Re: Very long lines in shell-mode

[Richard Stallman]

    Most likely the 2MB line will be inserted in the buffer in many little
    chunks of maybe 4KB or so: for each chunk font-lock may decide to refontify
    the whole line.  Each fontification step takes time proportional to the
    length of the line, so you get O(n^2) behavior.

    And this is without even considering the regexps involved which may very
    likely add a factor of n to that.

    Maybe for such cases, font-lock should have a "sanity check" and either not
    fontify the line at all, or fontify only a part of it at a time.

A possible simple solution: in Shell mode, don't fontify a line that
doesn't end in a newline.  If that solves the problem, it would be
simple enough to install now.