bug#14017: Highlight prefix line numbers in occur

[Juri Linkov]

> Currently the `prefix-face' arg of `occur-engine' is unused.
> Its caller `occur-1' just sends nil to `occur-engine'.
> This is the reason why a bug in its usage in `occur-engine'
> remained undiscovered for a long time.
>
> To take it into use I propose to add a new face option
> `list-matching-lines-prefix-face' to accompany the existing
> `list-matching-lines-buffer-name-face' and `list-matching-lines-face'.

This is installed now.

Another problem I found with the line numbers in `occur' is that
the number of matches it reports in the header line is wrong.
If there are more than one match on a line, the total number
of matches is more than the total number of matching lines
currently displayed in the header line.  So I propose
to change the format of the occur header line from:

  2 matches for "is" in buffer: *scratch*

to:

  4 matches in 2 lines for "is" in buffer: *scratch*

I found that the exact number of matches (as opposed to
the number of matching lines) often is necessary to know beforehand
how many times it requires to type C-s to visit all matches
or how many times to type y/n to replace all matches in the buffer.

=== modified file 'lisp/replace.el'
--- lisp/replace.el     2013-02-25 20:57:44 +0000
+++ lisp/replace.el     2013-03-24 21:48:28 +0000
@@ -1347,16 +1347,18 @@ (defun occur-1 (regexp nlines bufs &opti
 (defun occur-engine (regexp buffers out-buf nlines case-fold
                            title-face prefix-face match-face keep-props)
   (with-current-buffer out-buf
-    (let ((globalcount 0)
+    (let ((global-lines 0)    ;; total count of matching lines
+         (global-matches 0)  ;; total count of matches
          (coding nil)
          (case-fold-search case-fold))
       ;; Map over all the buffers
       (dolist (buf buffers)
        (when (buffer-live-p buf)
-         (let ((matches 0)     ;; count of matched lines
-               (lines 1)       ;; line count
-               (prev-after-lines nil)  ;; context lines of prev match
-               (prev-lines nil)        ;; line number of prev match endpt
+         (let ((lines 0)               ;; count of matching lines
+               (matches 0)             ;; count of matches
+               (curr-line 1)           ;; line count
+               (prev-line nil)         ;; line number of prev match endpt
+               (prev-after-lines nil)  ;; context lines of prev match
                (matchbeg 0)
                (origpt nil)
                (begpt nil)
@@ -1376,8 +1378,9 @@ (defun occur-engine (regexp buffers out-
                (while (not (eobp))
                  (setq origpt (point))
                  (when (setq endpt (re-search-forward regexp nil t))
-                   (setq matches (1+ matches)) ;; increment match count
+                   (setq lines (1+ lines)) ;; increment matching lines count
                    (setq matchbeg (match-beginning 0))
                    ;; Get beginning of first match line and end of the last.
                    (save-excursion
@@ -1386,7 +1389,7 @@ (defun occur-engine (regexp buffers out-
                      (goto-char endpt)
                      (setq endpt (line-end-position)))
                    ;; Sum line numbers up to the first match line.
-                   (setq lines (+ lines (count-lines origpt begpt)))
+                   (setq curr-line (+ curr-line (count-lines origpt begpt)))
                    (setq marker (make-marker))
                    (set-marker marker matchbeg)
                    (setq curstring (occur-engine-line begpt endpt keep-props))
@@ -1395,6 +1398,7 @@ (defun occur-engine (regexp buffers out-
                          (start 0))
                      (while (and (< start len)
                                  (string-match regexp curstring start))
+                       (setq matches (1+ matches))
                        (add-text-properties
                         (match-beginning 0) (match-end 0)
                         (append
@@ -1408,7 +1412,7 @@ (defun occur-engine (regexp buffers out-
                    ;; Generate the string to insert for this match
                    (let* ((match-prefix
                            ;; Using 7 digits aligns tabs properly.
-                           (apply #'propertize (format "%7d:" lines)
+                           (apply #'propertize (format "%7d:" curr-line)
                                   (append
                                    (when prefix-face
                                      `(font-lock-face prefix-face))
@@ -1446,7 +1450,7 @@ (defun occur-engine (regexp buffers out-
                              ;; The complex multi-line display style.
                              (setq ret (occur-context-lines
                                         out-line nlines keep-props begpt endpt
-                                        lines prev-lines prev-after-lines))
+                                        curr-line prev-line prev-after-lines))
                              ;; Set first elem of the returned list to `data',
                              ;; and the second elem to `prev-after-lines'.
                              (setq prev-after-lines (nth 1 ret))
@@ -1458,28 +1462,30 @@ (defun occur-engine (regexp buffers out-
                  (if endpt
                      (progn
                        ;; Sum line numbers between first and last match lines.
-                       (setq lines (+ lines (count-lines begpt endpt)
-                                      ;; Add 1 for empty last match line since
-                                      ;; count-lines returns 1 line less.
-                                      (if (and (bolp) (eolp)) 1 0)))
+                       (setq curr-line (+ curr-line (count-lines begpt endpt)
+                                          ;; Add 1 for empty last match line 
since
+                                          ;; count-lines returns 1 line less.
+                                          (if (and (bolp) (eolp)) 1 0)))
                        ;; On to the next match...
                        (forward-line 1))
                    (goto-char (point-max)))
-                 (setq prev-lines (1- lines)))
+                 (setq prev-line (1- curr-line)))
                ;; Flush remaining context after-lines.
                (when prev-after-lines
                  (with-current-buffer out-buf
                    (insert (apply #'concat (occur-engine-add-prefix
                                             prev-after-lines)))))))
-           (when (not (zerop matches)) ;; is the count zero?
-             (setq globalcount (+ globalcount matches))
+           (when (not (zerop lines)) ;; is the count zero?
+             (setq global-lines (+ global-lines lines)
+                   global-matches (+ global-matches matches))
              (with-current-buffer out-buf
                (goto-char headerpt)
                (let ((beg (point))
                      end)
                  (insert (propertize
-                          (format "%d match%s%s in buffer: %s\n"
+                          (format "%d match%s in %d line%s%s in buffer: %s\n"
                                   matches (if (= matches 1) "" "es")
+                                  lines (if (= lines 1) "" "s")
                                   ;; Don't display regexp for multi-buffer.
                                   (if (> (length buffers) 1)
                                       "" (format " for \"%s\""
@@ -1494,12 +1500,13 @@ (defun occur-engine (regexp buffers out-
                                        `(occur-title ,buf))))
                (goto-char (point-min)))))))
       ;; Display total match count and regexp for multi-buffer.
-      (when (and (not (zerop globalcount)) (> (length buffers) 1))
+      (when (and (not (zerop global-lines)) (> (length buffers) 1))
        (goto-char (point-min))
        (let ((beg (point))
              end)
-         (insert (format "%d match%s total for \"%s\":\n"
-                         globalcount (if (= globalcount 1) "" "es")
+         (insert (format "%d match%s in %d line%s total for \"%s\":\n"
+                         global-matches (if (= global-matches 1) "" "es")
+                         global-lines (if (= global-lines 1) "" "s")
                          (query-replace-descr regexp)))
          (setq end (point))
          (add-text-properties beg end (when title-face
@@ -1510,8 +1517,8 @@ (defun occur-engine (regexp buffers out-
          ;; that locally binds it.  Let's use it also for the output
          ;; buffer.
          (set-buffer-file-coding-system coding))
-      ;; Return the number of matches
-      globalcount)))
+      ;; Return the number of matching lines
+      global-lines)))
 
