font-lock-add-keywords in hi-lock.el

[Juri Linkov]

hi-lock-mode breaks existing highlighting when its regexps cover
areas highlighted by standard font-lock keywords (non-syntactic).
This is especially undesirable on large highlighted areas like
outline headings etc.

A good solution for this problem is to append new hi-lock keywords
at the end of the current highlighting list instead of adding them
at the beginning.  Thus hi-lock regexps always will be placed over
standard highlighted keywords.

A patch below sets the 3rd arg `HOW' (former `APPEND') of
`font-lock-add-keywords' to t.  (The parameter `OVERRIDE' of the
MATCH-HIGHLIGHT form is already t on every hi-lock keyword, so this
will work correctly.)

Index: lisp/hi-lock.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/hi-lock.el,v
retrieving revision 1.35
diff -c -r1.35 hi-lock.el
*** lisp/hi-lock.el     10 Dec 2005 11:47:28 -0000      1.35
--- lisp/hi-lock.el     14 Dec 2005 17:07:29 -0000
***************
*** 526,532 ****
    "Highlight REGEXP with face FACE."
    (let ((pattern (list regexp (list 0 (list 'quote face) t))))
      (unless (member pattern hi-lock-interactive-patterns)
!       (font-lock-add-keywords nil (list pattern))
        (push pattern hi-lock-interactive-patterns)
        (let ((buffer-undo-list t)
            (inhibit-read-only t)
--- 543,549 ----
    "Highlight REGEXP with face FACE."
    (let ((pattern (list regexp (list 0 (list 'quote face) t))))
      (unless (member pattern hi-lock-interactive-patterns)
!       (font-lock-add-keywords nil (list pattern) t)
        (push pattern hi-lock-interactive-patterns)
        (let ((buffer-undo-list t)
            (inhibit-read-only t)
***************
*** 544,550 ****
    (when (or hi-lock-file-patterns patterns)
      (font-lock-remove-keywords nil hi-lock-file-patterns)
      (setq hi-lock-file-patterns patterns)
!     (font-lock-add-keywords nil hi-lock-file-patterns)
      (font-lock-fontify-buffer)))
  
  (defun hi-lock-find-patterns ()
--- 561,567 ----
    (when (or hi-lock-file-patterns patterns)
      (font-lock-remove-keywords nil hi-lock-file-patterns)
      (setq hi-lock-file-patterns patterns)
!     (font-lock-add-keywords nil hi-lock-file-patterns t)
      (font-lock-fontify-buffer)))
  
  (defun hi-lock-find-patterns ()
***************
*** 573,580 ****
  (defun hi-lock-font-lock-hook ()
    "Add hi lock patterns to font-lock's."
    (if font-lock-mode
!       (progn (font-lock-add-keywords nil hi-lock-file-patterns)
!            (font-lock-add-keywords nil hi-lock-interactive-patterns))
      (hi-lock-mode -1)))
  
  (provide 'hi-lock)
--- 590,598 ----
  (defun hi-lock-font-lock-hook ()
    "Add hi lock patterns to font-lock's."
    (if font-lock-mode
!       (progn
!       (font-lock-add-keywords nil hi-lock-file-patterns t)
!       (font-lock-add-keywords nil hi-lock-interactive-patterns t))
      (hi-lock-mode -1)))
  
  (provide 'hi-lock)

-- 
Juri Linkov
http://www.jurta.org/emacs/