add st_txt?

[SwampThingPaul]

Caveats:

1. I am relatively new to contributing to R-packages on github (apologize if this is the wrong way to do it).
2. I am still relatively new to sf (transitioning from sp and rgeos world).
3. I use sf to handle spatial data for analysis and produce (reproducible) maps

I was wondering if it would be worth adding a text function like raster::text(...)? Below is a function that I put together based on code from various packages. It also includes a "halo" option to highlight added text. If this is too much or the wrong time, not a problem.

st_txt=function(x, y=NULL, labels,halo=T, col='black', hc='white', hw=0.1, ...){
  if (missing(labels)) {
    labels <- 1
  }
  if (length(labels) != nrow(x)) {
    labels <- labels[1]
    if (is.character(labels)) {
      i <- which(labels == names(x))
      if (i == 0) {
        i <- 1
      }
    }
    labels <- x[[labels]]
    
  }
  xy <- sf::st_coordinates(sf::st_centroid(x))[,1:2, drop = FALSE]
  options(warn=-1)
  xy <- list(x = xy[,1, drop = TRUE], y = xy[,2, drop = TRUE])
  xo <- hw * graphics::strwidth('A')
  yo <- hw * graphics::strheight('A')
  
  if(halo==TRUE){
    theta <- seq(pi/4, 2*pi, length.out=8*hw*10)  
    for (i in theta){
      text( xy$x + cos(i)*xo, xy$y + sin(i)*yo, labels, col=hc, ... )
    }
    text(xy$x, xy$y, labels, col=col, ... )}else{
      text(xy$x, xy$y, labels, col=col, ... )
    }
  
}

Here is a working example.

library(sf)
library(USAboundaries)
utm17<-st_crs("EPSG:26917");# CRS for NAD83 UTM17

states.shp <- USAboundaries::us_states(resolution ="high")|>
  as("Spatial")|>
  st_as_sf()|>
  st_transform(utm17)|>
  subset(stusps%in%c("FL","GA","AL"))

plot(st_geometry(states.shp),col=c("grey","white","white"))
st_txt(states.shp,labels="stusps")
# A couple of variations based on different text arguments
st_txt(states.shp,labels="stusps",pos=4,offset=2,col="red",hc="yellow",font=2)
st_txt(states.shp,labels="stusps",pos=3,offset=2,col="blue")
st_txt(states.shp,labels="stusps",pos=2,offset=1.5,col="forestgreen")
st_txt(states.shp,labels="stusps",pos=1,offset=1,col="black",srt=45)

It should produce something like this:

[edzer]

To what extent can this be done with #2399?