bug#57432: 27.1; doc-view-enlarge/shrink behaviour does not match documentation

[Iago]

    Hi,
    
    
    I started Emacs with emacs -Q. Then, open any pdf file and try to
    use zoom
    
    capabilities of DocView mode. Reading the DocView documentation I
    
    understand that to doc-view-enlarge, first I should type C-c (as the
    
    Prefix Command) followed by typing +. But this produces the message
    
    C-c + is undefined
    
    The way I got the zoom behaviour is typing + two consecutive times
    (++),
    
    regardless of having typed before C-c or not. I am not sure if this
    is a
    
    bug or Maybe I am not understanding the documentation in the correct
    
    way.
    
    Same happens for doc-view-shrink.
    
    I keep below all the information produced by M-x report-emacs-bug.
    
    
    Thank you!
    
    
    Best regards,
    
    Iago
    
    
    
    
    
    
    
    In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version
    3.24.24, cairo version 1.16.0)
    
    of 2021-03-28, modified by Debian built on x86-conova-01
    
    Windowing system distributor 'The X.Org Foundation', version
    11.0.12011000
    
    System Description: Debian GNU/Linux 11 (bullseye)
    
    
    Recent messages:
    
    Mark saved where search started [3 times]
    
    funcall-interactively: Buffer is read-only: #

[32 times]
C-c + is undefined
Quit

Making completion list...
previous-line: Beginning of buffer [13 times]
next-line: End of buffer [10 times]
Type "q" in help window to restore its previous buffer, C-M-v to scroll help.
M-º is undefined

Configured using:
'configure --build x86_64-linux-gnu --prefix=/usr
--sharedstatedir=/var/lib --libexecdir=/usr/lib
--localstatedir=/var/lib --infodir=/usr/share/info
--mandir=/usr/share/man --enable-libsystemd --with-pop=yes
--enable-locallisppath=/etc/emacs:/usr/local/share/emacs/27.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/27.1/site-lisp:/usr/share/emacs/site-lisp
--with-sound=alsa --without-gconf --with-mailutils --build
x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
--libexecdir=/usr/lib --localstatedir=/var/lib
--infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
--with-pop=yes
--enable-locallisppath=/etc/emacs:/usr/local/share/emacs/27.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/27.1/site-lisp:/usr/share/emacs/site-lisp
--with-sound=alsa --without-gconf --with-mailutils --with-cairo
--with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars
'CFLAGS=-g -O2
-ffile-prefix-map=/build/emacs-LlFm6W/emacs-27.1+1=. -fstack-protector-strong
-Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
-D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
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 GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD
JSON PDUMPER LCMS2 GMP

Important settings:
value of $LANG: en_GB.UTF-8
locale-coding-system: utf-8-unix

Major mode: DocView

Minor modes in effect:
recentf-mode: t
shell-dirtrack-mode: t
tooltip-mode: t
global-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
buffer-read-only: t
line-number-mode: t
transient-mark-mode: t

