Re: Displaying Plane 1 characters (was Re: TV teletext)

From: David Goldsmith (
Date: Tue Oct 13 1998 - 17:47:56 EDT

Paul Keinanen ( wrote:

>What is the technical readines in different computer environments to display
>non-BMP characters ? The already overstretched cmap structure in True Type
>Fonts are limited to 16 bits. What is the situation with various Type x
>systems ?
>If Plane 1 is filling up at a fast rate, it would be nice to be able to
>enter and display these characters. If utilities that can handle also
>non-BMP characters become common, this will reduce the pressure to get new
>characters into the BMP. Currently, it would be rather pointless to assign
>some characters needed e.g. for terminal emulation to Plane 1, since they
>could not be displayed today.

Apple's ATSUI (Apple Type Services for Unicode Imaging) technology, part
of our soon-to-be-released Mac OS 8.5, is perfectly capable of handling
and displaying characters from outside Plane 1. It can use any
sfnt-format (TrueType or OpenType) font that has the appropriate
typographic tables (AAT == Apple Advanced Typography tables).

Basically, it handles surrogates as a form of ligature. The surrogates
are translated to dummy glyph IDs, and then the combination is handled
similarly to a ligature. ATSUI is fully aware of surrogates, however, and
will treat the combination as a single character; the ligature trick is
only a trick for rendering.

John Jenkins has a demonstration of Pollard encoded using surrogates,
which I showed in Tokyo at IUC 12, and I think John may have shown it at
IUC 13 (I wasn't there).

Mac OS 8.5 will also support direct input of Unicode into aware
applications by keyboards and input methods.

David Goldsmith
International and Text Department Architect
Apple Computer, Inc.

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