Glyph overlap issue with USE

[khaledhosny]

Defect Report

Glyph overlap issue

The version of Noto Sans Sinhala from this repository have some glyph overlaps issue, compared to the version from https://fonts.google.com/noto/specimen/Noto+Sans+Sinhala when shaped with USE.

Font

NotoSansSinhala/unhinted/ttf/NotoSansSinhala-Regular.ttf

Where the font came from, and when

https://github.com/notofonts/sinhala/releases/tag/NotoSansSinhala-v2.005

Issue

With HarfBuzz >= 4.4.0 (where Sinhala is shaped through USE) and the font from the repo:

hb-view NotoSansSinhala/unhinted/variable-ttf/NotoSansSinhala\[wdth\,wght\].ttf "ශ්‍රී ලංකාවේ ප්‍රධාන ජාතිය"

Compared to the font from GF:

hb-view Noto_Sans_Sinhala/NotoSansSinhala-VariableFont_wdth\,wght.ttf"ශ්‍රී ලංකාවේ ප්‍රධාන ජාතිය"

DirectWrite output is similar to HarfBuzz in both cases.

[khaledhosny]

I found this while debugging harfbuzz/harfbuzz#3725

[simoncozens]

The obvious big-hammer fix would be to reclassify the spacing marks as bases, to stop the width zeroing. We really want to be able to support both USE and pre-USE shapers.

[simoncozens]

I've fixed this by making them all bases.