Re: why does occur depropertize matching lines?

[Richard Stallman <rms@gnu.org>]

    Even now occur partly preserves highlighting for some lines: when
    called with a numeric prefix argument occur displays context lines
    highlighted with their original faces whereas highlighting from matching
    lines is removed.  This is too weird.  I can't find a reason for that.

I discovered that changing occur-1 to pass t for the keep-props
argument to occur-engine inverts this: it preserves the highlighting
for the actual target line, and discards it for the context lines.

That seems like a good idea to me; what do you think?

Here's the patch that does it.

*** replace.el	20 Nov 2004 16:58:11 -0500	1.190
--- replace.el	24 Nov 2004 20:51:24 -0500	
***************
*** 915,921 ****
  		    (and case-fold-search
  			 (isearch-no-upper-case-p regexp t))
  		    list-matching-lines-buffer-name-face
! 		    nil list-matching-lines-face nil)))
  	(let* ((bufcount (length active-bufs))
  	       (diff (- (length bufs) bufcount)))
  	  (message "Searched %d buffer%s%s; %s match%s for `%s'"
--- 915,921 ----
  		    (and case-fold-search
  			 (isearch-no-upper-case-p regexp t))
  		    list-matching-lines-buffer-name-face
! 		    nil list-matching-lines-face t)))
  	(let* ((bufcount (length active-bufs))
  	       (diff (- (length bufs) bufcount)))
  	  (message "Searched %d buffer%s%s; %s match%s for `%s'"


    However, I see another problem: matches are not highlighted anymore
    with `list-matching-lines-face' because when a character has two properties

      font-lock-face [bold]                   ;; from `list-matching-lines-face'
      face           [font-lock-keyword-face] ;; from source buffer

    `face' property takes precedence over `font-lock-face'.

I wonder why occur-engine uses font-lock-face.  It is not font lock
mode, after all.  Changing it to use `face' instead makes it seem
to do the right thing.  Does it cause any problem?

*** replace.el	20 Nov 2004 16:58:11 -0500	1.190
--- replace.el	24 Nov 2004 20:53:47 -0500	
***************
*** 998,1004 ****
  					     (append
  					      `(occur-match t)
  					      (when match-face
! 						`(font-lock-face ,match-face)))
  					     curstring)
  			(setq start (match-end 0))))
  		    ;; Generate the string to insert for this match
--- 998,1004 ----
  					     (append
  					      `(occur-match t)
  					      (when match-face
! 						`(face ,match-face)))
  					     curstring)
  			(setq start (match-end 0))))
  		    ;; Generate the string to insert for this match