The font-lock system provides a system for major and minor modes to extend the region that is being highlighted.
In Mhtml mode, the function `mhtml--extend-font-lock-region` sometimes reduce the size of the region. If this is combined with, say, a minor mode that extends the region then Emacs could hang.
* Modify the documentation of the variable `font-lock-extend-region-functions` so that it's clear that the region should not shrink.
* Add a check in the function `font-lock-default-fontify-region` to prevent the region from shrinking even if a function tries to do so. (By ensuring that the region only extends and never shrinks, the function will always terminate.)
* Fix the problem in `mhtml--extend-font-lock-region`.
1) The function `mhtml--extend-font-lock-region should be modified so that it never shrinks the region.
In GNU Emacs 26.3 (build 1, x86_64-apple-darwin14.5.0, NS appkit-1348.17 Version 10.10.5 (Build 14F2511))
of 2019-09-02 built on
builder10-10.porkrind.orgWindowing system distributor 'Apple', version 10.3.1348
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
(New file)
funcall-interactively: End of buffer
Saving file /Users/anders/emacs/src/foreach/foo.html...
Wrote /Users/anders/emacs/src/foreach/foo.html
Char: C-j (10, #o12, #xa) point=7 of 12 (50%) column=0
Quit
Entering debugger...
Back to top level
(8 . 13) [2 times]
Configured using:
'configure --with-ns '--enable-locallisppath=/Library/Application
Support/Emacs/${version}/site-lisp:/Library/Application
Support/Emacs/site-lisp' --with-modules'
Configured features:
NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS MODULES THREADS
Important settings:
value of $LC_CTYPE: UTF-8
value of $LANG: en_SE.UTF-8
locale-coding-system: utf-8-unix
Major mode: HTML+
Minor modes in effect:
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
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
format-spec rfc822 mml mml-sec password-cache epa derived epg epg-config
gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils cl-print debug help-fns
radix-tree help-mode vc-dispatcher vc-svn mhtml-mode css-mode smie color
js advice json map imenu thingatpt cc-mode cc-fonts easymenu cc-guess
cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs sgml-mode
seq byte-opt gv bytecomp byte-compile cconv dom cl-loaddefs cl-lib
elec-pair time-date tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/ns-win ns-win ucs-normalize mule-util
term/common-win 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 threads kqueue cocoa ns multi-tty make-network-process emacs)
Memory information:
((conses 16 244001 21210)
(symbols 48 23926 1)
(miscs 40 81 268)
(strings 32 43844 1478)
(string-bytes 1 1234265)
(vectors 16 39716)
(vector-slots 8 775521 10394)
(floats 8 209 245)
(intervals 56 230 0)
(buffers 992 14))