From: Michael Everson (everson@evertype.com)
Date: Wed Oct 26 2005 - 15:15:36 CST
At 00:51 +0400 2005-10-27, Andrew S wrote:
>1. Does the Unicode standard mandate that a compliant font which
>defines glyphs for both the character U+0031 (arabic numeral "1")
>and U+006C (lowercase Latin "l") define those glyphs to be not
>homographic, with "homographic" defined as "a human knowledgeable of
>arabic numerals and latin letters couldn't reasonably be expected to
>reliably distinguish the glyphs without the aid of context"?
No. Glyphs are informative and you can do what you want. You might
choose to give your users useful glyphs, but you needn't.
>2. Does Unicode allow a compliant font to define homographic glyphs
>for U+0041 (first letter of Latin alphabet) and U+0410 (first letter
>of Cyrillic alphabet)?
Yes. Glyphs are informative and you can do what you want. You might
choose to give your users useful glyphs, but you needn't.
>Does it allow the character U+0022 (double quote) to be homographic
>to the string U+0027 U+0027 (two single right quotes)?
Yes. Glyphs are informative and you can do what you want. You might
choose to give your users useful glyphs, but you needn't.
>3. If so, then where can I find the definition of the equivalence
>relation of permitted homographics, defined on the set of all
>Unicode character strings (including of course one-character
>strings)? Is confusables.txt supposed to be the definition of this
>relation?
Well, Unicode is not a legal codex, so relax, breathe deep, and
realize that human beings, who have been making marks on paper and
other media for millennia in order to communicate with one another,
are untidy creatures. .
>4. Is the equivalence relation of mandatory homographics empty?
No more so than this question.
>5. Besides inter-glyph homographic constraints, does Unicode define
>intra-glyph constraints for any characters?
No. Glyphs are informative and you can do what you want. You might
choose to give your users useful glyphs, but you needn't.
>For example, does Unicode contain any rules which would prevent a
>compliant font from defining the glyph for the character U+0041 to
>look like a Times New Roman "B", or the glyph for the character
>U+0042 to look like a smiley face?
No. Glyphs are informative and you can do what you want. You might
choose to give your users useful glyphs, but you needn't.
>I was under the impression that Unicode officially disclaims
>specification of glyphs and mappings between characters and glyphs,
>but the quote above seems to show that I was mistaken.
The quote is:
>"Not all sans-serif fonts allow an easy distinction between
>lowercase l, and uppercase I and not all monospaced (monowidth)
>fonts allow a distinction between the letter l and the digit one.
>Such fonts are not usable for mathematics. In Fraktur, the letters I
>and J in particular must be made distinguishable. Overburdened Black
>Letter forms are inappropriate. Similarly, the digit zero must be
>distinct from the uppercase letter O for all mathematical
>alphanumeric sets."
And clearly, the "must" refers only to the specific context of
mathematics and math fonts, where the shapes in question have
relevance.
-- Michael Everson * http://www.evertype.com
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