Re: Can we make set_point_both less expensive?

[Daniel Colascione <dancol@dancol.org>]

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On 03/16/2015 12:42 PM, Eli Zaretskii wrote:
>> Date: Mon, 16 Mar 2015 11:31:57 -0700
>> From: Daniel Colascione <dancol@dancol.org>
>> CC: monnier@IRO.UMontreal.CA, emacs-devel@gnu.org
>>
>>> I wasn't talking about intangible, I was talking about the
>>> point-entered and point-exited properties.
>>>
>>> Stefan argues that these should actually be cursor-entered/exited,
>>> i.e. we should run the hooks when we know that point has the value
>>> that will be used to set the cursor there.  But doing that before
>>> redisplay doesn't guarantee that, since redisplay sometimes moves
>>> point to bring it into view.  So in that case, the hooks might run
>>> when they shouldn't have, or vice versa.
>>
>> Sure, but intangible is the most useful facility we're talking about
>> disabling by default. Aren't point-entered and point-exited even less
>> useful? Looking through the source, ERC uses these hooks to echo
>> timestamps, which it could do just as well with a post-command-hook.
>> Gnus does something similar to update its toolbar. table also uses these
>> hooks to refresh its menu bar.
> 
> My understanding was that Stefan wants these hooks replaced with
> different ones, not throw them away.  So I was talking about those
> different hooks.

I don't see a good use case for either the old or the new hook. Instead
of making point motion updates "edge triggered" (i.e., run a function
when point enters or exits a certain region), modes should be using a
"level triggered" approach, where they inspect the current location of
point and update whatever state they need based on that current location.


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