Japanese layout measures leading from the top of one line's ideographic
em box to the next (the right side, in vertical type), not from baseline
to baseline. The Paragraph panel menu now offers both:
- `ParaStyle.leading_model`: RomanBaseline (as before, the default) or
EmBoxTop. With EmBoxTop a line's leading is the space below it — the
next line's em box top is this line's plus its leading, and the next
baseline hangs from there by that line's tallest em box — and area
type's first line touches the top of the frame (its em box top on the
frame's top, at least Area Type Options' minimum). With baseline
leading a line's leading stays the space above it.
- Lines of one size are exactly as far apart either way; the models
differ for mixed sizes and for the first line of area type (fonts
whose ascent isn't the em box top: Hiragino's nearly is).
- The em box top comes from the font's vertical metrics (#343), else
0.88 em. Written only when EmBoxTop.
- `text.setFormat {leadingModel: "romanBaseline"|"emBoxTop"}`; menu items
Top-to-Top Leading / Bottom-to-Bottom Leading (checked as set); catalog
rows in ja and zh-hant.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
imachusandClaude Opus 5.5
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