Subject: bug#14134: 24.3; Delphi Mode Doesn't Work With Highlight Changes Mode

From: Erik Knowles <[email-masked]>
Date: Wed, 3 Apr 2013 14:03:36 -0600

Delphi mode's fontification code erases all existing text properties, including those used by highlight
changes mode to mark modified text sections. 

To duplicate:

emacs -Q
<emacs responds with the scratch buffer>
M-x delphi-mode
M-x highlight-changes-mode
<type some text -- the text will be shown with the highlight-changes face>
M-x highlight-changes-visible-mode
<text is shown in the default face>
M-x highlight-changes-visible-mode
<At this point the text will still be shown in the default face instead of the
highlight-changes face>

I've not included a proper patch (intuitively, the "correct" fix would be to rewrite Delphi mode's
fontification code to use overlays) because I'm not experienced enough with Elisp to do a
proper job; however, I've personally worked around the problem by monkey patching 
as follows:

-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

;; Delphi-mode marks literals with special text properties, in the process borking *all*
;; existing properties including the properties used by hilit-chg mode for marking
;; changes even when the "changes visible" flag is off. To avoid this, the mode's
;; "delphi-set-text-properties" function is replaced here with a version that simply
;; removes the specific text properties used by the font lock while leaving all the
;; other properties alone.
;;
;; To do this delphi-set-text-properties simply tracks which faces are used by the Delphi
;; font lock code and only removes those faces
(setq delphi-used-faces (list))
(defun delphi-set-text-properties (from to properties)
  ;; Like `set-text-properties', except we do not consider this to be a buffer
  ;; modification.
  (delphi-save-state 
    (dolist (prop delphi-used-faces) (remove-text-properties from to prop))
    (when properties
      (add-text-properties from to properties)
      (add-to-list 'delphi-used-faces properties) 
    )
  ) 
)                   

-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

In GNU Emacs 24.3.1 (i686-pc-cygwin)
 of 2013-03-11 on fiona
Configured using:
 `configure '--srcdir=/home/kbrown/src/cygemacs/emacs-24.3-1/src/emacs-24.3'
 '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sbindir=/usr/sbin'
 '--libexecdir=/usr/lib' '--datadir=/usr/share' '--localstatedir=/var' '--sysconfdir=/etc'
 '--datarootdir=/usr/share' '--docdir=/usr/share/doc/emacs' '-C' '--with-x=no' 'CC=gcc'
 'CFLAGS=-ggdb -O2 -pipe
 -fdebug-prefix-map=/home/kbrown/src/cygemacs/emacs-24.3-1/build=/usr/src/debug/emacs-24.3-1
 -fdebug-prefix-map=/home/kbrown/src/cygemacs/emacs-24.3-1/src/emacs-24.3=/usr/src/debug/emacs-24.3-1'
 'LDFLAGS=-L/usr/lib/ncursesw' 'LIBS=' 'CPPFLAGS=-I/usr/include/ncursesw''

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  flyspell-mode: t
  shell-dirtrack-mode: t
  mouse-wheel-mode: t
  xterm-mouse-mode: t
  global-subword-mode: t
  subword-mode: t
  cua-mode: t
  desktop-save-mode: t
  show-paren-mode: t
  global-highlight-changes-mode: t
  highlight-changes-mode: t
  which-function-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
  line-number-mode: t
  auto-fill-function: do-auto-fill
  transient-mark-mode: t

Load-path shadows:
/home/Erik/.emacs.d/indent hides /usr/share/emacs/24.3/lisp/indent

Features:
(shadow gnus-util mail-extr emacsbug message format-spec rfc822 mml mml-sec mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils server flyspell ispell ido tempbuf
grep-a-lot grep bash-completion shell pcomplete init-terminal-fix saveplace tabbar mwheel
xt-mouse backup-dir backup-each-save pascal-mode+ delphi pascal subword org-install
xterm-title xterm-frobs goto-last-change cua-base sunrise-commander easy-mmode term ehelp
electric sort find-dired esh-var esh-io esh-cmd esh-opt esh-ext esh-proc esh-arg eldoc
esh-groups eshell esh-util esh-module esh-mode disp-table enriched dired-x easymenu
dired-aux dired desktop paren hl-line+ advice help-fns cl-lib advice-preload time-date
hl-line hilit-chg wid-edit which-func imenu edmacro kmacro warnings byte-opt compile
comint regexp-opt ansi-color ring tool-bar bytecomp byte-compile cconv
bash-completion-autoloads cygwin-mount-autoloads dired+-autoloads flymake-cursor-autoloads
flymake-python-pyflakes-autoloads flymake-easy-autoloads grep-a-lot-autoloads
hl-line+-autoloads icicles-autoloads pager-autoloads tabbar-autoloads tidy-autoloads
package ediff-hook vc-hooks lisp-float-type tabulated-list newcomment lisp-mode register
page menu-bar rfn-eshadow timer select mouse jit-lock font-lock syntax facemenu font-core
frame cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer loaddefs button faces
cus-face macroexp files text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote make-network-process dbusbind multi-tty
emacs)

- Erik R. Knowles