Re: [Gnuplot-info] unicode points are shifted

[Norwid B. <nb...@ya...>]

@Dmitry Preface: I'm not yet convinced a character pointtype by `"\U+25A2"`
improves the default tools available if one wants to indicate the points'
location by a box.  The difference is gnuplot's box does not use rounded
corners -- is this a requirement on your side?  Because depending on font and
specific glyph, what is the origin of coordinates of its bounding box (in
LaTeX's parlance) gnuplot uses a reference to put the glyph on the canvas --
is it in one of the bounding box' corners, or its center (then affected by the
glyph's height and width)?[1]  Would using the "rounded square" render the plot
much easier to read, than gnuplot's box?  Perhaps the script shared by you used
`"\U+25A2"` as a place holder for a different printable object.

My suggest is to use `pt 4` within the pdfcairo terminal to write an
intermediate .pdf subsequently converted e.g., by David Barton's pdf2svg[2]
in lines of `pdf2svg test.pdf out.svg`.  As an illustration, I edited your
script's header and last line to

``` test.spt
set terminal pdfcairo enhanced font 'DejaVuSans,12'
set output "test.pdf"

set style data lines
set title "error represented by xyerrorbars"
set xlabel "Resistance [Ohm]"
set ylabel "Power [W]"
n(x)=1.53**2*x/(5.67+x)**2
NO_ANIMATION = 1
unset pointintervalbox
#plot [0:50] "battery.dat" t "Power" with xyerrorbars pt "\U+25A1" pointsize
44 lw 2 lc "red", n(x) t "Theory" w lines #plot "battery.dat" t "Power" with
points pt "\U+25A1" pointsize 44 lw 2 lc "red"

plot [0:50] "battery.dat" with xyerrorbars pt -1 notitle ,\
"battery.dat" t "Power" with points pt 4 pointsize 1 lw 2 lc "red"
```

which works reasonably well (gnuplot 6.0.2).

[1] see for instance `x` and `V` in the accepted answer by `theozh` (May 26,
2019) https://stackoverflow.com/questions/56313642/change-the-color-of-a-character-pointtype-in-gnuplot
[2] http://cityinthesky.co.uk/opensource/pdf2svg/