Re: Normalisation and font technology

From: John Hudson (
Date: Wed May 29 2002 - 15:57:30 EDT

At 12:42 5/29/2002, Aki Inoue wrote:

>As John mentioned, we're working on to add the character space processing
>capability to the OS. In fact, Cocoa framework, one of the two primary
>APIs in Mac OS X, can already handle most of the combining marks pretty
>reasonably well without the help from AAT tables.
>Please note neither glyph space only nor character space only solution
>cannot fully embrace the flexibility of Unicode. It needs to be
>hybrid. By being glyph space only solution, you lose the character
>semantics defined in Unicode in typesetting. Whereas, by being character
>space only solution (meaning applying NFC before rendering), you cannot
>render arbitrary sequences of composed characters allowed by Unicode.

Yes, I am aware of that and, if you read back a couple of days on the OT
list, you will see that I made a distinction between handling of those
characters with canonical composition/decomposition in Unicode and the
display of arbitrary, unanticipated and unencoded diacritic combinations
that, obviously, require glyph space processing.

>As the Cocoa framework currently does, you could position combining
>characters without precomposition by just looking at the combining class
>for most cases. However, it's still desirable fonts to have positioning
>information for better typographical result since the font designers
>themselves know best about glyphs they're designing.


It sounds as if you understand that the current glyph space only
implementation for resolving canonical composition/decompotion is a
problem, and that you are are working on a solution. Thank you. My main
concern was that someone might think that this is a reasonable model for
handling this, and it wasn't immediately clear that Apple did not consider
this, in fact, to be an appropriate long term solution.

John Hudson

Tiro Typeworks
Vancouver, BC

When the pages of books fall in fiery scraps
Onto smashed leaves and twisted metal,
The tree of good and evil is stripped bare.
                                        - Czeslaw Milosz

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