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Re: ligature formation across text chunks

From: Cameron McCormack <cam@mcc.id.au>
Date: Fri, 13 May 2011 15:56:07 +1200
To: Vincent Hardy <vhardy@adobe.com>
Cc: "public-svg-wg@w3.org" <public-svg-wg@w3.org>
Message-ID: <20110513035607.GJ5029@wok.mcc.id.au>
Vincent Hardy:
> (disclaimer: I had a bit of a long day, so I may not be processing
> this clearly enough :-)
>
> If I read the paragraph you quote and apply it to the example:
>
> a. the "f" and "i" characters map to a single 'fi' glyph (assuming the
>    font has a ligature for the "f" + "i" character sequence). So
>    characters at index i = 0 and i+1 = 1 map to a single glyph.
> b. for i = 0, we should apply the x value at index 0, i.e., 10.
> c. for i=1, we should ignore the value x, y and rotate, i.e., 20 is
>    ignored.
>
> So I would say that the spec. says that in this case, the second x
> value is ignored. In implementation work I did (ok, that dates back a
> bit :-), I am pretty sure that is how I interpreted this.

I neglected to quote from the spec about text chunks:

  An absolute position adjustment occurs in the following circumstances:
    * At the start of a ‘text’ element
    * At the start of each ‘textPath’ element
    * For each character within a ‘text’, ‘tspan’, ‘tref’ and ‘altGlyph’
      element which has an ‘x’ or ‘y’ attribute value assigned to it
      explicitly
  ...
  Each absolute position adjustment defines a new text chunk. Absolute
  position adjustments impact text layout in the following ways:
    * Ligatures only occur when a set of characters which might map to a
      ligature are all in the same text chunk.

So my thought is that the ligature can never be formed in the first
place, because the two characters are in different text chunks.

-- 
Cameron McCormack ≝ http://mcc.id.au/
Received on Friday, 13 May 2011 03:56:47 GMT

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