setting style xthickness/ythickness

[Kevin Ryde <user42 zip com au>]

Is there a right way to set field values in a Gtk2::Style, like
xthickness.  $style->xthickness() is only an accessor, if I'm not
mistaken.

Dunno what the right thing to do in C code is.  Just plonk a value in
the struct?  (A copy of the struct if it belongs to someone else of
course.)  Could the same be done from perl?

I thought to change some style settings from program code and stick the
changed style onto selected widgets.  It's not for anything important,
and I get close enough with a Gtk2::Rc->parse_string() with new values,
but wondered if it was possible to operate programmatically on style
objects as such.