From: Peter Kirk (peterkirk@qaya.org)
Date: Sun Dec 07 2003 - 14:11:48 EST
On 07/12/2003 02:40, Philippe Verdy wrote:
> ...
>
>Just one example, suppose that you want to color the circumflex above
>a lowercase i or above a uppercase A: the base letters have distinct
>widths (meaning that the diacritic has a different horizontal position),
>distinct height (meaning that the diacritic has a different vertical
>position), and a distinct contextual effect on its base letter (the
>base lowercase i should have its dot removed)...
>
>
And what if you want to colour just the dot on i? Or just the crossbar
on a t? I ask this not to mock what you want to do but to point out that
the whole issue is rather tricky.
For solving issues like this, we need to distinguish carefully between
the markup level (Philippe's concern, it seems) and the rendering level
(John's concern). The markup needs to find a way to represent this kind
of separate formatting (and what about other changes - bold, italic,
size changes, even a different font face?) without using problematic
Unicode sequences. Fonts may have to deal with many tricky issues to
support this. Technically both of these are outside the scope of
Unicode, but Unicode may be called on to provide the glue by which they
can hold together.
A very tentative suggestion for some glue: a character which can take
combining marks but whose function is to throw those marks back on to
the preceding base character, preceding any markup. This would have to
be a zero width base character, not a format character or a combining
mark to avoid defective sequences; it would also have to be default
ignorable. Or maybe there is an existing character which can be reused
e.g. WJ (same counterarguments as recently on the bidi list of course).
A very simple implementation could use the backspacing trick Philippe
used to position the diacritics roughly. A more adequate one would be a
difficult problem for font developers, but one that is soluble in principle.
-- Peter Kirk peter@qaya.org (personal) peterkirk@qaya.org (work) http://www.qaya.org/
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