Re: Arabic letters separated by markup

From: John Hudson (
Date: Mon Jun 13 2005 - 21:55:49 CDT

  • Next message: Erik van der Poel: "Re: Arabic letters separated by markup"

    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
    Vancouver, BC
    Currently reading:
    Truth and tolerance, by Benedict XVI, Cardinal Ratzinger as was
    War (revised edition), by Gwynne Dyer

    This archive was generated by hypermail 2.1.5 : Mon Jun 13 2005 - 21:56:52 CDT