U+0615 ARABIC SMALL HIGH TAH is too low

[dscorbett]

Cascadia family version

2106.17

Cascadia family variant(s)

Cascadia Code (the version with ligatures), Cascadia Mono (the version without ligatures)

Font file format(s)

.ttf (variable), .ttf (static), .otf (static)

Platform

macOS 10.14.6

Other Software

No response

What happened?

The glyph assigned to U+0615 ARABIC SMALL HIGH TAH was not designed for U+0615. It was clearly designed to be a component of glyphs for characters like U+0768 ARABIC LETTER NOON WITH SMALL TAH, but when it is used as its own character, it is positioned too low.

It overlaps other above-base marks. For example, here it is with U+064B ARABIC FATHATAN:

It also overlaps tall letters like kaf and lam.

U+0615 is a Quranic annotation sign, and as such should be placed at a constant high height, even if the base is short. For example, it should be at the same height above alef and beh.

For comparison, here is the same string in Amiri:

For another comparison, here a similar string in Noto Sans Arabic (it shows U+06D6 instead of U+0615 but the idea is the same):

[aaronbell]

These particular use cases appear to be specific to Qur'anic typesetting, and as Cascadia Code is not intended for that purpose, it will not be supported at this time.

[dscorbett]

Why does Cascadia Code support U+0615 ARABIC SMALL HIGH TAH? Its only use is for Quranic typesetting.