[ESS-bugs] Very long lines: Emacs "hang"

[Martin Maechler]

This was found because someone found that R behaved pretty  funny in
displaying very unusual UTF (unicode) characters when used as matrix
column labels:  R would write about 1 million empty characters...

Now his diagnosis was that "R starts to crawl"..
but I found that actually, it was mainly  ESS' fault.

Try this  (in a newly started emacs which you may have to kill from
the outside):

bl <- function(n) cat(rep(" ", n), "THE END\n")
bl(10)# fine
bl(200) # fine too

## but then

bl(6e6)
##  and for me, emacs starts using more and more CPU... when trying to
display the overwide line.

You can easily that there is not such a problem when you run something
like this in a "console" R.

Also, Rstudio, also takes a long time, but does better (well, and then
throws away some;
Rstudio is funny anyway:
It displays
   cat("abc")
exactly the same as
   cat("abc\n")

which is a bit "too helpful" in my view..
Martin