Mixed Fonts are real fonts - comments?

I have idea of making mixed fonts accessible to all apps, at the same
level as fontconfig...comments welcome...


If the goal is to build up a Unicode font which contains most of the
currently used worlds scripts, there are two approaches -
    - Mixing
    - Growing

The free font project uses the second approach by slowly adding glyphs
for different languages to the FreeSans, FreeSerif and FreeMono fonts.

Mozilla browser takes the other approach of mixing and matching fonts on
a per language basis.  The user can configure a font for each of a list
of languages, and glyphs from multiple fonts are used.

These approaches both converge on the goal of having a set of useful
high quality fonts with consistent Look and Feel covering the most used
languages of the world.  The main difference is when, where and by whom
the glyphs are combined into the font package - late or early.

There has been good work done in centralising the management of
installed fonts.  Take for example fontconfig which uses a base xml file
/etc/fonts/font.conf which contains centralised list of font
directories, alias names, substitutions etc. FontConfig supplies a
unified API to get font lists and search for best matching fonts and more.

Ideally there should be a way to mix fonts by configuration at the level
of fontconfig and use them simply with no performance penalty, while
keeping them configurable ie.
- Complex mixed fonts can be configured by sub-font unicode ranges
- Mixed fonts are named like normal fonts and accessed via same API
- All applications reference mixed fonts simply by name [eg Mozilla]
- Automatic construction of the mixed font from its configuration
- Cacheing the mixed font for performance, if necessary
- Automatic rebuild when font configuration changes, if possible


This will allow programs like Mozilla to use fonts more simply, and the
font configuration to be centralised and reused desktop wide.  It
extends on the Mozilla approach as any range of glyphs are possible, not
just by language group.  It allows experimentation and adaption so good 
global Unicode fonts can emerge, later to be packaged as single fonts.