bug#29321: Isearch hit count

[Juri Linkov]

> Could we prevent the "0/0" count from showing when searching for an
> incomplete regexp?  For example, typing characters after C-M-s [
> results in the isearch prompt shifting when the "0/0" count is
> displayed lazily after each keypress.
>
> Also, the count is shown in the prompt even for "M-e".  For example,
> C-s buf M-e shows "1/2 I-search:" as the (static) prompt, which is not
> necessary (and it may be outdated as soon as the user changes the text
> in the minibuffer).

I agree on both accounts, and fixed this in a new patch that also
includes two new customizable variables lazy-count-prefix-format and
lazy-count-suffix-format:

diff --git a/lisp/isearch.el b/lisp/isearch.el
index 42b3aa42ba..5f75e90387 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -316,6 +316,29 @@ isearch-lazy-highlight
   :group 'lazy-highlight
   :group 'isearch)
 
+(defcustom isearch-lazy-count nil
+  "Show match number in the Isearch prompt.
+When both this option and `isearch-lazy-highlight' are non-nil,
+show the current match number and the total number of matches
+in the buffer (or its restriction)."
+  :type 'boolean
+  :group 'isearch
+  :version "27.1")
+
+(defcustom lazy-count-prefix-format "%s/%s "
+  "Format of the current/total number of matches for message prefix."
+  :type '(choice (const :tag "No prefix" nil)
+                 (string :tag "Prefix format string" "%s/%s "))
+  :group 'isearch
+  :version "27.1")
+
+(defcustom lazy-count-suffix-format nil
+  "Format of the current/total number of matches for message suffix."
+  :type '(choice (const :tag "No suffix" nil)
+                 (string :tag "Suffix format string" " [%s of %s]"))
+  :group 'isearch
+  :version "27.1")
+
 ;;; Lazy highlight customization.
 
 (defgroup lazy-highlight nil
@@ -2794,7 +2821,8 @@ isearch-message-prefix
                        (concat " [" current-input-method-title "]: "))
                     ": ")
                   )))
-    (propertize (concat (upcase (substring m 0 1)) (substring m 1))
+    (propertize (concat (isearch-lazy-count-format)
+                        (upcase (substring m 0 1)) (substring m 1))
                'face 'minibuffer-prompt)))
 
 (defun isearch-message-suffix (&optional c-q-hack)
@@ -2802,9 +2830,33 @@ isearch-message-suffix
                      (if isearch-error
                          (concat " [" isearch-error "]")
                        "")
+                      (isearch-lazy-count-format 'suffix)
                      (or isearch-message-suffix-add ""))
               'face 'minibuffer-prompt))
 
+(defun isearch-lazy-count-format (&optional suffix-p)
+  "Format the current match number and the total number of matches.
+When SUFFIX-P is non-nil, the returned string is indended for
+isearch-message-suffix.  Otherwise, for isearch-message-prefix."
+  (let ((format-string (if suffix-p
+                           lazy-count-suffix-format
+                         lazy-count-prefix-format)))
+    (if (and format-string
+             isearch-lazy-count
+             isearch-lazy-count-current
+             (not isearch-error)
+             (not isearch-suspended))
+        (format format-string
+                (if isearch-forward
+                    isearch-lazy-count-current
+                  (if (eq isearch-lazy-count-current 0)
+                      0
+                    (- isearch-lazy-count-total
+                       isearch-lazy-count-current
+                       -1)))
+                (or isearch-lazy-count-total "?"))
+      "")))
+
 
 ;; Searching
 
@@ -3202,6 +3254,8 @@ isearch-lazy-highlight-window
 (defvar isearch-lazy-highlight-window-group nil)
 (defvar isearch-lazy-highlight-window-start nil)
 (defvar isearch-lazy-highlight-window-end nil)
+(defvar isearch-lazy-highlight-window-start-changed nil)
+(defvar isearch-lazy-highlight-window-end-changed nil)
 (defvar isearch-lazy-highlight-point-min nil)
 (defvar isearch-lazy-highlight-point-max nil)
 (defvar isearch-lazy-highlight-buffer nil)
@@ -3214,6 +3268,9 @@ 'isearch-lazy-highlight-word
 (defvar isearch-lazy-highlight-regexp-function nil)
 (defvar isearch-lazy-highlight-forward nil)
 (defvar isearch-lazy-highlight-error nil)
+(defvar isearch-lazy-count-current nil)
+(defvar isearch-lazy-count-total nil)
+(defvar isearch-lazy-count-hash (make-hash-table))
 
