitize-completion' is non-nil, this treats the
+  input literally and only matches whole words and symbols.
+
+Any other value is treated as `completion'."
+  :group 'meow
+  :type '(choice (const :tag "Show regexps in the minibuffer" completion)
+                 (const :tag "Highlight text in the buffer" buffer-highlight)))
+
 (defcustom meow-visit-collect-min-length 1
-  "Minimal length when collecting symbols for `meow-visit'."
+  "Minimal length when collecting symbols for `meow-visit' in the default prompter.
+See also `meow-visit-prompter'."
   :group 'meow
   :type 'integer)