Mapping Font Fallbacks

ATSUI provides the following functions for fallback mapping:

ATSUSetFontFallbacks indicates the fonts to search and the search order to use when fallback mapping is needed.
ATSUGetFontFallbacks obtains the fonts to employ and search order to use when fallback mapping is required.
ATSUMatchFontsToText obtains the first subrange of text whose character(s) cannot be drawn with the assigned font and recommends a substitute font.
ATSUSetTransientFontMatching provides automatic font substitution when a character(s) cannot be drawn with the assigned font.
ATSUGetTransientFontMatching indicates whether automatic font substitution is enabled.