Re: [css-text] I18N-ISSUE-313: Definition of grapheme clusters

On Fri, May 23, 2014 at 1:09 AM, Richard Ishida <ishida@w3.org> wrote:
>
>
> Another is a worry whether we can really effectively split the world into
> semantically-perceived and visually-perceived characters - especially given
> the 'etc' that appears in the definition where we list appropriate
> operations for each. For example, are we sure that first-letter operations
> require semantically- rather than visually-perceived characters in all
> cases?  Where does cursor movement fit here? etc.
> characters (eg. in the Thai case)?


The fundamental split, in my view, is between characters and glyphs. There
are operations that are best understood as working on clusters of
characters and there are operations that are best understood as working on
clusters of glyphs.

I would argue that cursor movement and line-breaking are character-level
operations, whereas first-letter operations and letter-spacing are
glyph-level operations.  For example, in Thai the boundary following a
first-letter or the boundary where letter-space is to be inserted sometimes
does not correspond to a boundary between characters.

James