[replying to groff@ from bug-groff@ so more people see this discussion] I wanted to make sure more people saw this because Deri's explanation is gold. I don't think there's any existing documentation that covers this anywhere nearly as lucidly.
Regards, Branden At 2022-07-26T17:19:04+0100, 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, > > 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. > > 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
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