Could calc_element theme argument default to ggplot2::get_theme?

[davidhodge931]

Lots of people work with ggplot2 primarily by setting a global theme.

For this reason, I was wondering if you'd consider changing the default theme argument in calc_element to ggplot2::get_theme.

calc_element(
  element,
  theme = ggplot2::get_theme(),
  verbose = FALSE,
  skip_blank = FALSE,
  call = caller_env()
)

[teunbrand]

I like this idea, but it should use complete_theme() instead of get_theme() to reliably reproduce what ggplot2 itself does internally. The complete_theme() already uses get_theme() as default. This will make it more 'expensive' than simply using get_theme() as default.