[Webkit-unassigned] [Bug 27413] New: Built-up (vulgar) fractions using the Unicode fraction slash (or other methods) not supported

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=27413

           Summary: Built-up (vulgar) fractions using the Unicode fraction
                    slash (or other methods) not supported
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: Text
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: pub-macosforge at coq.no


Unicode contains only a handful of precomposed vulgar fractions (viz, ½; ⅓, ⅔;
¼, ¾; ⅕, ⅖, ⅗, ⅘; ⅙, ⅚; ⅛, ⅜, ⅝, ⅞). In particular, 16ths and 32nds, which are
frequently used with imperial units, are not included.

The preferred solution, as suggested in an e-mail [1] sent to the WhatWG
mailing list, would be to let a sequence of one or more digits 0--9 followed
by a fraction slash [U+2044] followed by one or more digits 0--9 be rendered
as a built-up fraction. This behaviour is defined in Unicode, and Unicode
Technical
Report No. 20 explicitly says that this solution is appropriate for use in
mark-up
languages and not only in plain text.

Ideally, digits specifically designed for use in built-up fractions should be
used when available in the font used. Otherwise, scaling normal digits to 60%
height and 65% width, as suggested in the PostScript Language Cookbook,
would seem to be appropriate as fall-back.

It should also be noted that MathML does not seem to support vulgar fractions
at all, neither as specified nor as implemented in (other) browsers.

The correct behaviour is specified in Unicode 5.0, Chapter 6 `Punctuation' [2],
Section 6.1 `General Punctuation', heading `General Punctuation:
U+2000--U+206F', subheading `Other Punctuation',  subsubheading `Fraction
Slash' (p. 154):

“Fraction Slash.

“U+2044 FRACTION SLASH is used between digits to form numeric fractions, such
as 2/3, 3/9, and so on. The standard form of a fraction built using the
fraction slash is defined as follows: Any sequence of one or more decimal
digits, followed by the fraction slash, followed by any sequence of one or more
decimal digits. Such a fraction should be displayed as a unit, such as ¾ or
$\frac34$ [vertical built-up fraction]. The precise choice of display can
depend upon additional formatting information.

“If the displaying software is incapable of mapping the fraction to a unit,
then it can also be displayed as a simple linear sequence as a fallback (for
example, 3/4). If the fraction is to be separated from a previous number, then
a space can be used, choosing the appropriate width (normal, thin, zero width,
and so on). For example, 1 + ZERO WIDTH SPACE + 3 + FRACTION SLASH + 4 is
displayed as 1¾.”

[1]
<http://lists.whatwg.org/pipermail/whatwg-whatwg.org/2009-April/019340.html>
[2] <http://unicode.org/book/ch06.pdf>

This bug is also reported elsewhere as
<https://bugzilla.mozilla.org/show_bug.cgi?id=500293>.

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