From: John Hudson (tiro@tiro.com)
Date: Mon Jun 13 2005 - 21:55:49 CDT
Richard Wordingham wrote:
>> Do you know in what form this cursor positioning data is stored within
>> the font file? Is it basically an x-coordinate for where the cursor
>> should be positioned within the glyph?
> Yes and yes. However, it's in the GDEF table, not the GPOS table
> (faulty memory).
It would be more accurate to say that cursor positioning *can* be included in a font's
GDEF table, and an application *can* reference this information. I'm not aware of any
OpenType fonts that actually contain this information, nor of any applications that would
make use of it if it were included. To date, all applications I have looked at that
positiong the cursor within a ligature do so without reference to the GDEF table. If a
ligature has two component characters, they position the cursor halfway across the advance
width; if a ligature has three components, they positiong the cursors a third and then two
thirds of the way across the advance width, and so on. Cursor positioning information in
the GDEF table is a level of refinement of which, to date, neither fonts nor applications
are taking advantage.
There are numerous aspects of the OpenType font format specification that, though they
will be welcome when implemented, are not part of the current reality of text layout and
display. The justification table is another example.
John Hudson
-- Tiro Typeworks www.tiro.com Vancouver, BC tiro@tiro.com Currently reading: Truth and tolerance, by Benedict XVI, Cardinal Ratzinger as was War (revised edition), by Gwynne Dyer
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