position-.r

# Position adjustment occurs over all groups within a geom
# They work only with discrete x scales and may affect x and y position.
# Should occur after statistics and scales have been applied.

Position <- proto(TopLevel, expr = {
  adjust <- function(., data, scales, ...) data

  class <- function(.) "position"
  
  width <- NULL
  height <- NULL
  new <- function(., width = NULL, height = NULL) {
    .$proto(width = width, height = NULL)
  }

  parameters <- function(.) {
    params <- formals(get("new", .))
    params[setdiff(names(params), c("."))]
  }
  
  pprint <- function(., newline=TRUE) {
    cat("position_", .$objname, ": ()", sep="")
    if (newline) cat("\n")
  }

  html_returns <- function(.) {
    ps(
      "<h2>Returns</h2>\n",
      "<p>This function returns a position object.</p>"
    )
  }
  
  parameters <- function(.) {
    params <- formals(get("new", .))
    params[setdiff(names(params), c(".","variable"))]
  }
  
})


# Convenience function to ensure that all position variables 
# (x, xmin, xmax, xend) are transformed in the same way
transform_position <- function(df, trans_x = NULL, trans_y = NULL) {
  scales <- aes_to_scale(names(df))

  if (!is.null(trans_x)) {
    df[scales == "x"] <- lapply(df[scales == "x"], trans_x)    
  }
  if (!is.null(trans_y)) {
    df[scales == "y"] <- lapply(df[scales == "y"], trans_y)
  }
  
  df
}