bug#7117: 23.2.2 mangles terminal escape sequences

[Ryan Johnson <ryanjohn@ece.cmu.edu>]

  On 9/30/2010 5:44 PM, Eli Zaretskii wrote:
>> Date: Thu, 30 Sep 2010 17:14:16 +0200
>> From: Ryan Johnson<ryanjohn@ece.cmu.edu>
>> CC: monnier@iro.umontreal.ca, 7117@debbugs.gnu.org
>>
>>>>    From the above, it seems that scrolling past beginning or end of buffer
>>>> triggers an error, which I guess is somewhat justifiable.
>>> Indeed.  Perhaps we need some infrastructure to ignore errors in this
>>> case (I assume `ignore-errors' won't help).  Or maybe we should allow
>>> not to discard input when we signal an error.  Or maybe discard-input
>>> should be smarter, and not discard partial escape sequences?
>> One thing I don't get is, I've been using emacs over painfully slow ssh
>> connections for literally years -- sometimes slow enough that keystrokes
>> take visible time to echo. This was never really an issue before.
> What would you expect to see, that would cause you think it was "an
> issue"?  When Emacs is keyboard-driven, typing text and scrolling
> commands seldom happen in such a quick succession that hitting end of
> buffer while scrolling would discard text you typed meanwhile.  And
> even if it did, how would you know for sure you actually typed it?
It's not just keyboard driven. It's a mouse-enabled terminal and the 
mouse click/wheel actions cause the issues (each one generates a burst 
of 6-12 characters). As you say, I don't think I've ever seen this 
happen with keyboard input; pasting commands from a remote X clipboard 
might have a similar effect, but I've never tried.

In the past, scrolling once or twice past buffer begin/end wasn't 
guaranteed to dump garbage. It would just beep/flash most of the time, 
and the slow network connection didn't seem to make it worse. Now, if 
I'm not on intranet, virtually every scroll past-end will dump garbage 
somewhere.

Also, the problem I hit this morning was not related to fast 
typing/clicking over a slow connection. I was doing an ediff-files 
session, and about every other time I clicked on a buffer to edit a 
conflict, emacs would reward me with a mangled escape code... sometimes 
where point had been and sometimes where it ended up. I wasn't typing 
fast or clicking madly -- it was more like "a n n n n b n n <stare a 
while> <click> <grumble> <clean up mess>"

The latter problem went away once I got to work and had a fast network; 
and the former happens much less frequently here (unless I give the 
wheel a really good spin, but that's understandable).

Ryan