Re: [groff] gropdf(1) Has Ugly Thick Lines by Default.

[Deri]

On Saturday, 28 July 2018 14:37:14 BST Ralph Corderoy wrote:
> I think grops should copy grops's choice of default line width.
> And the differences in coordinates seem odd.  Even if they're correctly
> compensating for line-cap differences, should those differences exist?

Hi Ralph,

I agree. grops.cpp has a DEFAULT_LINEWIDTH set to 40 (ems/1000). So I will 
include 0.4 w when I set up the graphics environment at the start of each new 
page.

I have recently (during the recent discussion on changing linecaps within pic) 
realised I should be using "S" for stroking rather than "s", so the path is 
closed. This prevented the linecaps being changed when using the example given 
and gropdf.

As regards the difference in coordinates, I am a bit baffled. The groff 
intermediate output for the first line is:-

x T pdf
x res 72000 1 1
x init
x F -
p1
x F -
V2000
H72000
DFd
v2500
md
s10000
Dl 13330 0
n2000 0

So it looks like the horizontal position of the start of the line is 72000 
millipoints in and 4500 millipoints down from the top of the page and is 13330 
millipoints long. This is what the postscript file contains:-

4 LW 85.33 4.5 72 4.5 DL

Which seems correct. One difference between postscript and pdf is that ps has 
page origin at the top left whereas pdf uses the bottom left. Since the page 
is A4 the top of the page is 842 points so gropdf using 837.5 is expected. It 
appears that the difference in coordinates is being introduced by conversion 
from postscript to pdf!

It does not seem to be associated with the linecaps, nor the length of the 
line, since using a very wide (10pt) linewidth and longer line does not alter 
the amount it is shifted. I wondered whether ghostscript is looking at my 
default printer and adjusting for printable area, but I have not tested this.

Finally, the unnecessary switching between text and graphic mode you have 
noted, I believe this is because I have wrongly assumed that the presence of 
an absolute positioning command was a precursor to receiving text, so it 
switches mode, I shall think some more on this. :-(

Cheers 

Deri