UTR #50 Review Memo

This page is a memo page to make our discussion on UTR #50 smooth.

Open Issues

Analysis by Codepoint

Two modes are presented: Stacked (text-orientation: upright) and Mixed (text-orientation: mixed). Codes used for analysis by codepoint:

UUpright; translates between horizontal and vertical
RSideways; rotates between horizontal and vertical
TUTypeset upright with alternate glyph. Best fallback is just upright.
TRTypeset upright with alternate glyph. Best fallback is just sideways.
VUpright wrt Unicode code charts, but translates between horizontal and vertical (VO=U/HO=L)

Codepoint classifications and notes by general category:

Potential tailoring categories:

  • Math relational operators (equals, greater-than, etc)
  • SB brackets


Notes on Interaction with Font Design

  • From what I understand, T allows anything; from changing glyph to changing orientations, so although “representative glyphs” are shown, their orientations are undefined in UTR #50. Some rotate, some do not, and it's up to font designer. Is this correct understanding?
  • If UTR #50 means fonts should not change glyphs/positions for U/S/SB, there are compatibility and font designing problems here.
    • Some fonts use different glyphs for parenthesis/brackets in vertical flow; e.g., U+FF62/FF63. kodomonoji_20111005-en.png
    • Some fonts use U+301D/301F glyphs for U+201C/201D in vertical flow.
    • Some fonts use GPOS to adjust positions of punctuation in vertical flow.
    • For brush-stroke fonts, start and end edges of strokes (起筆/収筆 in Japanese) vary by flow direction for several glyphs, just like it does for U+30FC, because the direction brush moves is different; e.g., suzuedo.png
  • Issues with non-square fonts:
    • U does not work with proportional or non-square fonts. If a font is condensed (tall) in horizontal flow, it needs to be condensed (wide) in vertical flow; e.g., AXIS fonts
    • S/SB does not work with slanted fonts; e.g., susha.png
  • Does the baseline alignment work good by just rotation?
    • EM DASH, Arrows, etc. aligns at center baseline?
    • Most font designers I contacted believe that it's ok as long as the font is a square font, but I'm worried as it has never been tested at all.

Potential Tailorings

  • upright-cyrillic
  • upright-greek
  • upright-latin
  • upright-letterlike
  • sideways-symbols
  • upright-math
  • upright-numeric
  • sideways-unified-punctuation-type-stuff?


spec/utr50.txt · Last modified: 2014/12/09 15:48 (external edit)
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