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

[Yao Zhang <yaoz vidar niaaa nih gov>]

Keith Packard wrote:

> > Can't you use coverage to determine this?

> Not easily.  Traditional Chinese, simplified Chinese, Japanese and Korean
> fonts cover the same Unicode regions, and fonts for all of these languages
> generally cover only a fraction of the total space making any coverage 
> based language tag only a guess at best.  In particular, we'd need to call 
> upon an expert in the area of the two Chinese variants to get an idea if 
> there were any codepoints distinguishing the two.

A little bit background of Chinese characters (Hanzi): Most of the
characters are not simplified, that is why the so called traditional
Chinese SET and simplified Chinese SET have lots of characters in common. 
In Unicode, all three forms of Chinese characters are there: unchanged,
traditional, simplified and they occupy different code point.  It is not
very difficult to distinguish the two SETs.

Since I am a fun of Chinese fonts, I have a large collection.  All those
Chinese fonts (PCF and TTF) I've seen can be categorized as:

1.  Covers only GB2312-1980: unchanged + simplified Chinese;
2.  Covers only GB12345-1990: unchanged + traditional Chinese;
3.  Covers only BIG5: unchanged + traditional Chinese;
4.  Covers Unicode CJK Unified Ideographs: unchanged + traditional + simplified
    Chinese;
5.  Covers Unicode CJK Unified Ideographs and its extension A.

You don't need to worry about #2 because the fonts in that category
always don't have Unicode cmap and Xft can not deal with it anyway.