bug#41441: 26.3; mhtml misbehaving font-lock extend region can cause Emacs to hang

[Dmitry Gutov]

On 28.05.2020 19:13, Tom Tromey wrote:
> You can enlarge (or even reduce) the region to refontify by setting
> the following variable:

This is about font-lock-extend-after-change-region-function, though, 
isn't it?

And since that variable is not a hook (or a list), it wouldn't be 
subject to inflooping problems. Though I wouldn't like this semantics 
for it either, given the name.

> I don't remember the test case.  Not sure if the self-tests cover this;
> maybe it's archived in a bug somewhere though.

Someone should take a look.

If we don't find good examples, though, and if we agree that the design 
seems sound, we can turn it off on master and see if anyone complains.