This PR is a proof-of-concept for support ofunit() throughout ggplot2. It shows how some of the ideas in#5609 might be implemented.

To tease, it would allow you to do stuff like this:

data.frame(var1=1:5,var2=1:5,name=letters[1:5])|>  ggplot(aes(var1,var2))+   geom_point()+  geom_line()+# labels exactly 10 points right of their points, no matter how the# plot is resized  geom_text(aes(label=name,x=var1+ as_pt(10)))+# an annotation that is always 10 points inset from the lower right  annotate("text",x= as_npc(1)- as_pt(10),y= as_pt(10),label="some label",vjust=0,hjust=1  )+  coord_polar()

It is a draft only for several reasons:

1. Several of the proposed changes probably shouldn't live in ggplot2, but in vctrs, grid, or perhaps scales.
2. This is just a prototype, not a comprehensive, solid, well-tested solution.
3. While the solution for positional aesthetics (I think) covers most cases, the solution for non-positional aesthetics is only mocked up forgeom_point().

Would love to hear folks' thoughts, or if I am barking up the wrong tree...