Re: Math setup with Times (Termes)

[Hans Hagen <pragma@wxs.nl>]

Mojca Miklavec wrote:

> What are we talking about? Do you mean the old virtual fonts (.vf
> files) or mkiv's virtual fonts or something completely different?

What You Don't Want To Know:

a virtual font is just a regular font but has references to other fonts 
instead, like

char 1 -> font x, char 10 (or dvi commands instead)

and then it can has kerning etc within its own set

tex itself only sees characters as things with dimensions and a few 
properties and when typesetting the paragraph uses info from the font 
with respect to kerning and ligature building

now, traditional tex has only tfm files and when virtual fonts were 
introduced the engine was not adapted at all; so, a virtual font still 
has a tfm file (with characters etc)

however, when the font is being used in the backend, an extra lookup 
takes place and when a vf file is found, information from that file is 
used for embedding (in pdftex); of course dvi postprocessors also look 
at that file

so we have:

tfm      -> tfm used by frontend and backend
tfm + vf -> tfm used by frontend, vf used by backend

on top of that a map file will point from fontname to real name (pfb) 
and this is why in a map file you don't see the virtual font names at 
all, as it's the names inside the vf that matter

so say that we have:

a.tfm + a.vf

but internally

a.vf -> font b, c, d (or further chained)

then b, c, d need to be resolved to real names

as there is no checking going on and as the tfm file has no info about 
itself being virtual you can imagine that interesting side effects can 
take place when an old (unknown of) vf lays around ... it will kick in 
at backend time (this is why the texfont script does a clean up)

in luatex we have integrated these mechanisms, so internally a font can 
have virtual properties (a few more than original tex)

however, by default luatex acts like tex, so users won't notice; as 
luatex has the backend integrated, at some point it will need the vf and 
mkiv will happily fulfill that request

but ... and this is the catch ... in mkiv we use (1) opentype, (2) type 
1 and (3) traditional tex fonts

(1) is not related to virtual fonts but we can (and do) extend fonts 
internally using virtual technology

(2) in pdftex tfm/vf files are used but mkiv does not look at those 
files but uses afm files directly (right from the start)

(3) the only place in mkiv where tex metric files are still used is in 
math as we need the additional (math specific) info

as it makes no sense to keep supporting the old math fonts while open 
type variant sare under way, i decided to stick to unicode math and as a 
result we need to use virtual font technology to make that unicode variant

for the lm fonts, this is mostly done and as they have no virtual (vf 
based) fonts it's transparent

for tx/px however, as they use virtual fonts, it gets hairy what file to 
load; technically there is no obstacle but i've chosen to stay away from 
the tfm/vf mess and use just the natural tfm variants (i.e. the ones 
that match the pfb) and therefore we might need a few extra vectors (and 
maybe font files) in math-vfu that map to the right slots; using the 
vf's as well would complicate matters and it's not worth the trouble

so, what we need to do is to figure out teh few missing files/vectors, 
add them, and then let users fill in the gaps in vectors

are you still there?

Hans

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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
      tel: 038 477 53 69 | fax: 038 477 53 74 | www.pragma-ade.com
                                              | www.pragma-pod.nl
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