bug#13690: 24.3.50; scroll-conservatively and Info-up

[Stephen Berman]

On Thu, 14 Feb 2013 07:12:38 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <stephen.berman@gmx.net>
>> Cc: 13690@debbugs.gnu.org
>> Date: Thu, 14 Feb 2013 00:18:30 +0100
>> 
>> >   . scroll-conservatively being non-nil
>> 
>> I think you mean non-zero, since only integer values are admissible.
>> But when scroll-conservatively is zero, recentering happens anyway, so I
>> don't see the point of adding this condition.  Or is there a problem is
>> if recentering happens twice (once directly from the display engine and
>> once by explicitly calling recenter)?  I don't notice any problem.
>
> Why recenter twice?  It's a waste of cycles.

Ok.

>> >   . perhaps also scroll-margin being zero, because otherwise you get
>> >     several lines of context before point
>> 
>> I tested scroll-margin and found no difference in the behavior of Info-up
>> whether it is zero or non-zero; do you see something different?
>
> Do you have the latest trunk?  If so, you should see a difference:
> when scroll-margin is N, typing 'u' puts the line with cursor N+1
> lines from the top.

Ah, I just updated and now see it (my previous build was a couple of
days too old).  However, I would prefer for Info-up to recenter even if
scroll-margin is non-zero.  When using C-p or C-n, I can well imagine
wanting the display to start scrolling before point reaches the top or
bottom of the window, i.e., I might want to set scroll-margin to a
non-zero value.  But when I type `u' in Info, I really want to see as
much of the superior node as possible, not just one or two lines above
the target line.  If scroll-margin obeyed SCROLL_LIMIT like
scroll-conservatively does (or perhaps a different limit just for
scroll-margin), this would allow more flexibility.  But in default of
that, and not wanting to complicate things with another user option (at
least until someone screams bloody murder), I would rather omit the
scroll-margin check for now.

2014-02-13  Stephen Berman  <stephen.berman@gmx.net>

        * info.el (Info-up): If scroll-conservatively is non-zero and
        less than 101, display as much of the superior node above the
        target line as possible.  (Bug#13690)

=== modified file 'lisp/info.el'
*** lisp/info.el        2013-02-14 09:15:55 +0000
--- lisp/info.el        2013-02-14 11:27:50 +0000
***************
*** 2246,2252 ****
                nil t))
          (progn (beginning-of-line) (if (looking-at "^\\* ") (forward-char 2)))
        (goto-char p)
!       (Info-restore-point Info-history)))))
  
  (defun Info-history-back ()
    "Go back in the history to the last node visited."
--- 2246,2257 ----
                nil t))
          (progn (beginning-of-line) (if (looking-at "^\\* ") (forward-char 2)))
        (goto-char p)
!       (Info-restore-point Info-history))))
!   ;; If scroll-conservatively is non-zerop and less than 101, display
!   ;; as much of the superior node above the target line as possible
!   ;; (bug#13690).
!   (when (and (> scroll-conservatively 0) (< scroll-conservatively 101))
!     (recenter)))
  
  (defun Info-history-back ()
    "Go back in the history to the last node visited."