Re: wish list: thread-gathering sort options

[Ken Raeburn <raeburn@raeburn.org>]

I wrote:
> Truxton Fulton <trux@truxton.com> writes:
>> I found a work-around that does the trick for me.  The thread
>> gathering process gathers lower threads up to the higher thread.
>> If this could be reversed (since the thread sorting order is also
>> reversed), that would solve the problem.
> That gets the groups of gathered threads into the proper order, but
> wouldn't it put the thread with the latest messages first within each
> group?  I think I'd want the threads within each gathered group to be
> sorted by most-recent number or date too.

Looks like I was wrong.  I'm getting the threads within the gathered
groups in the correct order.  Yay!

Though I'm a little confused why it's working.  Probably I've just got
the wrong mental picture for how the gathering is working.  But that's
much less important than the fact that it's working.  :-)

Looks like I've got a new thread gathering function to use, for now:

    (defun kr-gnus-gather-threads-by-subject-reversed (threads)
      (reverse (gnus-gather-threads-by-subject (reverse threads))))

So, is it safe to use "nreverse" instead of "reverse" in
either or both of these cases?

And assuming this is in fact the right way to implement this reversal,
would it make sense to create yet another customization variable to
control this behavior, something like this (untested):

(defcustom gnus-summary-place-gathered-threads-last
  nil
  "*If non-nil, causes gathered threads to be retained in the original
position of the last of the threads gathered.  If nil, the gathered
threads are placed in the position of the first thread gathered."
  :group 'gnus-thread
  :type 'boolean)

...
       (if gnus-show-threads
           (if gnus-summary-place-gathered-threads-last
              (gnus-sort-gathered-threads
               (reverse
                (funcall gnus-summary-thread-gathering-function
                         (reverse
                          (gnus-sort-threads
                           (gnus-cut-threads (gnus-make-threads)))))))
             (gnus-sort-gathered-threads
              (funcall gnus-summary-thread-gathering-function
                       (gnus-sort-threads
                        (gnus-cut-threads (gnus-make-threads))))))
	 ;; Unthreaded display.
	 (gnus-sort-articles gnus-newsgroup-headers))))

Or maybe gnus-summary-thread-gathering-function should be allowed to
have an alternative form like '(reverse . some-function)?

Ken