bug#21077: 24.5; Slow printing in inferior python buffer with python-shell-enable-font-lock

[Wolfgang Jenkner]

On Thu, Jul 30 2015, Stefan Monnier wrote:

> In the case of comint modes, rather than disable font-lock we should
> refrain from font-locking the text after the last \n (since that's the
> line that keeps getting expanded, so we end up re-font-locking it O(N)
> times for a line of length N, for a total amount of work of O(N^2)).
> IIRC I have a similar hack in grep.el or compile.el.

But comint-output-filter does

(font-lock-prepend-text-property prompt-start (point)
                                               'font-lock-face
                                               'comint-highlight-prompt)

So keyword fontification seems to be inhibited anyway.  Is this done in
a particularly inefficient way?

Wolfgang (who ought to go read the source)