Subject: bug#38176: 27.0.50; pdf-tools images do not display

From: Lars Ingebrigtsen <[email-masked]>
Date: Sun, 17 Nov 2019 19:25:34 +0100

Óscar Fuentes <[email-masked]> writes:

> As for pdf-tools requirements, you need gcc + automake + autoconf + make
> and some extra libraries. This commands install the libraries in Debian
> and derivatives:
>
> $ sudo apt install libpng-dev zlib1g-dev
> $ sudo apt install libpoppler-glib-dev
> $ sudo apt install libpoppler-private-dev

Thanks; I got it to work now.

The bug is here:

(defun pdf-view-scroll-up-or-next-page (&optional arg)

[...]

        (when (or (= (window-vscroll) (image-scroll-up arg))

It's comparing the output of window-vscroll (which returns the position
in number-of-lines, not pixels) with the return value of
image-scroll-up, which returns a value in pixels.  It's not documented
at all what the latter function is supposed to return, so it looks like
a bug to me that pdf-tools relies on it.

(The function has changed a bit lately, but I didn't trace whether it's
really changed its return value.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no