Re: Is there any particular reason `scroll-other-window' is written in C and not in ELisp?

[Marcin Borkowski <mbork@mbork.pl>]

On 2015-12-29, at 19:23, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Cc: Emacs-devel@gnu.org
>> Date: Tue, 29 Dec 2015 18:37:40 +0100
>> 
>> > Because it needs to determine the new window-start which is a
>> > window-full above or below the current one, without assuming that all
>> > the lines have the same height in pixels.  How do you do that in Lisp?
>> > (The current implementation simulates display.)
>> 
>> Interesting, though I know too little about Emacs internals to fully
>> understand your answer.  I thought it just does something like
>> 
>> (save-excursion
>>   (other-buffer)
>>   (scroll-up))
>> 
>> Why my (probably naïve) implementation won't work?
>
> (You forget other-window-for-scrolling, but that's beside the point.)

Yes.

> How would that help?  The guts are in scroll-up, which is in C (as all
> the scrolling commands).

Well, I should have written explicitly what's wrong with the current
implementation.

When I view a pdf (in pdf-tools as well as in doc-view-mode), I'd like
C-M-v / C-M-S-v to change page when they reach the bottom/top of the
page.  Currently, they don't do it, which is a Very Bad Thing™.

Now that I think of it, I guess rewriting scroll-other-window in Elisp
wouldn't help a lot - I'd probably still have to advise them, or else
C-M-v should check what is bound to <next> and <prior> in the buffer to
be scrolled.  Does anyone have a better idea how to be able to scroll
a pdf in other window using C-M-v and C-M-S-v?

TIA,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University