bug#44338: 27.1; EWW can't download and view pdf

[Basil L. Contovounesios]

Nicholas Harrison <nicholasharrison222@gmail.com> writes:

> I'll make a couple more comments on the original problem I
> explained. It looks like you may have identified additional
> improvements in the process.
>
> I believe the first problem for me is that both mailcap-mime-data and
> mailcap-user-mime-data are nil. This causes the `error in process
> filter: mailcap-view-mime: Symbol’s function definition is void: nil`
> and makes the pdf download and appear in Fundamental mode. This occurs
> whether I will be using doc-view-mode or pdf-view-mode. I'll use
> DocView for the rest of this example.
>
> 1. emacs -Q
> 2. M-x eww
> 3. https://www.gnu.org/software/emacs/manual/pdf/emacs-xtra.pdf
>
> This results in the error message and the following:
> image.png
>
> This can be (partially) corrected by running the following code before the 
> steps 2 and 3:
> (add-to-list 'mailcap-user-mime-data
>              '((type . "application/pdf")
>                (viewer . doc-view-mode)))
>
> This chooses a view mode for the pdf but that brings the second
> problem. This selects the default encoding of raw-text and the
> conversion fails:
>
> Instead I choose doc-view-mode manually for the eww pdf buffer:
>
> Then selecting binary for the encoding finally gets a viewable pdf:
>
> I hope this is in some way helpful.

Thanks.  I cannot reproduce these on what will be Emacs 27.2 or Emacs
28.1 on GNU/Linux.  Perhaps they have been fixed already, or are
specific to MS Windows.  If someone on MS Windows could check whether
they still occur on master and emacs-27, that would be helpful.

-- 
Basil

In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 
1.16.0, Xaw3d scroll bars)
 of 2020-11-03 built on thunk
Repository revision: f9d6e463d310db0e1931f26609d938531c56f9c3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Debian GNU/Linux bullseye/sid

Configured using:
 'configure 'CC=ccache gcc' 'CFLAGS=-O2 -march=native' --config-cache
 --prefix=/home/blc/.local --with-x-toolkit=lucid
 --with-file-notification=yes --with-x'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND GPM DBUS GSETTINGS GLIB
NOTIFY INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT
LIBOTF ZLIB TOOLKIT_SCROLL_BARS LUCID X11 XDBE XIM MODULES THREADS
LIBSYSTEMD JSON PDUMPER LCMS2

Important settings:
  value of $LANG: en_IE.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml easymenu mml-sec epa derived epg epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map text-property-search time-date
subr-x seq byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode elisp-mode
lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch
timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core term/tty-colors frame minibuffer cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice button loaddefs faces cus-face macroexp files
window text-properties overlay sha1 md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote threads dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
cairo x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 51798 5028)
 (symbols 48 6742 1)
 (strings 32 18899 1840)
 (string-bytes 1 612322)
 (vectors 16 12192)
 (vector-slots 8 168066 8842)
 (floats 8 23 45)
 (intervals 56 221 0)
 (buffers 992 10))