#583 kept ligatures within +-50/1000 em. Adobe's composers are described
as dropping them past about -8% and +22% of the word space (John Hudson,
www-style, 2012-07): about -20 and +55 for a typical 250/1000 em space.
Condensed type shows a fixed ligature sooner than expanded type does.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Only real letterspacing (|tracking| > LIGATURE_TRACKING_LIMIT = 50/1000 em)
drops standard ligatures now, and an explicit liga/clig in the character's
features always wins. The OpenType panel's hint follows the same rule.
Builds on the vertical type from #145 (same data, commands and tools).
- Kinsoku (the strict set, horizontal Japanese too): no line starts with a
closing bracket, 、。, a middle dot, colon, !?, the long vowel mark,
iteration marks or small kana; no line ends with an opening bracket.
Hyphenation breaks obey it too.
- Tate-chu-yoko: a run of two or three half-width digits (10月, 第100回)
stands upright across the column as one block one em long, squeezed to
the em when wider; longer numbers stay on their side.
- Upright or on its side by Unicode's Vertical_Orientation: CJK and
symbols upright, marks that need a vertical form on their side when the
font has none; upright glyphs advance at least one em, centred, and turn
about the ideographic em box centre so they sit on the column's centre
line. Point type keeps its anchor on the first column's centre line.
- `vrt2` is no longer requested: its glyphs are already on their side, so
with the layout turning Latin and digits too they came out upside down
(and tate-chu-yoko blocks broke) in fonts that have it, e.g. Hiragino.
- The line→text mapping is one affine (`TextLayout::line_xf`, an exact
quarter turn plus the point-type offset); `logical_point` and
`physical_point` use it. Pixel snapping skips vertical type.
- Tests: kinsoku in both directions, tate-chu-yoko blocks, upright vs
sideways, anchor on the centre line, arrows along columns.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
