Path: utzoo!utgpu!watmath!uunet!tut.cis.ohio-state.edu!GODOT.PSC.EDU!gentzel
From: gentzel@GODOT.PSC.EDU (David Gentzel)
Newsgroups: gnu.emacs.bug
Subject: Redisplay bug (18.{47,49,53})
Message-ID: <8903230425.AA23582@godot.psc.edu>
Date: 23 Mar 89 04:25:47 GMT
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: GNUs Not Usenet
Lines: 27

I ran into a redisplay bug today which I've been able to reproduce on 18.47,
18.49, and 18.53 with both vt200 and vt52 terminal types.  It has to do with
the interaction between tabs and horizontal scrolling.

To reproduce (in an 80 column window) execute the following:
(progn
    (switch-to-buffer "*bug*")
    (erase-buffer)
    (insert "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
	    "xxxxxxxxxxxxxxxx\t    \nx\n")
    (goto-char (point-min))
    (scroll-left nil)
    (end-of-line))

Now type ^G^E^?.  Note that you've deleted a single space, but the redisplay
is wrong.  A ^L fixes things up.

The ^G^E is not strictly necessary, but seems to set things up to allow the
bug to be consistently reproduced.

I've looked at the code briefly but have admitted defeat (for the moment at
least).  Anyone have any ideas?

					Dave Gentzel
					Pittsburgh Supercomputing Center
					gentzel@godot.psc.edu
					or gentzel@morgul.psc.edu