Comment # 28 on bug 897284 from Johannes Meixner

Regarding comment#26 where Karl Berry wrote:

"the only robust fix is to generate eps files
 that do have the necessary fonts embedded"

I do not agree.

Reasoning (as far as I understand it and regardless that I am
not at all a font expert):

Assume inner.eps has its needed font "SomeFont" included.

Assume outer.ps also needs the font "SomeFont" but has
only a subset of that font included.

According to what Chris Liddell explained in
http://bugs.ghostscript.com/show_bug.cgi?id=695508#c3
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there is already a font called "..." in memory, which
(as per the PS spec) we then use
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when inner.eps gets included in outer.ps to make a document.ps
then the subset of the font called "SomeFont" from outer.ps
is also used "(as per the PS spec)" for inner.eps.

Conclusion:
It does not change anything when inner.eps has its needed font
included if outer.ps has only a subset of the same font included.

Therefore (as far as I understand it and regardless that I am
not at all a font expert) the only robust solution is when
an application that includes only a subset of a font,
then that application must use its own application-specific
artificial name for its own application-specific subset-font.

In the above inner.eps / outer.ps example the solution would be:

Assume inner.eps has its needed font "SomeFont" (completely) included.

Assume outer.ps also needs the font "SomeFont" but has
only a subset of that font included and therefore it has
its particular subset included under the name "MySubsetOfSomeFont".

Then a PostScript interpreter would incude both fonts:
"MySubsetOfSomeFont" and "SomeFont" and everything could "just work".

See what Chris Liddell explained in
http://bugs.ghostscript.com/show_bug.cgi?id=695508#c3
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request that the app that emitted the PS file (apparently dvips)
use a subset prefix on the font name when embedding (that prefixes
the font name with a six letter (and "+") randomly generated
sequence - for example, our own ps2write device uses a hashing
algorithm to produce a subset prefixed name of "/EFSMOM+StandardSymL"
for the embedded version of StandardSymL. It would be worth raising
that anyway, as it's bad practice not to.
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