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notofonts / tibetan

Noto Tibetan
SIL Open Font License 1.1
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`uni0F4A0FB70FB1` has misplaced anchor points and is vertically compressed #44

Open dscorbett opened 2 years ago

dscorbett commented 2 years ago

Font

NotoSerifTibetan-Regular.otf

Where the font came from, and when

Site: https://github.com/notofonts/tibetan/releases/tag/NotoSerifTibetan-v2.103 Date: 2022-09-20

Font version

Version 2.103

Issue

uni0F4A0FB70FB1 has misplaced anchor points and is too vertically compressed.

4 was fixed by deleting the bottom A component of uni0F4A0FB70FB1 and raising the below-base anchor points by 160 units. However, the below-base anchor points were positioned appropriately for A; with it removed, the bottom component is ya, which has a different shape from A, so the anchor points need repositioning.

In this font, there are some pairs of glyphs where one is a stack and the other is that stack plus A, e.g. uni0F4A0FA10FB1 and uni0F4A0FA10FB10F71. The latter is vertically compressed relative to the former to make space for the extra component. The glyph uni0F4A0FB70FB1 in previous versions was designed to include A and was therefore compressed; the glyph without A should be less compressed.

Fixing #4 is therefore not as simple as deleting the A. I recommend restoring the old glyph and mapping it to <U+0F4A, U+0FB7, U+0FB1, U+0F71>. If there should also be a glyph for <U+0F4A, U+0FB7, U+0FB1>, it needs drawing separately.

Character data

ཊྷྱཱ U+0F4A TIBETAN LETTER TTA U+0FB7 TIBETAN SUBJOINED LETTER HA U+0FB1 TIBETAN SUBJOINED LETTER YA U+0F71 TIBETAN VOWEL SIGN AA

Example of compression (not a bug, just for reference): ཊྡྱཊྡྱཱ U+0F4A TIBETAN LETTER TTA U+0FA1 TIBETAN SUBJOINED LETTER DA U+0FB1 TIBETAN SUBJOINED LETTER YA U+0F4A TIBETAN LETTER TTA U+0FA1 TIBETAN SUBJOINED LETTER DA U+0FB1 TIBETAN SUBJOINED LETTER YA U+0F71 TIBETAN VOWEL SIGN AA

Screenshots

ཊྷྱཱ

Example of compression (not a bug, just for reference): ཊྡྱཊྡྱཱ

simoncozens commented 2 years ago

Thanks. I have to admit, I don't really understand what's going on with the layout on this font. It doesn't help that there are comments referring to all the conjuncts as "legacy". Maybe it would be better to get rid of all conjuncts and just stack appropriately-compressed forms of each glyph, but I don't know the script well enough to know if that's acceptable. I needs... I don't really know what it needs. That's why I tried to fix what I thought was an easy-enough bug, and then re-released with all remaining issues outstanding.

I'll try and get some advice.