[pdftex] Character protruding error by font expasion

[Nagy Bence]

Dear all,

I tried to make a sample document for an article about composing engines
(include QuarkXPress, InDesign and pdfTeX) to Magyar Grafika [Hungarian
Graphic], and I ran into an interesting error in pdfTeX: marginal
kerning disappears by some expanded fontvariations.

I followed the Thanh's settings under plainTeX and the latest
pdfTeX-beta (but 1.11b make the same):

\font\Main=minion at 10pt
\rpcode\Main`\-=200
\resetefcode\Main
\pdffontexpand\Main 30 30 5
\pdfadjustspacing=2
\pdfprotrudechars=2
\Main

The missed fonts for different expansion settings (by the two page
long sample document):

\pdffontexpand\Main  5  5  5 -> none
\pdffontexpand\Main 10 10  5 -> none
\pdffontexpand\Main 15 15  5 -> minion-10
\pdffontexpand\Main 20 20  5 -> minion-15
\pdffontexpand\Main 25 25  5 -> minion-15
\pdffontexpand\Main 30 30  5 -> minion+25
\pdffontexpand\Main 35 35  5 -> none
\pdffontexpand\Main 40 40  5 -> minion-25

\pdffontexpand\Main 10 10 10 -> none
\pdffontexpand\Main 20 20 10 -> none
\pdffontexpand\Main 30 30 10 -> none
\pdffontexpand\Main 40 40 10 -> none

\pdffontexpand\Main 20 20 20 -> none
\pdffontexpand\Main 40 40 20 -> none

I think there is no relationship between the values, but the error
occurs only by the expansions with step value 5. I tried with
different font (clearface), this fails too.

I uploaded a sample into http://www.freeweb.hu/gimb/files/mgtest1.pdf,
everybody can see the error on the page 2 row 8. What's wrong then?

Greetings,

Bence