Load-path shadows:
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-dde hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-dde
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-bugs-l hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-bugs-l
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-tracebug hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-tracebug
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-omg-l hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-omg-l
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-sas-a hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-sas-a
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-sas-l hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-sas-l
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-omg-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-omg-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-sp5-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-sp5-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-s4-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-s4-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-site hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-site
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/make-regexp hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/make-regexp
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-utils hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-utils
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-r-xref hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-r-xref
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-noweb-mode hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-noweb-mode
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-vst-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-vst-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-pkg hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-pkg
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/mouseme hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/mouseme
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-help hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-help
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-trns hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-trns
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/essd-els hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/essd-els
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-rdired hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-rdired
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-julia hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-julia
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-sp6-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-sp6-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-mode hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-mode
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-stata-lang hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-stata-lang
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-generics hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-generics
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-s3-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-s3-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-r-completion hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-r-completion
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-r-package hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-r-package
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-sp4-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-sp4-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-custom hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-custom
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-sas-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-sas-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-inf hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-inf
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-s-lang hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-s-lang
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-swv hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-swv
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-r-a hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-r-a
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-gretl hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-gretl
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-r-gui hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-r-gui
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-sp6w-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-sp6w-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-roxy hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-roxy
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-noweb hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-noweb
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-mouse hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-mouse
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-toolbar hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-toolbar
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-rd hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-rd
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/julia-mode hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/julia-mode
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-rutils hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-rutils
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/debian-autoloads hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/debian-autoloads
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-r-flymake hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-r-flymake
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-sp3-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-sp3-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-bugs-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-bugs-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-stata-mode hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-stata-mode
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-arc-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-arc-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-lsp-l hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-lsp-l
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-r-mode hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-r-mode
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-xls-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-xls-d
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-r-syntax hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-r-syntax
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-noweb-font-lock-mode hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-noweb-font-lock-mode
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-font-lock hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-font-lock
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-autoloads hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-autoloads
/usr/share/emacs/site-lisp/elpa/ess-18.10.2/ess-jags-d hides /usr/share/emacs/site-lisp/elpa-src/ess-18.10.2/ess-jags-d

Features:
(shadow sort mail-extr emacsbug message rmc puny rfc822 mml mml-sec epa
derived epg epg-config gnus-util rmail rmail-loaddefs
text-property-search time-date mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils goto-addr view misearch
multi-isearch cl-extra help-fns radix-tree help-mode vc-git diff-mode
doc-view jka-compr image-mode exif dired dired-loaddefs recentf
tree-widget wid-edit windmove rust-utils rust-mode rx rust-rustfmt
rust-playpen rust-compile rust-cargo ess-site ess-toolbar ess-mouse
mouseme ess-swv ess-noweb ess-noweb-font-lock-mode ess-jags-d ess-bugs-l
essd-els ess-xls-d ess-vst-d ess-stata-mode ess-stata-lang cc-vars
cc-defs make-regexp ess-sp6w-d ess-sp5-d ess-sp4-d ess-sas-d ess-sas-l
ess-sas-a ess-s4-d ess-s3-d ess-omg-d ess-omg-l ess-arc-d ess-lsp-l
ess-sp6-d ess-dde ess-sp3-d ess-julia julia-mode cl ess-r-mode
ess-r-flymake flymake-proc flymake warnings thingatpt ess-r-xref xref
project ess-trns ess-r-package shell pcomplete ess-r-syntax
ess-r-completion ess-roxy ess-rd essddr noutline outline easy-mmode
hideshow ess-s-lang ess-help info ess-mode ess ess-noweb-mode ess-inf
ess-tracebug advice format-spec ess-generics compile ess-utils ido
ess-custom executable comint ansi-color ring package easymenu browse-url
url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json subr-x map url-vars seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib 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 loaddefs
button faces cus-face macroexp files 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 move-toolbar gtk x-toolkit
x multi-tty make-network-process emacs)

Memory information:
((conses 16 141240 9597)
(symbols 48 15854 1)
(strings 32 50485 2990)
(string-bytes 1 1482381)
(vectors 16 23364)
(vector-slots 8 294473 8232)
(floats 8 97 247)
(intervals 56 3302 0)
(buffers 1000 20))

--
Iago Giné-Vázquez (0000-0002-6725-2638)

Centro de Investigación Biomédica en Red de Salud Mental, Instituto de Salud Carlos III (CIBERSAM, ISCIII), Av. Monforte de Lemos, 3-5. Pabellón 11. Planta 0, 28029 Madrid, Spain
Epidemiology of Mental Health Disorders and Ageing, Institut de Recerca Sant Joan de Déu, Santa Rosa 39-57, 08950 Esplugues de Llobregat, Spain
Research, Innovation and Teaching Unit, Parc Sanitari Sant Joan de Déu, Doctor Antoni Pujadas 42, 08830 Sant Boi de Llobregat, Spain