bug#68215: Bug in what-page

[Lars Brinkhoff <lars.brinkhoff@gmail.com>]

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Eli Zaretskii <eliz@gnu.org> wrote:
> It should be a simple matter to countermand this special-casing in
> what-page, while still using count-lines.  Or am I missing something?

That's probably better.  I'm attaching an updated patch which uses
count-lines instead.  It countermands the special case by checking
(bolp) and then doing the opposite adjustment.

However, there's one more case to consider: when point starts out
right after a page delimiter (i.e. the very first positon on a page),
the page--what-page while loop will leave the final point there too,
and then count-lines will return 0.  The line number should be 1, so
an adjustment is needed there too.

The updated test is the same as the previous round, and they still
pass with the new patch.

> > +  "Return a list of the page number of point, and the line number
> > +within that page."
>
> Our convention is to have the first line of a doc string be a single
> complete sentence.

Fixed by moving info to a second line, or rephrasing to one line.

[-- Attachment #2: what-line-2.patch --]
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commit 746013e179735673b2ad535ea46d54bae3f38d50
Author: Lars Brinkhoff <lars@nocrew.org>
Date:   Tue Jan 2 09:06:13 2024 +0100

    Fix what-page.

diff --git a/lisp/textmodes/page.el b/lisp/textmodes/page.el
index e8621ee0383..1c7561d71c6 100644
--- a/lisp/textmodes/page.el
+++ b/lisp/textmodes/page.el
@@ -159,21 +159,23 @@ count-lines-page
              total before after)))
 
 (defun page--what-page ()
-  "Return a list of the page and line number of point."
+  "Return a list of the page and line number of point.
+The line number is relative to the start of the page."
   (save-restriction
     (widen)
     (save-excursion
       (let ((count 1)
+            (adjust (if (or (bolp) (looking-back page-delimiter)) 1 0))
             (opoint (point)))
         (goto-char (point-min))
         (while (re-search-forward page-delimiter opoint t)
           (when (= (match-beginning 0) (match-end 0))
             (forward-char))
           (setq count (1+ count)))
-        (list count (line-number-at-pos opoint))))))
+        (list count (+ adjust (count-lines (point) opoint)))))))
 
 (defun what-page ()
-  "Print page and line number of point."
+  "Display the page number, and the line number within that page."
   (interactive)
   (apply #'message (cons "Page %d, line %d" (page--what-page))))
 
diff --git a/test/lisp/textmodes/page-tests.el b/test/lisp/textmodes/page-tests.el
index f3a2c5fbe00..617b59a54fb 100644
--- a/test/lisp/textmodes/page-tests.el
+++ b/test/lisp/textmodes/page-tests.el
@@ -106,10 +106,14 @@ page-tests-what-page
     (insert "foo\n\f\nbar\n\f\nbaz")
     (goto-char (point-min))
     (should (equal (page--what-page) '(1 1)))
+    (forward-char)
+    (should (equal (page--what-page) '(1 1)))
     (forward-page)
+    (should (equal (page--what-page) '(2 1)))
+    (next-line)
     (should (equal (page--what-page) '(2 2)))
     (forward-page)
-    (should (equal (page--what-page) '(3 4)))))
+    (should (equal (page--what-page) '(3 1)))))
 
 
 ;;; page-tests.el ends here