I wrote Horizontal.py as an extension in order to avoid forking IDLE. It 
should be simple to incorporate a toggling horizontal scroll bar within 
the EditorWindow class itself.
> (Note: it would seem nice to be able to get a list of extensions available and those enabled from the menu. Or is there a reason not too?)

IdleX provides a dialog for enabling and disabling extensions.

The shell window has wrapping enabled on its text widget. A horizontal 
bar is not needed there.
> 2. Edit windows are not limited to python code. Else they would *always* syntax hilight. Or Pycode might be embedded in other formats. If #6858 were implemented, h scroll would be more useful.
True. The Editor window does not wrap, which is why the horizontal bar 
is needed there.
> 3. Not everyone agrees with the 80 char limits.
The limit does make printing code simpler, however.  But that's a 
separate discussion.
> 4. People sometimes edit a file written by someone else.
Yes, and often times it is one or two lines in the file that extend 
beyond the right border of the editor.
> Counter-arguments:
> 1. A full screen window allows about 200 chars or more, which is enough for any code entry and most print output and most 'files written by someone else'.
I shouldn't have to resize the editor to see its contents.
> 2. For exceptions, put cursor on long line and use =>  arrow key.
>
> ----------
> nosy: +serwy, terry.reedy
> resolution: rejected ->
> status: closed ->  open
> versions: +Python 3.4
>
> _______________________________________
> Python tracker<report@bugs.python.org>
> <http://bugs.python.org/issue1207613>
> _______________________________________
>