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Re: [css3-fonts] Minor Confusions Part A

From: Chris Lilley <chris@w3.org>
Date: Mon, 4 Feb 2013 10:09:27 +0100
Message-ID: <89191244.20130204100927@w3.org>
To: "www-style@w3.org" <www-style@w3.org>
Hello fantasai,

Monday, February 4, 2013, 7:16:02 AM, you wrote:

>    # The use of combining diacritic marks creates many variations
>    # for an underlying letterform:

> I don't understand this point. The "a" is not varying underneath
> the diacritics. What did you mean here?

I  think  that  what  is meant is that a set of variations are derived
from  the  base  letterform and the combining diacritic. Whether these
are  seen  as  a  'letter  with  an accent' or 'a different letter' is
culturally dependent. Whether the glyph of the base lettterform is the
same  as  the  standalone  version  or  different, depends on the font
design.

Perhaps

The use of combining diacritic marks creates many variations
derived from an underlying letterform:

>    # If a document contains characters not supported by the
>    # character maps of explicitly specified fonts, a user agent
>    # may use a system font fallback procedure to locate an
>    # appropriate font that does.

> It took me several reads to understand what was going on in this
> sentence. Maybe replace "explicitly specified fonts" with
> "the CSS-specified fonts"?

But  the  generic  font  families are also CSS specified fonts, though
they  are  not explicitly specified. Really there are three sources of
fonts

- explicitly specified (i.e. named) fonts
- CSS generic font families
- any other font, as a last resort

This  sentence  seems to be distinguishing the third case from the two
preceding ones.

Perhaps

If  the  CSS-specified fonts (both explicitly named fonts, and the CSS
generic  font  families)  do  not  provide  glyphs  for  some  of  the
characters  in a document, a user agent may use a system font fallback
procedure to locate an appropriate font that does.

>    # Fallback can occur because fonts are not explicitly
>    # specified or because authors fail to explicitly
>    # indicate the encoding used by a document.

> Fonts are always explicitly specified, because 'font-family'
> always has a value, even if it's a generic family keyword.
> So I don't understand the first clause.

This  sentence  seems  to  distinguish  the  first  and second cases I
mentioned above.

> Also don't understand the second clause. In what cases does
> not explicitly indicating the document encoding trigger
> fallback?

I  didn't  understand that part either, mainly because determining the
encoding  of  a  document seems to belong to other specifications than
CSS.   And  in  general those specifications return some sort of value
for the document encoding, not 'unspecified'.







-- 
Best regards,
 Chris                            mailto:chris@w3.org
Received on Monday, 4 February 2013 09:09:26 GMT

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