GNU bug report logs - #23347
25.0.92; Follow mode scrolling broken -- scrolls only one page

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From: Anders Lindgren <andlind <at> gmail.com>
To: Alan Mackenzie <acm <at> muc.de>
Cc: 23347 <at> debbugs.gnu.org
Subject: bug#23347: 25.0.92; Follow mode scrolling broken -- scrolls only one page
Date: Sun, 24 Apr 2016 17:37:57 +0200

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Hi!


> > The normal `scroll-up-command' and `scroll-down-command' (typically bound
> > to C-v and M-v) can scroll a page at a time, there is no need for a
> Follow
> > mode-specific command for that, as the normal Follow mode machinery can
> > reposition the other windows. (The only difference is that when using C-v
> > the original window is still selected, whereas with the new
> > follow-scroll-up command the windows where the original point ends up is
> > selected.)
>
> Indeed.  This is a difference important enough to have a command in
> follow.el which keeps point at the same buffer position it started with.
>

Agreed. All three scroll commands (non-follow-mode scroll, scroll one page,
and scroll N pages) are useful.

> A cleaner solution would be to define two sets of functions, e.g.
> > follow-scroll-up-one-page.
>
> OK.  I'm happy enought with that.
>
> I'm not sure that's a good name, though - the "page" bit could easily
> get confused with the region in a buffer between two ^L characters.
>
> Maybe follow-scroll-up-window would be better.  What do you think?
>

Yes, I agree, `page' isn't a good choice.

What about `follow-scroll-up-keep-point'? That way it would be clear what
the difference is between it and the normal scroll command.

If I would have designed Follow mode today, I probably would have used your
name, `follow-scroll-up-window', and named the N-page scroll
`follow-scroll-up-window-group'.



> > Many users might want to use both kind of scrolling (I use both C-v
> > and C-c . C-v several time every day, depending on how I would like to
> > scroll the display). With two sets of functions it's easier to do
> > this. (Also, it's easier to write documentation for a function
> > designed to do one thing.)
>
> For me, C-c . C-v is too tedious to type, so I've just bound <PageUp>
> and <PageDown> to `follow-scroll-down/up'.  I use them many times per
> day.
>

I've remapped them to C-c C-v and C-c v, that way I can scroll a window
down a single page using C-v and the entire display using C-c C-v. Of
course, this isn't in a part of a keymap available to minor modes, so it's
nothing we can make official.


Another possibility would be to use a C-u prefix argument to indicate N
> windows as opposed to 1.  No, I don't think that's a good idea, either.
>

No, too cumbersome.


Anyway, here is what I think we can agree on:
> 1. `follow-scroll-up/down' should scroll by N windows.
> 2. There need to be commands in follow.el that scroll by 1 window as is
>   done by the current `follow-scroll-up/down'.  You have suggested the
>   name `follow-scroll-up/down-one-page'.  I have countered with
>   `follow-scroll-up/down-window'.
>
> If we can agree, I'm willing to amend follow.el.  I think it's probably
> too late for this fix to make it into Emacs 25.1, though.
>

Well, give it a try. Feel free to pick a suitable name. If we come up with
a clean solution quickly John might accept it.

    -- Anders

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