Re: Font lookup ranges [was Re: Notes on Pango Xft backend]

[Yao Zhang <yaoz vidar niaaa nih gov>]

>From keithp keithp com Thu May 30 13:28:11 2002

> Around 12 o'clock on May 30, Yao Zhang wrote:

> > From your coverage map, it is easy to tell which category the font is in.
> > But in my opinion, combining different Chinese fonts together to get
> > a bigger coverage is generally not a good idea.

> It's good to know we can intuit the language tag from the Unicode coverage,
> that will make using Type1 fonts (and others without OS/2 tables) easier.

I am still trying to understand what a language tag is.  If for a font,
it means the font is designed for one region, then we can say category
#1 and 2 is for zh_CN (mainland China) and probably zh_SG (Singapore), #3
is for zh_TW (Taiwan), zh_HK (Hong Kong) and zh_MO (Macau). I am not sure
about #4 and 5.  A font in category 4 or 5 could be for any of the above,
and even ja_JP or ko_KR?

For TTF font, there is another place to check: if it is designed for one
region, it tends to have localized name tables.  Or if the information
is hard to get/guess, just maintain a separator database somewhere.  It
is bad or even dangerous to make computer overly smart.

> Unifying fonts together to present a document works well when the selection
> of fonts match the selection of langauges; a document with english and
> traditional chinese sections should typeset the english sections in a
> western font and the chinese sections in an traditional chinese font.

Unifying a western font and a chinese font together is definitely
desirable.  Actually, I have seen lots of people asking for this feature.
While the current codepoint based font priority/fallback mechanism has
that illusion but unfortunately when applied to two Chinese fonts with
different coverage, it really looks bad.  Even worse, when several
CJK fonts are combined together, it looks ugly.  I would rather see
blank square.  What I am trying to say is there should be a limit when
using this mechanism to increase coverage.  I always heard people say
that they want to see English in this font, Chinese in that font, etc.
But never some Chinese in this font, other Chinese in that font - unless
they have explicitly specified for that and they want to have total
control of it, as in heading font, paragraph font, etc.

From: Owen Taylor <otaylor redhat com>

> The question being discussed here is not combining multiple fonts ... 
> Pango already does this; it's pretty much a requirement if you
> want to be able display multilingual text. (The alternative is
> that the document creator knows exactly what fonts the user
> has on their system and specifies those fonts.)

> The question is how to combine multiple fonts in a way that avoids
> the "mixed" appearance that you are seeing.

What I am trying to say is that the current implementation goes to
far to combine different Chinese fonts together or even different CJK
fonts together.  In my opinion, that is bad.  They could be in different
combined font, not in one combined font.

Regards,

Yao Zhang