rxvt's actual line width disagreed upon between emacs/bash and stty/echo

[Jim Steele]

I'm puzzled by a terminal width behavior I'm seeing in rxvt.  It feels
like something that should be small and potentially obvious, but my
searches of the ml archives came up dry.

Please pardon the long line widths of this message; they are
intentional to demonstrate the line lengths and wrapping behavior I'm
trying to describe.

Versions:
  rxvt 2.7.9
  cygwin 1.3.17
  emacs 21.2
  bash 2.05b.0(8)-release

rxvt is invoked with:
  c:\cygwin\bin\rxvt.exe -bg black -fg white -e bash -l

When I ask stty what it thinks the size is, I'm reassured:
  $ stty size
  25 80

When I echo a long string to the screen, I'm reassured:

$ echo 0123456789-123456789-123456789-123456789-123456789-123456789-123456789-123456789-123456789
0123456789-123456789-123456789-123456789-123456789-123456789-123456789-123456789
-123456789

But when I invoke emacs -nw, the lines are "off" by one character in
width, causing a confusing display.  Emacs seems to write the first
character of certain lines at the last position of the same line, as
if it thought the tty was only 79 characters wide and was relying on
that fact for placement the first character.

A similar off-by-one effect occurs when I let bash line-wrap lengthy
command input while I'm typing it:

$ 23456789-123456789-123456789-123456789-123456789-123456789-123456789-12345678
9-123456789

Any diagnosing suggestions will be gratefully received.

JS

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