[Fontconfig] Request for implementing font substitution for CJK fonts

[Akira TAGOH]

On Thu, May 31, 2012 at 8:19 PM, BlissSam <m13253 at hotmail.com> wrote:
> I think a tool to generate these kind of rules is necessary. However, the table I listed in the previous message is necessary, too.Try to think, if Helvetica font is required but not installed, fonconfig will surely choose Arial or Liberation Sans to substitute.As the same, if a document requires STSong, will fontconfig choose SimSun to display that document?These fonts are basic fonts in CJK typography, so I think substitutions among these fonts are necessary.
> Therefore, if Helvetica->Arial exists, STSong->SimSun exists too.

Well, strictly speaking there are no alternatives fonts of Helvetica,
Courier and Times for CJK fonts since those aren't designed for them.
we just fall back to anything else only when requesting those fonts
for glyphs in CJK. in your example, you may expect to modify
30-metric-aliases.conf, but for the above reason, I'm afraid I disgree
with it.
Aside from that, I suppose what you are linking to them is came from
the generic family names as we sometimes try to find the fallback
fonts out for them. e.g. Helvetica->sans-serif, Times->serif and
Courier->monospace. I mean, that would be the same case with assigning
the generic family names to fonts. so I would recommend to have the
better rules with the font author or the distros.

Honestly I would rather want to get rid of even them from fontconfig
tree in the future. the classification can be guessed from  the panose
and the OS2 table. the last piece that is missing in this idea would
be how to determine the order of the fonts though, it can be exported
outside fontconfig as the preference. that should provides the minimal
requirements. the problem on this idea is, there are no way to guess
the classification for non OpenType/TrueType fonts. I have no idea
when I can move on. but anyway.

Anyway, IMHO sort of the order of the fonts should be outsourced to
the desktop preference say. I guess it's not something maintained in
fontconfig today. if we don't have sufficient facilities to do so, we
should spend a time to implement it instead. that somewhat sounds
constructive and productive.

-- 
Akira TAGOH