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Re: Criticism of jit-lock--antiblink-post-command

From: Eli Zaretskii
Subject: Re: Criticism of jit-lock--antiblink-post-command
Date: Wed, 27 Nov 2019 18:10:34 +0200

> From: Stefan Monnier <address@hidden>
> Cc: address@hidden,  address@hidden,  address@hidden
> Date: Wed, 27 Nov 2019 08:46:41 -0500
> >> The intention is that when it's not useful it's harmless.
> >> IOW if there's a good reason to turn it off, it's probably a bug.
> > I don't think I agree.  A post-command-hook that is not useful just
> > takes CPU cycles, and likewise a timer which does nothing when its
> > function is invoked.
> AFAIK we don't try very hard to avoid such waste.

We should, though.

> E.g. every time we run redisplay, it will check at every position if
> there is a `display` or `invisible` property, even in those buffers
> where no code ever has nor ever will add one of those properties.

No, the display engine doesn't check for these properties at every
position, it only checks that at positions where some property
changes (by looking at the interval tree).

And properties can be added manually, not just by code, btw.

> > And in any case, a feature that changes behavior should have a knob to
> > disable it.
> We like such knobs in Emacs, indeed.  My argument was not against having
> such a knob

Well, by saying "if it needs to be turned off, it's a bug", you seemed
to be saying that it doesn't need to be turned off.  Apologies for my

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