alonso.torres b053ac8751 🐛 Set digits tate-chu-yoko upright and centred in vertical text
Four fixes to how `digits` tate-chu-yoko composites lay out in vertical
text:

- A lone digit combines too, as CSS `digits <n>` combines runs of n or
  fewer, so it stands upright instead of turning sideways. The renderer
  (`split_digit_runs`) and the export path (`digit-combine-segments`)
  share the rule.
- Composites centre on the OS/2 typographic metrics, like upright glyphs.
  The hhea ascent of CJK faces exceeds the em, which set digits about
  0.07em below the kanji beside them.
- Letter-spacing stays outside the composite, as in CSS. Counting the
  trailing spacing in its width moved the digits left by half of it.
- The regional Chinese profiles no longer add the Han/Western gap around
  a composite: it sets in one ideograph's cell, as JLREQ already does.

AI-assisted-by: claude-opus-5-5
2026-10-27 18:00:33 +01:00
..