Compute stat_sf() by panel instead of group (#5170)

* StatSf is computed per panel

* Add NEWS bullet

* Fix typo/reword

Author: teunbrand

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* To prevent changing the plotting order, `stat_sf()` is now computed per panel 
+  instead of per group (@teunbrand, #4340).
 * ggplot2 now uses `scales::DiscreteRange` and `scales::ContinuousRange`, which
   are available to write scale extensions from scratch (@teunbrand, #2710).
 * For the purposes of checking required or non-missing aesthetics, character 

R/stat-sf.R

@@ -9,7 +9,7 @@ StatSf <- ggproto("StatSf", Stat,
     ggproto_parent(Stat, self)$compute_layer(data, params, layout)
   },
 
-  compute_group = function(data, scales, coord) {
+  compute_panel = function(data, scales, coord) {
     geometry_data <- data[[ geom_column(data) ]]
     geometry_crs <- sf::st_crs(geometry_data)