[pdftex] font strategy in pdftex

[Kuznetsov A,V.]

Dear pdftex developers,
I found excessive font embedding in documents
produced by pdftex.

I use 3 ways (dvips+distiller, dvipdfm, pdftex) to generate pdf
from the following file and font map.
%%%  FILE %%%%
        \def\test{abcdefghijklmnopqrstuvwxyz\\}
        \begin{document}
            \font\true=ptmr8r17 at 10 pt\selectfont\true\test
            \font\true=ptmr8r   at 10 pt\selectfont\true\test
            \font\true=ptmr8r9  at 10 pt\selectfont\true\test
            \font\true=ptmr8r8  at 10 pt\selectfont\true\test
            \font\true=ptmr8r7  at 10 pt\selectfont\true\test
            \font\true=ptmr8r6  at 10 pt\selectfont\true\test
            \font\true=ptmr8r5  at 10 pt\selectfont\true\test
        \end{document}
%%%  This is the map for pdftex, maps for dvips and dvipdfm are similar  %%%
        ptmr8r   Times-Roman   <8r.enc
        ptmr8r17 <tir_____.pfb <8r.enc ".97 ExtendFont"
        ptmr8r9  <tir_____.pfb <8r.enc "1.03 ExtendFont"
        ptmr8r8  <tir_____.pfb <8r.enc "1.07 ExtendFont"
        ptmr8r7  <tir_____.pfb <8r.enc "1.11 ExtendFont"
        ptmr8r6  <tir_____.pfb <8r.enc "1.15 ExtendFont"
        ptmr8r5  <tir_____.pfb <8r.enc "1.25 ExtendFont"
%%%%%%%%%%%%%%
As seen, only the standard font is used.

The results are dramatically different.
Neither dvipdfm nor dvips+distiller embed standard resource
but pdftex embeds it six times. Why? Only Tz operator should
change horizontal scaling when an extended font is used
(see 'PDF reference' sec.ed. 5.2.).

Excessive font embedding increases file size, for example,
 1.987 kB for dvips+distiller,
 3.990 kB for dvipdfm and
51.791 kB (!) for pdftex.
Moreover, such a font strategy leads to incorrect result.
Printer (or viewer) font will be used for unextended font
while creator's font is embedded for extended fonts. As it was
recently discussed in mail-list, these fonts can be different.

What is the reason for the excessive font embedding in pdftex?

A.Kuznetsov