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Re: ligature formation across text chunks

From: Doug Schepers <schepers@w3.org>
Date: Fri, 13 May 2011 15:11:59 -0400
Message-ID: <4DCD827F.6080207@w3.org>
To: public-svg-wg@w3.org
Hi, folks-

Just a reminder that we agree that that technical discussions like this 
should be done on the www-svg list.  Could you move it there?

Thanks-
-Doug

Cameron McCormack wrote (on 5/12/11 10:53 PM):
> The spec says that every x or y value on a<text>  element starts a new
> text chunk, and that ligatures do not get formed across text chunk
> boundaries.  However, in http://www.w3.org/TR/SVG/text.html#TSpanElement
> just below the attribute definitions, there is this text:
>
>    The following additional rules apply to attributes ‘x’, ‘y’, ‘dx’,
>    ‘dy’ and ‘rotate’ when they contain a list of numbers:
>      ...
>      * When multiple XML characters map to a single glyph (e.g., when a
>        ligature is used) - Suppose that the i-th and (i+1)-th XML
>        characters map to a single glyph. In this case, the i-th value for
>        the ‘x’, ‘y’, ‘dx’, ‘dy’ and ‘rotate’ attributes all apply when
>        rendering the glyph. The (i+1)-th values, however, for ‘x’, ‘y’
>        and ‘rotate’ are ignored (exception: the final ‘rotate’ value in
>        the list would still apply to subsequent characters), whereas the
>        ‘dx’ and ‘dy’ are applied to the subsequent XML character (i.e.,
>        the (i+2)-th character), if one exists, by translating the current
>        text position by the given amounts before rendering the first
>        glyph associated with that character.
>
> You can never have a multiple XML characters mapping to a single glyph
> when you have an x or y value specified for the second or subsequent XML
> characters, because it would cause the ligature not to be formed.
>
>    <text x="10 20">fi</text>
>
> Even with a font that would otherwise form a ligature here, the f should
> be painted at x = 10 and the i at x = 20.  I think the text quoted above
> is misleading, then.
>
> Can someone confirm my reading of the spec?
>

-- 
Regards-
-Doug Schepers
W3C Team Contact, SVG, WebApps, and Web Events WGs
Received on Friday, 13 May 2011 19:12:07 GMT

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