 (defun lazy-highlight-cleanup (&optional force procrastinate)
   "Stop lazy highlighting and remove extra highlighting from current buffer.
@@ -3258,18 +3315,36 @@ isearch-lazy-highlight-new-loop
                 ;; In case we are recovering from an error.
                 (not (equal isearch-error
                             isearch-lazy-highlight-error))
-                (not (if lazy-highlight-buffer
-                         (= (point-min)
-                            isearch-lazy-highlight-point-min)
-                       (= (window-group-start)
-                          isearch-lazy-highlight-window-start)))
-                (not (if lazy-highlight-buffer
-                         (= (point-max)
-                            isearch-lazy-highlight-point-max)
-                       (= (window-group-end) ; Window may have been 
split/joined.
-                          isearch-lazy-highlight-window-end)))))
+                (if lazy-highlight-buffer
+                    (not (= (point-min)
+                            isearch-lazy-highlight-point-min))
+                  (setq isearch-lazy-highlight-window-start-changed
+                         (not (= (window-group-start)
+                                isearch-lazy-highlight-window-start))))
+                (if lazy-highlight-buffer
+                    (not (= (point-max)
+                            isearch-lazy-highlight-point-max))
+                  (setq isearch-lazy-highlight-window-end-changed
+                         (not (= (window-group-end) ; Window may have been 
split/joined.
+                                isearch-lazy-highlight-window-end))))))
     ;; something important did indeed change
     (lazy-highlight-cleanup t (not (equal isearch-string ""))) ;stop old timer
+    (when (and isearch-lazy-count isearch-mode)
+      (when (or (equal isearch-string "")
+                (and (not isearch-lazy-highlight-window-start-changed)
+                     (not isearch-lazy-highlight-window-end-changed))
+                (not (= (point-min)
+                       isearch-lazy-highlight-point-min))
+                (not (= (point-max)
+                       isearch-lazy-highlight-point-max)))
+        ;; Reset old counter before going to count new numbers
+        (clrhash isearch-lazy-count-hash)
+        (setq isearch-lazy-count-current nil
+              isearch-lazy-count-total nil)
+        (when (null isearch-message-function)
+          (isearch-message nil t))))
+    (setq isearch-lazy-highlight-window-start-changed nil)
+    (setq isearch-lazy-highlight-window-end-changed nil)
     (setq isearch-lazy-highlight-error isearch-error)
     ;; It used to check for `(not isearch-error)' here, but actually
     ;; lazy-highlighting might find matches to highlight even when
@@ -3313,7 +3388,14 @@ isearch-lazy-highlight-new-loop
     (unless (equal isearch-string "")
       (setq isearch-lazy-highlight-timer
             (run-with-idle-timer lazy-highlight-initial-delay nil
-                                 'isearch-lazy-highlight-start)))))
+                                 'isearch-lazy-highlight-start))))
+  (when (and isearch-lazy-count isearch-mode (null isearch-message-function))
+    ;; Update isearch-lazy-count-current only when it was already set
+    ;; at the end of isearch-lazy-highlight-buffer-update
+    (when isearch-lazy-count-current
+      (setq isearch-lazy-count-current
+            (or (gethash (point) isearch-lazy-count-hash) 0))
+      (isearch-message nil t))))
 
 (defun isearch-lazy-highlight-search (string bound)
   "Search ahead for the next or previous match, for lazy highlighting.
@@ -3434,7 +3516,8 @@ isearch-lazy-highlight-update
                        (goto-char (min (or isearch-lazy-highlight-end-limit 
(point-max))
                                        window-end)))))))
            (if nomore
-               (when isearch-lazy-highlight-buffer
+               (when (or isearch-lazy-highlight-buffer
+                          (and isearch-lazy-count (null 
isearch-lazy-count-current)))
                  (if isearch-lazy-highlight-forward
                      (setq isearch-lazy-highlight-end (point-min))
                    (setq isearch-lazy-highlight-start (point-max)))
@@ -3448,7 +3531,8 @@ isearch-lazy-highlight-buffer-update
   "Update highlighting of other matches in the full buffer."
   (let ((max lazy-highlight-buffer-max-at-a-time)
         (looping t)
-        nomore window-start window-end)
+        nomore window-start window-end
+        (opoint (point)))
     (with-local-quit
       (save-selected-window
        (if (and (window-live-p isearch-lazy-highlight-window)
@@ -3483,8 +3567,14 @@ isearch-lazy-highlight-buffer-update
                            (if (= mb (point-min))
                                (setq found nil)
                              (forward-char -1)))
+                       (when isearch-lazy-count
+                         (setq isearch-lazy-count-total (1+ (or 
isearch-lazy-count-total 0)))
+                          (puthash (if isearch-lazy-highlight-forward me mb)
+                                   isearch-lazy-count-total
+                                   isearch-lazy-count-hash))
                        ;; Already highlighted by isearch-lazy-highlight-update
-                       (unless (and (>= mb window-start) (<= me window-end))
+                        (unless (or (not isearch-lazy-highlight-buffer)
+                                    (and (>= mb window-start) (<= me 
window-end)))
                          ;; non-zero-length match
                          (isearch-lazy-highlight-match mb me)))
                      ;; Remember the current position of point for
@@ -3498,7 +3588,13 @@ isearch-lazy-highlight-buffer-update
                (if (not found)
                    (setq looping nil
                          nomore  t))))
-           (unless nomore
+           (if nomore
+               (when (and isearch-lazy-count isearch-mode (null 
isearch-message-function))
+                  (unless isearch-lazy-count-total
+                    (setq isearch-lazy-count-total 0))
+                  (setq isearch-lazy-count-current
+                        (or (gethash opoint isearch-lazy-count-hash) 0))
+                  (isearch-message nil t))
              (setq isearch-lazy-highlight-timer
                    (run-at-time lazy-highlight-interval nil
                                 'isearch-lazy-highlight-buffer-update)))))))))