 (defun occur-engine-line (beg end &optional keep-props)
   (if (and keep-props (if (boundp 'jit-lock-mode) jit-lock-mode)
@@ -1551,13 +1558,13 @@ (defun occur-accumulate-lines (count &op
 ;; Generate context display for occur.
 ;; OUT-LINE is the line where the match is.
 ;; NLINES and KEEP-PROPS are args to occur-engine.
-;; LINES is line count of the current match,
-;; PREV-LINES is line count of the previous match,
+;; CURR-LINE is line count of the current match,
+;; PREV-LINE is line count of the previous match,
 ;; PREV-AFTER-LINES is a list of after-context lines of the previous match.
 ;; Generate a list of lines, add prefixes to all but OUT-LINE,
 ;; then concatenate them all together.
 (defun occur-context-lines (out-line nlines keep-props begpt endpt
-                                    lines prev-lines prev-after-lines)
+                                    curr-line prev-line prev-after-lines)
   ;; Find after- and before-context lines of the current match.
   (let ((before-lines
         (nreverse (cdr (occur-accumulate-lines
@@ -1572,22 +1579,22 @@ (defun occur-context-lines (out-line nli
 
     (when prev-after-lines
       ;; Don't overlap prev after-lines with current before-lines.
-      (if (>= (+ prev-lines (length prev-after-lines))
-             (- lines      (length before-lines)))
+      (if (>= (+ prev-line (length prev-after-lines))
+             (- curr-line      (length before-lines)))
          (setq prev-after-lines
                (butlast prev-after-lines
                         (- (length prev-after-lines)
-                           (- lines prev-lines (length before-lines) 1))))
+                           (- curr-line prev-line (length before-lines) 1))))
        ;; Separate non-overlapping context lines with a dashed line.
        (setq separator "-------\n")))
 
-    (when prev-lines
+    (when prev-line
       ;; Don't overlap current before-lines with previous match line.
-      (if (<= (- lines (length before-lines))
-             prev-lines)
+      (if (<= (- curr-line (length before-lines))
+             prev-line)
          (setq before-lines
                (nthcdr (- (length before-lines)
-                          (- lines prev-lines 1))
+                          (- curr-line prev-line 1))
                        before-lines))
        ;; Separate non-overlapping before-context lines.
        (unless (> nlines 0)