Re: [jlreq] Digital native version of JLReq, discuss goals and changes from the current version (#281)

I see several areas that could be expanded or added:

- The importance of type placement relative to the CJK embox -- how text object boundaries, line boxes, text run alignment, leading, white space around the text, etc all are conceived to be relative to the embox (type virtual body) rather than to the Latin baseline or other Latin metric (even though fonts are built using Latin metric-based tools, and digital rendering pipelines use the Latin baseline as the origin point). This means engines must introduce the embox concept throughout their implementation and switch between it and the Latin-based conventions when composing text using Japanese rules.
- The issue of how a given character's attributes or composition rules are governed not only by the Unicode code point, but also the font's implementation of features and glyph design to result in a final glyph. Perhaps a diagram would be helpful to show this.
- The basic mojikumi aki rules and classes were conceived in an age when production tooling used fixed widths for the characters and made adjustments to the spacing in fractional units of 1 em (e.g. 1/2 em aki). The normal width of the line would be in whole em units, and thus monospaced Japanese text would often fit perfectly, or be easily adjusted to fit perfectly. Modern-day fonts and typographic practice, however, has evolved to include proportional typography to be interspersed with monospaced Japanese text, and the old rules and conventions for adjusting spacing have remained unchanged, or have strayed into undefined behaviors. In text with lots of Latin script words, or even using proportional kana and punctuation glyphs, has introduced a situation where the old adjustment rules are overly strained to create the same neatly aligned text as before. In fact, such neat alignment may not even be desirable, yet we have no replacement for the basic mojikumi aki adjustment rules to serve these new use cases.
- Reflowable document creation is even more complex in that all the mojikumi aki spacing has to be expressed in ranges, the text object sizing may not be in even em units, the line breaking will be unpredictable, etc. We should state clearly which conventions from static document creation should be preserved (e.g. the embox-based measurements and dimensions) and which can be relaxed, so a natural hierarchy of rules and conventions can be understood.

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Received on Thursday, 5 August 2021 01:47:45 UTC