bug#75342: [PATCH] Speed up asynchronous man page fontifying

["Björn Bidar via Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Björn Bidar <bjorn.bidar@thaodan.de>
>> Cc: Stefan Kangas <stefankangas@gmail.com>,  75342@debbugs.gnu.org,
>>   juri@linkov.net
>> Date: Sat, 04 Jan 2025 11:33:18 +0200
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> >> When I set `Man-prefer-synchronous-call` to t, it takes ~1.8 seconds to
>> >> process the same page.  I guess that this is the lower bound for how
>> >> fast we could make the asynchronous call.
>> >
>> > Why not make Man-prefer-synchronous-call t by default, then?
>> 
>> The call might take longer on slower machines (or network connections)
>> and then block Emacs until the call was done.
>
> Slower connections (I'm guessing you mean remote man pages?) could be
> recognized exempted from synchronous operation.

Yeah that's what I meant.

> As for slower machines: this is a defcustom, so users of slower machines can
> customize it if the synchronous formatting is too long for them.

I don't know yes its customizable but it could lead to some surprises.

>> Never block ui unless you can do avoid it.
>
> Except that this comes at a price here: the time until I can see the
> full man page could be very long.  So this is not a back-and-white
> situation.

Why is the price so high? The time to call man should be the same in
both asynchronous and synchronous call.