Created attachment 408751 [details]
Microbenchmark

On this microbenchmark, we spend 67% of the time looking up fonts (inside CTFontDescriptorCreateMatchingFontDescriptor() or CTFontDescriptorCreateMatchingFontDescriptors()).

Created attachment 408801 [details]
Patch

Created attachment 408802 [details]
Patch

Created attachment 408805 [details]
Patch

Created attachment 408806 [details]
Microbenchmark

This is a 2.2x speedup on the microbenchmark!!

Here are my numbers, units are ms, lower is better:

With patch:
1205
1201
1250
1272
1240
1250
1260
1249
1230
1233

Without patch:
3993
3928
3952
3987
3954
3967
3958
4048
3915
4030

Remaining tasks:

1. Make this patch do nothing on non-macOS ports
2. Iterate over all fonts, not just the ones returned by an empty dictionary and CTFontDescriptorCreateMatchingFontDescriptors()
3. Make sure tests pass
4. Most tests allow user-installed fonts, which won't hit this codepath. Do something to be more confident in this patch

Created attachment 408902 [details]
WIP

Created attachment 408991 [details]
Patch

Created attachment 409001 [details]
Patch

Remaining tasks:

1. Make sure tests pass
2. Most tests allow user-installed fonts, which won't hit this codepath. Do something to be more confident in this patch
3. Key the fonts on all localizations of the family name

Created attachment 409002 [details]
Patch

Created attachment 409004 [details]
Patch

Created attachment 409005 [details]
Patch

Created attachment 409006 [details]
Patch

Created attachment 409009 [details]
Patch

See also: <rdar://problem/68579484>

Created attachment 409069 [details]
Patch

Remaining task: Most tests allow user-installed fonts, which won't hit this codepath. Do something to be more confident in this patch

Created attachment 409097 [details]
Patch

Created attachment 409172 [details]
Patch

Created attachment 409196 [details]
Patch

Integrating this into Apple's build system will be quite challenging. I'll be putting this on hold to see if it's possible to solve this another way.

See also: <rdar://problem/68579484>

<rdar://problem/69330831>

I also filed <rdar://problem/69389335>

Comment on attachment 409196 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=409196&action=review

> Source/WebCore/platform/graphics/cocoa/PreinstalledFonts.mm:119
> +        prebuiltFontFamilyMembers(familyName);

I think this should be `return prebuiltFontFamilyMembers(familyName)`. After making that change I got the expected speedup from prototyping the patch.

Comment on attachment 409196 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=409196&action=review

> Source/WebCore/platform/graphics/cocoa/PreinstalledFonts.mm:119
> +        prebuiltFontFamilyMembers(familyName);

I think this should be `return prebuiltFontFamilyMembers(familyName)`. After making that change I got the expected speedup from prototyping the patch.

Created attachment 417673 [details]
Patch

Created attachment 417684 [details]
Patch

This is fixed by rdar://68579484.