Re: using the SS (slanted symbol) font with gropdf

[Deri]

On Tuesday, 13 December 2022 20:26:53 GMT G. Branden Robinson wrote:
> Hi Deri,
> 
> At 2022-11-27T01:41:57+0000, Deri wrote:
> > I have looked at the SS font now.
> > 
> > It is not included in devpdf because symbolsl.pfa is not a type 1
> > postscript font! It is a postscript program which generates a font
> > when run by a postscript interpreter. The gropdf man page does say you
> > can only use it with type 1 fonts. If you view the file you will see
> > it is significantly different from other pfa files on your system.
> 
> Well, not _blatantly_...
> 
> $ head -n 1 /usr/share/a2ps/fonts/pcfont.pfa
> %!PS-AdobeFont-1.0  -*- PostScript -*-

Hi Branden,

That is a type 1 font.

> $ head -n 1 ./build/font/devps/symbolsl.pfa
> %!PS-Adobe-3.0 Resource-Font

And this is a type 3, a very different beast:-

https://www.prepressure.com/fonts/basics/type3

Which requires a postscript interpreter to parse it, as I said. 

> So I looked at a PFB file, too.
> 
> $ head -n 1 /usr/share/fonts/type1/gsfonts/n022023l.pfb | od -c
> 0000000 200 001 035 005  \0  \0   %   !   P   S   -   A   d   o   b   e
> 0000020   F   o   n   t   -   1   .   0   :       N   i   m   b   u   s
> 0000040   M   o   n   L   -   R   e   g   u   O   b   l   i       1   .
> 0000060   0   6  \n
> 0000063
> 
> $ file /usr/share/a2ps/fonts/pcfont.pfa
> /usr/share/a2ps/fonts/pcfont.pfa: PostScript Type 1 font text (-*-
> PostScript -*-)
> 
> $ file ./build/font/devps/symbolsl.pfa
> ./build/font/devps/symbolsl.pfa: PostScript Type 1 font text
> 
> $ file /usr/share/fonts/type1/gsfonts/n022023l.pfb
> /usr/share/fonts/type1/gsfonts/n022023l.pfb: PostScript Type 1 font program
> data
> 
> I don't think we should shell out from gropdf to run the file(1) command
> anyway, but...
> 
> Is "%!PS-AdobeFont-" a reliable indicator of acceptability to gropdf?

No.

Postscript fonts 0, 2, 4, 5, 32 and 42 are equally not allowed.

> > I don't think it is unreasonable for gropdf to barf over its contents,
> > and viewers to barf as well.
> 
> I agree.  If we can make gropdf barf on invalid input, we don't subject
> the PDF viewer to the indignity of playing centipede.[1]
> 
> > A reasonable error message when consuming a non type 1 file would be
> > desirable. :-)
> 
> Yes.  Happy to code one up and run it by you on this list if you can
> verify my surmise above, or offer a substitute.

It would be a warning only. The important thing is to avoid embedding the body 
of the font if it is not a type 1 font, to stop confusing the viewer, but 
leave the font stub the same as is done for non-embedded fonts. It is on my 
list, once committed, happy for you to adjust the precise wording of the 
warning.

Cheers

Deri

> Regards,
> Branden
> 
> [1] https://en.wikipedia.org/wiki/Centipede_(video_game) [2]
> [2] (Why, what did you _think_ I meant?)