Implement new variation selector sequences for math script style variants

[tiroj]

Definition of variation selector sequences for math chancery/roundhand uppercase letters have been approved for Unicode 14, to be published in September. These can be implemented in the STIX Two Math format 14 cmap subtable.

[tiroj]

Unicode 14.0 defines new standardised variation selector sequences for chancery vs roundhand script styles of math alphabetics, but only for uppercase letters and only in regular weight:

# Mathematical alphabet script variants

1D49C FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL A
212C FE00;  chancery style; #  SCRIPT CAPITAL B
1D49E FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL C
1D49F FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL D
2130 FE00;  chancery style; #  SCRIPT CAPITAL E
2131 FE00;  chancery style; #  SCRIPT CAPITAL F
1D4A2 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL G
210B FE00;  chancery style; #  SCRIPT CAPITAL H
2110 FE00;  chancery style; #  SCRIPT CAPITAL I
1D4A5 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL J
1D4A6 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL K
2112 FE00;  chancery style; #  SCRIPT CAPITAL L
2133 FE00;  chancery style; #  SCRIPT CAPITAL M
1D4A9 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL N
1D4AA FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL O
1D4AB FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL P
1D4AC FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL Q
211B FE00;  chancery style; #  SCRIPT CAPITAL R
1D4AE FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL S
1D4AF FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL T
1D4B0 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL U
1D4B1 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL V
1D4B2 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL W
1D4B3 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL X
1D4B4 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL Y
1D4B5 FE00; chancery style; #  MATHEMATICAL SCRIPT CAPITAL Z

1D49C FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL A
212C FE01;  roundhand style; #  SCRIPT CAPITAL B
1D49E FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL C
1D49F FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL D
2130 FE01;  roundhand style; #  SCRIPT CAPITAL E
2131 FE01;  roundhand style; #  SCRIPT CAPITAL F
1D4A2 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL G
210B FE01;  roundhand style; #  SCRIPT CAPITAL H
2110 FE01;  roundhand style; #  SCRIPT CAPITAL I
1D4A5 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL J
1D4A6 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL K
2112 FE01;  roundhand style; #  SCRIPT CAPITAL L
2133 FE01;  roundhand style; #  SCRIPT CAPITAL M
1D4A9 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL N
1D4AA FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL O
1D4AB FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL P
1D4AC FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL Q
211B FE01;  roundhand style; #  SCRIPT CAPITAL R
1D4AE FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL S
1D4AF FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL T
1D4B0 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL U
1D4B1 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL V
1D4B2 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL W
1D4B3 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL X
1D4B4 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL Y
1D4B5 FE01; roundhand style; #  MATHEMATICAL SCRIPT CAPITAL Z

For 2.20, the second (roundhand) set of these has been added to the format 14 cmap subtable. The chancery set of variation selector sequences is not needed in the STIX Two Math font because the chancery forms are default. [Note: if someone were to fork the STIX Two Math font to make a version in which the roundhand forms were default, it would be necessary to update the format 14 cmap subtable accordingly.]

The roundhand script style glyphs—including the lowercase and the bold style—are still also mapped in the Stylistic Set ss01 feature, as in v2.10

[tiroj]

Updated sources and fonts delivered to STI Pub for testing. Issue reopened pending public release.

[Firestar-Reimu]

does this means that we can use \mathcal and \mathscr in parallel without using stylistic sets?