Re: Display slowness that is painful

[storm@cua.dk (Kim F. Storm)]

Kenichi Handa <handa@m17n.org> writes:

> In article <m3d5i6m1vd.fsf@kfs-l.imdomain.dk>, storm@cua.dk (Kim F. Storm) writes:
>
> I think another reason of the slowness is this part (in
> set_iterator_to_next):
>
>     case GET_FROM_DISPLAY_VECTOR:
> [...]
>       /* Restore face of the iterator to what they were before the
>          display vector entry (these entries may contain faces).  */
>       it->face_id = it->saved_face_id;
>
>       if (it->dpvec + it->current.dpvec_index == it->dpend)
> 	{
> [...]
> 	  /* Recheck faces after display vector */
> 	  it->stop_charpos = IT_CHARPOS (*it);
> 	}
>       break;
>
> Because of this, it seems that handle_stop is called for
> every character after an eight bit character.  Isn't it
> possible to tune it?  First of all, why should we recheck
> faces after display vector?

2004-12-13  Kim F. Storm  <storm@cua.dk>

	* xdisp.c (set_iterator_to_next): Reset stop_charpos after display
	vector.

It was made to fix the following bug:

> From: 	Stefan Monnier
> Subject: 	Incorrect faces on display
> Date: 	Thu, 09 Dec 2004 17:15:31 -0500
> User-agent: 	Gnus/5.11 (Gnus v5.11) Emacs/21.3.50 (gnu/linux)
>
> I started seeing recently problems where elisp code gets displayed with the
> font-lock-comment-face even though it's not a comment.
>
> This always shows up right after an invisible piece of text (I use
> outline-minor-mode in elisp).
>
> I first thought it was some funny bug in font-lock or jit-lock, but a quick
> C-u C-x = shows that the text-properties are correct: the problem is in
> the redisplay.
>
> I finally came up with a recipe to reproduce it:
>
>    emacs -Q -f global-font-lock-mode -f outline-minor-mode
>
>    (; RET a RET (foobar C-u 1000 M-x hide-sublevels
>
> If all goes well, you'll see that the second line displays "(foobar" using
> font-lock-comment-face.


The following addition to my previous patch changes this to only
recheck after ellipsis.  It does indeed speed up redisplay even
more.

I cannot say whether this will break other redisplay cases though:



*** xdisp.c	24 Jan 2006 09:30:15 +0100	1.1073
--- xdisp.c	03 Feb 2006 10:28:21 +0100	
***************
*** 5694,5699 ****
--- 5714,5721 ----
  
        if (it->dpvec + it->current.dpvec_index == it->dpend)
  	{
+ 	  int recheck_faces = it->ellipsis_p;
+ 
  	  if (it->s)
  	    it->method = GET_FROM_C_STRING;
  	  else if (STRINGP (it->string))
***************
*** 5716,5723 ****
  	      set_iterator_to_next (it, reseat_p);
  	    }
  
! 	  /* Recheck faces after display vector */
! 	  it->stop_charpos = IT_CHARPOS (*it);
  	}
        break;
  
--- 5738,5746 ----
  	      set_iterator_to_next (it, reseat_p);
  	    }
  
! 	  /* Maybe recheck faces after display vector */
! 	  if (recheck_faces)
! 	    it->stop_charpos = IT_CHARPOS (*it);
  	}
        break;
  


--
Kim F. Storm <storm@cua.dk> http://www.cua.dk