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:

>> My measurements show that 32 KiB might be a good choice, and gives a
>> ~95% speedup:
>> 
>> | Chunk size (KiB) | Completion time (s) |
>> |------------------+---------------------|
>> |                4 |                29.3 |
>> |                8 |                18.2 |
>> |               16 |                12.7 |
>> |               32 |                 7.4 |
>> |               64 |                 6.5 |
>> |              128 |                 5.4 |
>> 
>> Is this the best approach to optimize something like this, or am I
>> overlooking something obvious?  Note that I didn't add a variable for
>> the chunk size, but we could easily add one, if that'd be useful.
>> 
>> 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.

Never block ui unless you can do avoid it.