When using a text edit application, a font (such as "Menlo") is selected to present glyphs, when the selected font doesn't contain a special glyph(such as “𠹷”, it's a simple Chinese glyph, "Menlo" doesn't contain it), Application will pick up a font for you to present it, In MacOS(Catalina), there are about 62 fonts (STBaoliSC-Regular, STKaiti, STSong, PingFangSC-Regular...) contain this glyph "𠹷", I found that almost every text edit application (vscode, sublime text, TextEdit) pick up the same font -- "PingFangSC-Regular" ,so I consider if it is every glyph has its own default font? if so, how can I get the font name?
This is handled by the "cascade list." If you want the default list, it's available through CTFontCopyDefaultCascadeListForLanguages, on a per-font basis:
import CoreText
let font = CTFontCreateWithName("Helvetica" as CFString, 12, nil)
let descriptors = CTFontCopyDefaultCascadeListForLanguages(font, nil)! as! [CTFontDescriptor]
If you wanted to see the list, you could do it this way (Core Text does not have very nice bridging to Swift):
for descriptor in descriptors {
let attributes = CTFontDescriptorCopyAttributes(descriptor) as! [String: Any]
print(attributes[kCTFontNameAttribute as String]!)
}
==>
LucidaGrande
.AppleSymbolsFB
GeezaPro
NotoNastaliqUrdu
Thonburi
Kailasa
PingFangSC-Regular
PingFangTC-Regular
AppleSDGothicNeo-Regular
PingFangTC-Regular
PingFangSC-Regular
PingFangHK-Regular
PingFangSC-Regular
HiraginoSans-W3
HiraginoSansGB-W3
KohinoorBangla-Regular
KohinoorDevanagari-Regular
KohinoorGujarati-Regular
MuktaMahee-Regular
NotoSansKannada-Regular
KhmerSangamMN
LaoSangamMN
MalayalamSangamMN
NotoSansMyanmar-Regular
NotoSansZawgyi-Regular
NotoSansOriya
SinhalaSangamMN
TamilSangamMN
KohinoorTelugu-Regular
NotoSansArmenian-Regular
EuphemiaUCAS
Menlo-Regular
STIXGeneral-Regular
Galvji
Kefa-Regular
.NotoSansUniversal
AppleColorEmoji
PingFangSC-Regular is the first East Asian font in the list, so it's going to be the one picked to replace Helvetica. It's also the first East Asian font in the cascade list for Lucida Grande, and Helvetica Neue. And it's kind of straight-forward, even boring, font. But if you were using a bit more unusual font, like American Typewriter? Well, that would be replaced with Songti, which is a bit lighter. Marker Felt replaces with Kaiti, which has more variation on the stoke widths (though IMO it would be much better to replace it with Kaiti Black rather than Regular). I don't know of any built-in Asian fonts that are as "fun" as the available Latin fonts, but if you had one, you can customize the cascade list to choose it instead (using NSFontDescriptor on Mac, or UIFontDescriptor on iOS).
If you want more details about cascade lists, see the WWDC 2018 video, Creating Apps for a Global Audience.