Re: What's the relationship between vfs and tfms?

[Rebecca and Rowland <rebecca@astrid.u-net.com>]

>as berthold said, it's the 3 TFMs & 2 VFs for 3 founts scheme.

So it is - and thanks for this detailed explanation.

>1 base TFM : the 8r which gives access to all glyphs in the type 1
>fount, although to be effectively accessible, the type 1 fount will
>need to be reencoded by the driver before being downloaded.
>This is already a full functionnal TFM that allows typesetting in its
>own (ligatures & kerning are present).

I see.

>1 pair VF+TFM for each one of T1 (8t or 9e) and OT1 (7t or 9t) TeX
>encoding,

9e and 9t?  I've not heard of these encodings. Could someone give me a
pointer to some information on them?  I can't see anything obvious at CTAN.

> these being only virtual fonts refering to the base one.
>In 2 words, both TFM + VF are needed for them because TeX is happy
>(fooled ?) with one TFM, whatever it is related to (real or virtual
>or reencoded font), when you typset in free-KA using T1 encoding,

free-KA?  I *think* you mean `typeset using the fount family fka'?  Is that
right?

> tex
>will only need the metric information provided by fkar8t.tfm. The
>conversion virtual -> real is provided by the VF that is essentially a
>collection of fragments of DVI code drawing each individual (virtual)
>charachter with DVI opcodes (allowing rules, special, placement of
>charachters from some real font, offsets, etc.). Thus it is natural
>that the VF refers to the base TFM, and that the base TFM be used in
>order to read the metrics from the real font used.

Righto - this makes sense.

>Typically, when asked to deliver some glyphs from a given fount fkar8t,
>a driver will _first_ look for the file fkar8t.vf and desassemble it
[snip]
>will be automagically auti-hinted in fontlab--the usual stuff in one
>word).

Okay - got this too.

[snip]

>Hope i helped.

You certainly have - thank you very much.

Maybe I'm being stupid, but I still don't see why vftovp reads two tfms and
a vf when re-creating a vpl.  What is it that lives in a vpl file?

Thanks again,
Rowland.