fonttosfnt: Support Unicode supplementary-plane characters?

[Fredrik Noring]

Hi,

Any chance the X.Org fonttosfnt tool will support the Unicode supplementary-
plane characters (U+10000 to U+10FFFF), with cmap format 12?

It seems fonttosfnt is limited to only Unicode Basic Multilingual Plane
characters (U+0000 to U+FFFF), with format 4, in the current implementation:

https://gitlab.freedesktop.org/xorg/app/fonttosfnt/-/blob/54fc73eeb8a2da16a49ab751d54d53dc2d693228/write.c#L872

https://learn.microsoft.com/en-us/typography/opentype/spec/cmap#format-4-segment-mapping-to-delta-values

The symbols for legacy computing is a Unicode 13.0 block in the range
U+1FB00..U+1FBFF (256 code points)

https://en.wikipedia.org/wiki/Symbols_for_Legacy_Computing

that is of interest for bitmap font (BDF to OTF) conversions. :)

All the best,
Fredrik