Re: Gtk scrollbar: thumb too short

["Robert J. Chassell" <bob@rattlesnake.com>]

Miles Bader <miles@gnu.org> wrote

   ... I would _hate_ it if emacs insisted on preventing me from
   scrolling `past the end.'  [There are various reasons; sometimes I
   want to hide distracting text, sometimes I want to align text in
   adjacent windows a particular way, etc.]

I agree. We must able to scroll `past the end.'

The question is

  * How should you display scrolling past the end?

      - In Emacs 21.3 (current CVS):  by displaying the whole thumb,
        until last character of the buffer is in the top line of the
        window.  

        This means that in a short buffer, such as the initial
        *Messages* buffer in a plain Emacs 21.3 started with

            emacs -q --no-site-file --eval '(blink-cursor-mode 0)'

        the thumb does *not* show it is displaying `all' of the
        buffer, but shows the post-end-of-buffer empty lines too.

      - In Emacs 20.7:  by letting the scroll bar `sink' into the
        space below it, so it gets smaller and smaller, until the last
        character of the buffer is in the top line of the window.

I prefer the Emacs 20.7 way of doing it; that way, I don't think of
the thumb as telling me that the buffer is larger than it really is.

(My major use of the thumb and scroll bar is as a reporter; it tells
me where I am in the buffer and how large the buffer is.)

It is worth noting that a buffer is divided into three parts:

  * visible, accessible text

  * invisible text

  * inaccessible text from narrowing

and a window `contains' those three parts as well as 

  * post-eob empty lines

In addition to the question of how to display `scrolling past the
end', we have a question of

  * What fraction of a whole buffer should a thumb show?

      - the visible text portion of the whole buffer, regardless of
        narrowing, that is in the window displaying the buffer?

      - the visible, accessible portion of the whole buffer plus the
        invisible text that is `contained' within the window?

      - the portion of the visible region of the whole buffer that is
        displayed within the window?

I prefer that the thumb show the visible accessible portion of the
whole, that is to say, the part that is accessible either because it
is visible or because it is not hidden by narrowing.

This means that if you make some text invisible, for example by type
`C-c C-t' (hide-body) in outline mode, the thumb grows larger.

Likewise, if you make some text invisible and inaccessible by
narrowing to a smaller region, the thumb grows larger.

This is the way it is done in Emacs 20.7.

-- 
    Robert J. Chassell                         Rattlesnake Enterprises
    http://www.rattlesnake.com                  GnuPG Key ID: 004B4AC8
    http://www.teak.cc                             bob@rattlesnake.com