Re: Merging TTF files?

[Antoine Leca]

Terry Hancock wrote:
> 
> I've started using Yudit, which is nice Unicode editor,
> and I've run across the problem of adequate font coverage.
> 
> It seems there are a lot of TrueType fonts in the world,
> but very few which are reasonably complete (or at least
> have the glyphs I wanted). 

This is as expected.
No font designer is knowledgeable in _all_ scripts.
Furthermore there are complex interactions between scripts
(for example, it is difficult to design a font that looks
nicely in Latin, Devanagari and Hebrew, because the contrast
traditionnaly differ).

> An obviously desireable solution would be to find all
> the appropriate fonts and use them together

Correct. This solution is usually known as "virtual font".

> -- i.e. look up a "Zapf Dingbats" and
> a "Math Operators" font and combine them with the
> "Cyberbit" or other large Unicode font.

Doing a "real" merge so will infringe the copyright of the
designer (both in law and in intend), so I cannot recommand
that. OTOH, doing the merging with pure software (as it is
done in recent browsers, or with projects like Omega) is OK.


> Since Yudit uses FreeType as the font server I assume
> that any limitations it has in this regard are probably
> inherent in FreeType (which is why I'm writing here).

You are correct that FreeType currently lack the feature
of virtualization, which conceptualy stands one level higher
than the one FreeType intends to target.

Perhaps another feature for FTL ?


> 1) Load more than one TrueType font at a time -- i.e.
> overload them successively, leaving unassigned characters
> as they were?

That is a framework of a possible solution. I shall let
David T. or Werner comment on this.

This certainly goes quite beyond what is currently
implementated, so this is not straightforward. However,
I do not know enough of the internals of FT2 to know
if it is easy or not.

 
> 2) Create a TrueType font merge utility (using the
> FreeType library) to compose the fonts beforehand?

As I wrote, this is not advisable. Furthermore, in the
case of trueType, this is not technically feasible if
you want to preserve hinting: hinting relies on shared
tables (cvt, prep anf fpgm) that are *not* common to
two fonts. And merging these tables is quite a big
job that needs an entire decompilation of the hints and
the complete rewriting of at least the hints of the
"added" glyphs; this is much too much of a job.

Furthermore all this stuff does not pertain to the
objectives of FreeType.
 

> Also, it might be necessary to modify the code mappings,
> since a lot of TrueType fonts available on the web (Dingbats,
> for example) are not properly mapped for Unicode use).

Well, this is completely different. This one is quite easy
to write (just a mapping table that interacts with the
returned value of FT_Get_Char_Index). However, the table
would be specific to a particular font (while I agree
that Microsoft Dingbats is common enough to justify the
production of such a table). However, this is an issue with
text layout that Freetype does not intend to handle.

Yet another feature for FTL ?


Antoine