Re: 23.0.60; Image in before-string of overlay interferes with keymap

[Ralf Angeli <angeli@caeruleus.net>]

* Ralf Angeli (2008-02-25) writes:

> * Richard Stallman (2008-02-10) writes:
>
>> Would someone please fix this and ack?
>>
>> From: Ralf Angeli <angeli@caeruleus.net>
>> To: emacs-pretest-bug@gnu.org
>> Date: Wed, 06 Feb 2008 22:30:17 +0100
>> Subject: 23.0.60; Image in before-string of overlay interferes with keymap
>>
>> As soon as an image is used in the before-string property of an overlay,
>> mouse clicks as defined in a keymap for the propertized string are not
>> recognized anymore.
>
> As additional info, AFAICS the following change introduced the bug:
>
> 2007-10-16  YAMAMOTO Mitsuharu  <mituharu@math.s.chiba-u.ac.jp>
>
> 	* xdisp.c (handle_display_prop): Ignore display specs after
> 	replacing one when string text is being replaced.
> 	(handle_single_display_spec): Pretend as if characters with display
> 	property haven't been consumed only when buffer text is being replaced.

Some more information ...

The original report and discussion which lead to the change can be found
here: <URL:http://thread.gmane.org/gmane.emacs.devel/80216>

The ironic part here is that while the reports Joe sent were concerned
with helping to fix Emacs to better support preview-latex and folding of
TeX macros, the resulting change actually broke preview-latex.

I could narrow down the problematic part of the change.  If the
following part of the patch (diff between revision 1.1170 and 1.1171 of
xdisp.c) is reverted, the test case I sent in my original report will
work again.

@@ -4245,7 +4260,8 @@
 	  /* Say that we haven't consumed the characters with
 	     `display' property yet.  The call to pop_it in
 	     set_iterator_to_next will clean this up.  */
-	  *position = start_pos;
+	  if (BUFFERP (object))
+	    it->current.pos = start_pos;
 	}
 #endif /* HAVE_WINDOW_SYSTEM */
 

The test case Joe sent in his report will work as well, but this is
likely only due to the fact that the part shown above is not related to
strings (where an analogous change was made.)

Could somebody please help me fix this before Emacs 22.2 is released?
I'd hate to see preview-latex broken until the successor of 22.2 will
be released.

-- 
Ralf