Thanks for answering.

In general, IIRC, more than one unicode character could point to one GlyphID.

Curious. I assumed every GlyphID corresponds a single unicode value ...

If the font you are using does not have that character, FPC can not change that fact. I don't seem to have a font that includes MATHEMATICAL ITALIC CAPITAL B (#$1D435)

In fact, some OpenType specialized fonts already have these characters. For example, XITSMath font. The range is 'Mathematical Alphanumeric Symbols'.

When I try to assign the escape sequence #$1D435, or its corresponding decimal #119861, I get the error 'illegal char constant', because the sequence is outside the range allowed.

Characters of this type would already be in the scope of UTF16...

The most I could do was find routines that convert some values in UTF16 to UTF8, but for this range of characters that will not work, because characters like #$1D435 does not have correspondent in UTF8.