Re: [css3-fonts] unicode-range and unicode normalization

On 07/12/2010 08:06 PM, John Daggett wrote:
> fantasai wrote:
>
>>   * The UA must choose a single font for each grapheme cluster. [UAX10]
>
> Did you mean to refer to UAX10?  UAX10 is the Unicode Collation
> Algorithm and deals with how to compare two Unicode strings. Matching
> character streams to font character maps is a different problem, since
> the goal is not to determine equivalence but rather to render a
> character sequence correctly.

No, I meant [UAX29]. :) Sorry.

>> A related topic would be what happens when the base character is in
>> one element, the combining character in another, and the two are
>> assigned different fonts. Do we want different behavior for that
>> than for assigning different fonts through unicode-range?
>
> This starts to push into the realm of saving users from themselves. In
> general, I don't think we should burden implementations with complex
> error handling requirements like this unless it's really a common
> occurrence that's hard for the author to work around.  Codepoints
> defined in unicode-range descriptors act as a filter on the codepoints
> in the cmap of a font, I don't think we should blur that based on
> complex conditions.

I don't mind much what we do here, and am happy to leave it undefined
if that's easier. (I can see use cases for wanting part of a grapheme
cluster in a different color, which, depending on the font, may or may
not be possible--but not for having part of it in a different font.)

~fantasai