Dispatch ellipsis (...) to more than one function

Question

... is fine to dispatch additional arguments to functions within a function. I use it, among others, to maintain parsimonious function declarations with not a ton of arguments. But sometimes, I would need that more than a single function could make use of additional arguments passed to the function.

Maybe an example would make this clear:

heart <- structure(c(200, 162, 116, 99, 118, 164, 202, 242, 288, 305, 
                     284, 238, 37, 76, 108, 154, 200, 211, 175, 211, 197, 151, 105, 
                     73), .Dim = c(12L, 2L), .Dimnames = list(NULL, c("x", "y")))

# both functions in this function would benefit using `...`
plot_this <- function(xy, ...){
  plot(xy, ...)
  polygon(xy, ...)
}

Then, calling this function with arguments that only "concern" one function (ie asp for plot and density for polygon) will (most of the time) work but with warnings.

plot_this(heart, asp=1, density=30)

Warning messages:
1: In plot.window(...) : "density" is not a graphical parameter
2: In plot.xy(xy, type, ...) : "density" is not a graphical parameter
3: In axis(side = side, at = at, labels = labels, ...) :
  "density" is not a graphical parameter
4: In axis(side = side, at = at, labels = labels, ...) :
  "density" is not a graphical parameter
5: In box(...) : "density" is not a graphical parameter
6: In title(...) : "density" is not a graphical parameter

I understand that these warnings are perfectly legitimate and useful.

Is there a mechanism to deal with dispatching ellipsis to the 'right' functions when more use ... within a function?".

I'm looking for something:

• more elegant than using this pattern ..._polygon or args.polygon
• possibly simpler than around formals as answered there
• less rough than suppressWarnings()