bug#18090: 24.4.50; `delete-selection-helper' logic changed for non-mouse region?

[Drew Adams <drew.adams@oracle.com>]

Prior to Emacs 23, the delsel.el code that handles a yank had this code:

;; Before a yank command, make sure we don't yank the
;; head of the kill-ring that really comes from the
;; currently active region we are going to delete.
;; That would make yank a no-op.
(when (and (string= (buffer-substring-no-properties (point) (mark))
                    (car kill-ring)))
  (current-kill 1))

That code dates from the creation of delsel.el.  In Emacs 23, these
two sexps were appended to the `and' conditions, which completely
changes the meaning/behavior (though the comment was not modified):

 (fboundp 'mouse-region-match)
 (mouse-region-match)

This changed the behavior so that the yanking point is now rotated only
when the mouse was used to set the region.  This makes no sense to me,
but perhaps I am missing something.  Does this make sense to you?
If it does make sense, then at least the comment should be updated to
reflect the current behavior.


---

BTW, I also think it would be better to use `while' instead of `when'
in the code:

(let ((tail  kill-ring))
  (while (and tail  (string= (buffer-substring-no-properties (point) (mark))
                             (car tail))
              (fboundp 'mouse-region-match) ; ????
              (mouse-region-match)) ; ????
    (current-kill 1)
    (setq tail  (cdr tail))))


In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
 of 2014-06-28 on ODIEONE
Bzr revision: 117431 rgm@gnu.org-20140628015517-eku6hj8mpgcvfnso
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''