Re: Is there something like `on-display-functions'?

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 27 Jan 2010 15:37:33 +0000
> From: Alan Mackenzie <acm@muc.de>
> Cc: Lennart Borgman <lennart.borgman@gmail.com>, emacs-devel@gnu.org
> 
> > I'd recommend you use jit-lock instead (via jit-lock-register), tho,
> > because fontification-functions (despite its name) really only works
> > well with a single function (at least I don't know how to make it work
> > well with more than one, based on how it's currently defined).
> 
> Is that because it's got to set 'fontified' properties?

No, I don't think so.  The handler of the `fontified' property checks
for the property's value being nil only once, and then runs all the
functions in fontification-functions in a loop.  The relevant code is
below.

Stefan, could you perhaps show a reproducible test case for this?

 ----------------------------------------------------------------------
  /* Get the value of the `fontified' property at IT's current buffer
     position.  (The `fontified' property doesn't have a special
     meaning in strings.)  If the value is nil, call functions from
     Qfontification_functions.  */
  if (!STRINGP (it->string)
      && it->s == NULL
      && !NILP (Vfontification_functions)
      && !NILP (Vrun_hooks)
      && (pos = make_number (IT_CHARPOS (*it)),
	  prop = Fget_char_property (pos, Qfontified, Qnil),
	  /* Ignore the special cased nil value always present at EOB since
	     no amount of fontifying will be able to change it.  */
	  NILP (prop) && IT_CHARPOS (*it) < Z))
    {
      int count = SPECPDL_INDEX ();
      Lisp_Object val;

      val = Vfontification_functions;
      specbind (Qfontification_functions, Qnil);

      if (!CONSP (val) || EQ (XCAR (val), Qlambda))
	safe_call1 (val, pos);
      else
	{
	  Lisp_Object globals, fn;
	  struct gcpro gcpro1, gcpro2;

	  globals = Qnil;
	  GCPRO2 (val, globals);

	  for (; CONSP (val); val = XCDR (val))
	    {
	      fn = XCAR (val);

	      if (EQ (fn, Qt))
		{
		  /* A value of t indicates this hook has a local
		     binding; it means to run the global binding too.
		     In a global value, t should not occur.  If it
		     does, we must ignore it to avoid an endless
		     loop.  */
		  for (globals = Fdefault_value (Qfontification_functions);
		       CONSP (globals);
		       globals = XCDR (globals))
		    {
		      fn = XCAR (globals);
		      if (!EQ (fn, Qt))
			safe_call1 (fn, pos);
		    }
		}
	      else
		safe_call1 (fn, pos);
	    }

	  UNGCPRO;
	}

      unbind_to (count, Qnil);