bug#29057: 26.0.60; sgml-mode should define completion-at-point-functions

[Tom Tromey <tom@tromey.com>]

sgml-mode has a lot of data about tags and attributes, but it doesn't
provide a convenient way to do completion of them; only things like
sgml-tag and sgml-attributes.

I think sgml-mode should set completion-at-point-functions to a function
that can complete attributes without querying the user in the minibuffer.

Tom


In GNU Emacs 26.0.60 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.22.21)
 of 2017-10-07 built on bapiya
Repository revision: 0fa353b50476329531307905f23ed2b172a6e9fc
Windowing system distributor 'Fedora Project', version 11.0.11903000
System Description:	Fedora release 26 (Twenty Six)

Recent messages:
Auto-saving...done
Mark set
Sending...
Mark set [2 times]
Sending via mail...
Sending email 
Sending email done
Sending...done
C-x C-g is undefined
Scanning for dabbrevs...done

Configured using:
 'configure --prefix=/home/tromey/Emacs/install --with-modules
 --with-file-notification=inotify'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
GNUTLS LIBXML2 FREETYPE LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11
MODULES LCMS2

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

Major mode: Emacs-Lisp

Minor modes in effect:
  diff-auto-refine-mode: t
  flyspell-mode: t
  which-function-mode: t
  shell-dirtrack-mode: t
  erc-services-mode: t
  erc-list-mode: t
  erc-menu-mode: t
  erc-autojoin-mode: t
  erc-ring-mode: t
  erc-networks-mode: t
  erc-pcomplete-mode: t
  erc-track-mode: t
  erc-match-mode: t
  erc-netsplit-mode: t
  erc-hl-nicks-mode: t
  erc-button-mode: t
  erc-fill-mode: t
  erc-stamp-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  savehist-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  auto-fill-function: do-auto-fill
  transient-mark-mode: t

Load-path shadows:
/home/tromey/.emacs.d/elpa/bubbles-0.5/bubbles hides /home/tromey/Emacs/install/share/emacs/26.0.60/lisp/play/bubbles

Features:
(company-tests company-oddmuse company-keywords company-etags
company-gtags company-dabbrev-code company-dabbrev company-files
company-capf company-cmake company-xcode company-clang company-semantic
company-eclim company-template company-css company-nxml company-bbdb
company cursor-sensor mhtml-mode css-mode eww js json sgml-mode
time-stamp autoconf autoconf-mode sh-script smie executable finder
lisp-mnt tcl dired-aux gud pcmpl-unix pcmpl-gnu whitespace descr-text
url-http url-gw url-auth texinfo gnus-fun calc calc-loaddefs calc-macs
vc-annotate shadow emacsbug cc-awk mode-local completion erc-replace
delsel rect cl-print debug cus-edit gdb-shell novice log-edit make-mode
org-bullets org-rmail org-mhe org-irc org-info org-gnus org-docview
doc-view image-mode org-bibtex bibtex org-bbdb org-w3m org-element
avl-tree generator org org-macro org-footnote org-pcomplete org-list
org-faces org-entities noutline outline org-version ob-emacs-lisp ob
ob-tangle org-src ob-ref ob-lob ob-table ob-keys ob-exp ob-comint
ob-core ob-eval org-compat org-macs org-loaddefs jka-compr flow-fill
gnus-html url-queue help-fns radix-tree url-cache mm-url url url-proxy
url-privacy url-expand url-methods url-history url-cookie url-domsuf
url-util supercite regi nnir shr-color shr svg xml dom browse-url
goto-addr find-file pulse etags xref project find-dired mail-hist ffap
copyright perl-mode vc-mtn vc-hg conf-mode tabify man dabbrev term/xterm
xterm bug-reference map cc-mode cc-fonts cc-guess cc-menus cc-cmds
smerge-mode log-view pcvs-util vc-bzr vc-src vc-sccs vc-svn vc-cvs
vc-rcs add-log vc-git diff-mode rust-mode misc mailalias sort smiley
gnus-cite mm-archive gnus-async gnus-bcklg mail-extr gnus-ml disp-table
misearch multi-isearch gnus-topic nndraft nnmh nnfolder utf-7
network-stream nsm starttls gnus-agent gnus-srvr gnus-score score-mode
nnvirtual gnus-msg nntp gnus-cache gnus-registry registry ebdb-gnus
gnus-art mm-uu mml2015 mm-view mml-smime smime dig mailcap gnus-sum
gnus-group gnus-undo smtpmail gnus-start gnus-cloud nnimap nnmail
mail-source tls gnutls utf7 netrc nnoo gnus-spec gnus-int gnus-range
gnus-win gnus nnheader elec-pair flyspell ispell diminish projectile
ibuf-macs grep compile ibuf-ext ibuffer ibuffer-loaddefs dash appt
diary-lib diary-loaddefs which-func imenu tramp tramp-compat
tramp-loaddefs trampver ucs-normalize shell parse-time minimap
autorevert filenotify cus-start cus-load status erc-services erc-list
erc-menu erc-join erc-ring erc-networks erc-pcomplete pcomplete
erc-track erc-match erc-netsplit erc-hl-nicks easy-mmode color
erc-button erc-fill erc-stamp wid-edit erc-goodies erc erc-backend
erc-compat thingatpt pp warnings advice vc-dir ewoc vc vc-dispatcher
cc-styles cc-align cc-engine cc-vars cc-defs ebdb-complete ebdb-message
sendmail message rmc puny dired dired-loaddefs format-spec rfc822 mml
mml-sec epa epg gnus-util rmail rmail-loaddefs mm-decode mm-bodies
mm-encode mail-parse rfc2231 rfc2047 rfc2045 mm-util ietf-drums
mail-prsvr mail-utils gmm-utils mailheader ebdb-mua ebdb-com derived
edmacro kmacro crm mailabbrev ebdb-format qp ebdb cl-extra help-mode
eieio-opt speedbar sb-image ezimage dframe find-func eieio-base pcase
subr-x cal-menu calendar cal-loaddefs timezone ange-ftp comint
ansi-color ring server savehist finder-inf dwarf-mode-autoloads
gdb-shell-autoloads lisppaste-autoloads pydoc-info-autoloads info-look
info cl weblogger-autoloads package easymenu epg-config url-handlers
url-parse auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs
password-cache url-vars seq byte-opt gv bytecomp byte-compile cconv
cl-loaddefs cl-lib time-date mule-util 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 menu-bar rfn-eshadow isearch timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame 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 minibuffer 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 dbusbind inotify lcms2 dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty
make-network-process emacs)

Memory information:
((conses 16 4163433 436624)
 (symbols 48 95876 9)
 (miscs 40 52447 22780)
 (strings 32 717121 49509)
 (string-bytes 1 22727568)
 (vectors 16 286296)
 (vector-slots 8 5060984 292719)
 (floats 8 590 1321)
 (intervals 56 563691 5939)
 (buffers 992 543))