bug#42824: 26.3; Feature request: implement 'smooth scroll' in djvu.el package

[dalanicolai]

FYI it is inspired by `pdf-view-next-line-or-next-page` (and complement) of the pdf-tools package.

On Mon, 26 Oct 2020 at 22:43, Lars Ingebrigtsen <larsi@gnus.org> wrote:

Roland, could you take a look at this suggestion -- I've not used
djvu.el myself, so I'm not sure whether this would make sense or not:

dalanicolai@gmail.com writes:

> The djvu.el pacakge is a beautiful package but unfortunately it is not
> designed for reading djvu documents (The comments in the file say it is
> meant to be used with DjView). Probably for that reason there is no
> smooth scroll over pages implemented (at least I am not aware of that
> functionality), i.e. you can scroll smoothly over a
> single page but you can only do a full page jump to a next or previous
> page.
> This means that when you are at the bottom/top of a page and jump to
> the
> next/previous page then you end up at the bottom/top of that page,
> which is annoying. Anyway, smooth scrolling can be implemented with
> only
> a view simple lines. So I would like to propose to add the following
> lines to djvu.el:
>
>     (defun djvu-scroll-up-or-next-page ()
>       (interactive)
>       (scroll-up-line 5)
>       (when (= (window-vscroll) 0)
>         (djvu-next-page 1)))
>
>     (defun djvu-scroll-down-or-previous-page ()
>       (interactive)
>       (if (not (= (window-vscroll) 0))
>           (scroll-down-line 5)
>         (djvu-prev-page 1)
>         (scroll-up-command))))
>
> By adding these lines emacs can be perfectly used as a djvu reader
> (although it does not show annotations).

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