Re: eqn formatting issues with grops and gropdf

[joerg van den hoff]

On 26.07.22 18:19, Deri wrote:
> On Tuesday, 26 July 2022 09:00:25 BST joerg van den hoff wrote:
> > me again with an update/correction to the previous description of the issue
> > (the described problem remains, though):
> >
> > 1.
> > regarding the symobl fonts used by grops and gropdf I previously stated the
> > former were using SS (symbols slanted) and the latter S (symbols) which I
> > presumed according to the looks of the greek letters in the ps output
> > (upright) and pdf output (slanted to the right like italics). this was
> > *wrong*. looking into the font information in the formatted files it was
> > the other way around (grops was using SS and gropdf using S).
> >
> > looking into the DESC files, I do find indeed entries
> >
> > grops:  fonts 9 0 0 0 0 0 SS S ZD ZDR
> > gropdf: fonts 9 0 0 0 0 0 0 S ZD ZDR
> >
> > which explains the font selection that occurred. I do not understand,
> > however, while this ultimately lead to _slanted_ glyphs with gropdf and
> > _upright_ glyphs with grops (exactly the other way around as I would have
> > expected for S vs SS).
> >
> > 2.
> > forcing grops to also use S (by editing the DESC file and removing SS from
> > the entry) leads to sane ps and pdf output with both devices (no
> > misalignment and strange irregular widths of the greek letters). so this
> > would be the quick patch to "repair" grops: change the DESC file.
> >
> > 3.
> > using now the same font S, the glyphs produced by grops are upright
> > (expected) and those produced by gropdf are slanted (unexpected). why is
> > that??
> >
> > the main observation remains unaltered: in standard setup grops uses SS for
> > typesetting greek letters since SS is found before S according to DESC and
> > this leads to rather massive typesetting errors in equations using possibly
> > many greek letters: cumulative mispositioning of stuff later on the same
> > line.
> >
> > what do to about this?
> >
> > thank you
> > joerg
>
> Hi Joerg,

hi deri,

> You are correct that gropdf does not include the SS font. The reason is because 
> it is not a proper
> font, it is instead a postscript program, which, when run by a postscript 
> interpreter such as
> ghostscript or a postscript printer, generates a slanted version of the symbol 
> font. This is not
> valid as a pdf font.

thanks for this clarification. I was not aware of this circumstance (SS not being a 
"real" font).

> The SS font and the S font both define *a but only S defines *A so when they 
> are both loaded
> with .special SS S the lower case is found in SS but uppercase in S. Since 
> gropdf does not have
> SS *a is found in S and a special command is sent to gropdf "x Slant 16" which 
> tells it to slant the
> glyph by 16 degrees.
>
> If you type:-
>
> echo "\[*a]" | groff -Z
>
> You will see:-
>
> x T ps
> x res 72000 1 1
> x init
> p1
> x font 11 S
> f11
> s10000
> V12000
> H72000
> md
> DFd
> C*a
> h6310
> n12000 0
> x trailer
> V792000
> x stop
>
> But if you type:-
>
> echo "\[*a]" | groff -Tpdf -Z
>
> It changes to:-
>
> x T pdf
> x res 72000 1 1
> x init
> p1
> x font 11 S
> f11
> s10000
> x Slant 16
> V12000
> H72000
> md
> DFd
> C*a
> h6310

understood, thanks for clarifying. but in fact on my system (OSX, groff 1.22.4 installed via 
macports) I get

x T ps
x res 72000 1 1
x init
p1
x font 10 SS
f10
s10000
V12000
H72000
md
DFd
C*a
h5620
n12000 0
x trailer
V792000
x stop

so here grops actually uses SS by default (in line with what the DESC file 
says).

but anyway... my real problem is that grops using SS messes up eqn output quite severely while the 
respective greek letters do not look slanted at all (in case the ML accepts
mail attachments: see attachments :)). if use of S is enforced, the grops 
output looks correct
using unslanted glyphs (2nd attachment).

although I can now work around the issue by simply enforcing that grops uses S (even on my 
system...), I wonder what is going on here, altogether? why does the use of SS a) lead to 
misalingment/mispositioning of eqn output, b) yield (seemingly) the actual insertion of unslanted 
("S") glyphs but with wrong width etc.?

regarding gropdf usage together with eqn I will just say that it does not play that well together. 
things like minus sign following, e.g. a "rho" touching the preceding letter, i.e. no gap or 
superscripts (e.g power of 2) also touching preceding slanted greek letter. this principally 
excludes serious use of gropdf in conjunction with eqn I would say. so that would be an independent 
issue: are there measures needed and possible to implement to adjust the spacing so that the
slanted greek letters also work in equations?

best,
joerg

Screenshot 2022-07-26 at 19.15.01.png
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Screenshot 2022-07-26 at 19.05.23.png
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