Re: Redisplay issues with 'space' display properties on overlays

[dalanicolai]

Or actually simpler, for the first question, with pdf-tools installed,

- first load pdf-scroll.el (after first setting the path to papyrus.el at the beginning

of the file)

- open some pdf and scroll down/up a few pages

- now split the buffer (the page in the second window does not display)

- then do `M-: (print "test"), and 'hide' the echo area by pressing `esc`

Now the page will display.

So my question is, which 'action' is responsible for getting that page displayed

(I guess it is just the vscroll does not get set, because when splitting the window

immediately after opening, without scrolling, then the page in the other window

does get displayed).

On Sat, 16 Apr 2022 at 20:17, dalanicolai <dalanicolai@gmail.com> wrote:

Well, for the second question, just do emacs -q,

 then load papyrus.el and do `M-x papyrus-demo`.

For the first question pdf-tools is required to be installed,

I am not sure how to achieve that from emacs -q

(well besides building the server manually, after installing

pdf-tools using `list-packages` I guess).

So maybe you could answer/comment on the second question.

And maybe someone who has pdf-tools installed can

answer/comment on the first question.

But I have commented out the 'print hack' now, so that the

instruction becomes to 'uncomment` it (and 'slurp' it as final

statements inside the `papyrus-redisplay` function`), after testing

the behavior with the lines commented out first.

On Sat, 16 Apr 2022 at 18:49, Eli Zaretskii <eliz@gnu.org> wrote:

> From: dalanicolai <dalanicolai@gmail.com>
> Date: Sat, 16 Apr 2022 18:37:24 +0200
>
> 1. papyrus.el uses the `papyrus-redisplay` function, which creates the 'scroll'
> by adding 'space' display properties to the overlays, and page images to
> the 'currently visible overlays'. The redisplay works fine on Spacemacs/Doom,
> but for vanilla Emacs, in order to 'finalize' the process requires a hack which is
> to 'print' something to the echo area, after which the 'redisplay' will finish
> and show the images.
>
> I have tried to use `redisplay/force-window-update` for this, but those do not
> seem to have the right effect.
>
> Obviously, my question is if you can tell me why the hack 'is required' and what
> would be the better way to achieve/finalize the redisplay.
>
> 2. I would expect that a specified space (space display property for the 'gap'
> overlays, i.e. the space between the pages) could be smaller than the default
> 'line-pixel-height`. However, this does not seem possible by just setting a
> smaller :height for the space display property, as the overlay will always have
> a minimum height of the default 'line-pixel-height'
>
> To see/reproduce what I mean you can simply load `papyrus.el` and do
> `M-x papyrus-demo`. You can experiment with the 'gap/space-height' by setting
> the `papyrus-gap-height`.
>
> For 'reproducing' the 'issue' of the first question, you can simply load
> pdf-scroll.el (but first set the correct path to `papyrus.el` at the beginning
> of that file. Also, pdf-scroll.el requires pdf-tools to be correctly installed).
> Subsequently, open some pdf file, and split the window. I hope you will find
> that the continuous scroll, including the functionality of the
> `pdf-tools-enabled-modes`, works perfectly fine in vanilla Emacs (scroll with arrows
> and page-down/up). Now, to see what I mean with the display 'issue' comment out the
> last two lines of the `papyrus-redisplay` function, and again try to split the
> window from the pdf buffer, you will find that the extra step of printing is
> required before the image will show correctly.

Since using the actual code requires complex setups, would you please
show simpler recipes for these two issues, ones that can be used
easily from "emacs -Q"?  Then I will try to answer your questions
above.

Thanks.