GNU bug report logs - #71454
30.0.50; Performance issues with font selection

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Message #82 received at 71454 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Gerd Möllmann <gerd.moellmann <at> gmail.com>,
 mituharu <at> math.s.chiba-u.ac.jp
Cc: luangruo <at> yahoo.com, justksqsf <at> gmail.com, 71454 <at> debbugs.gnu.org,
 alan <at> idiocy.org
Subject: Re: bug#71454: 30.0.50; Performance issues with font selection
Date: Sat, 12 Oct 2024 14:20:21 +0300

Ping!

> From: Gerd Möllmann <gerd.moellmann <at> gmail.com>
> Cc: Kai Ma <justksqsf <at> gmail.com>,  Alan Third <alan <at> idiocy.org>,  Po Lu
>  <luangruo <at> yahoo.com>,  71454 <at> debbugs.gnu.org, YAMAMOTO Mitsuharu
>  <mituharu <at> math.s.chiba-u.ac.jp>
> Date: Sat, 28 Sep 2024 05:36:32 +0200
> 
> Eli Zaretskii <eliz <at> gnu.org> writes:
> 
> >> From: Kai Ma <justksqsf <at> gmail.com>
> >> Date: Fri, 27 Sep 2024 00:42:04 +0200
> >> 
> >> I got back to this problem today and have some initial ideas.
> >> 
> >> I did some profiling and the profiler clearly shows that most CPU
> >> time was in macfont_list and
> >> CTFontDescriptorCreateMatchingFontDescriptors. (screenshot attached
> >> below) So yes, it’s a Mac-only problem.
> >> 
> >> macfont_list will call CTFontDescriptorCreateMatchingFontDescriptors
> >> for n times, where n is the number of installed fonts. It seems
> >> CTFontDescriptorCreateMatchingFontDescriptors is very expensive, and
> >> we should minimize the use of it.
> >> 
> >> I did a quick proof-of-concept patch (attached) that removes the
> >> outer loop (utilizing CTFontDescriptorCreateMatchingFontDescriptors
> >> itself to search for fonts). And now I no longer experience long
> >> delays. It’s not complete as I haven’t adapted & incorporated
> >> mac_font_create_preferred_family_for_attributes yet.
> >> 
> >> I don’t see noticeable font differences after the change on the
> >> files I’m working on. I would like to gather some feedback from the
> >> more experienced on whether this is a promising solution or not. If
> >> it is, I will refine it into a formal patch.
> >
> > Thanks.  I'm adding a few people in the hope that they could comment
> > on the patch, or maybe try it and provide feedback.
> 
> I haven't tried the patch because I can't reproduce the problem and I
> don't use much beyond Latin-1 so I think chances are low that I'd see
> anyting breaking with the patch.
> 
> But looking at the patch, which mostly removes stuff from macfont_list,
> I wonder if/how that can be semeantically equalivalent to the existing
> code.
> 
> Just saying, I'm definitely not an expert in this area.
> 
> Adding YAMAMOTO Mitsuharu <mituharu <at> math.s.chiba-u.ac.jp>, the original
> author.
> 

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