{png,pdf}cairo terminals and font size

[Allin C. <cot...@wf...>]

I like the *cairo terminals a lot: PNG looks good on screen and
PDF is good for publication-quality output; and these two
terminals share a common command-set with high fidelity, since
they use a common back-end.  Except for one thing...

The help for both pngcairo and pdfcairo says that the default size
for fonts is 6 points.  That's fine, and if you go with the
default you get quite consistent-looking output from the two
terminals.

But if you alter the size, an inconsistency emerges.  Suppose I'd
prefer 8 points.  I do my PNG plot using

set term pngcairo font ",8"

then do my PDF plot using

set term pdfcairo font ",8"

Relative to the "6-point" baseline, the PNG file shows a smaller
font (8 < 6, hmm) while the PDF plot shows a larger font (8 > 6).

I'm happy to take a look at the code and see if I can come up with
a patch for this.  But I'd rather hear any comments first.

Allin Cottrell