Linejoin settings for geom_step() (#5706)

* add linejoin params to `geom_step()`

* add news bullet

* tame long line

Author: teunbrand

NEWS.md

@@ -1,6 +1,8 @@
 
 # ggplot2 (development version)
 
+* `geom_step()` now supports `lineend`, `linejoin` and `linemitre` parameters 
+  (@teunbrand, #5705).
 * Fixed performance loss when the `.data` pronoun is used in `aes()` (#5730).
 * Fixed bug where discrete scales could not map aesthetics only consisting of
   `NA`s (#5623)

R/geom-path.R

@@ -322,9 +322,14 @@ geom_step <- function(mapping = NULL, data = NULL, stat = "identity",
 #' @export
 #' @include geom-path.R
 GeomStep <- ggproto("GeomStep", GeomPath,
-  draw_panel = function(data, panel_params, coord, direction = "hv") {
+  draw_panel = function(data, panel_params, coord,
+                        lineend = "butt", linejoin = "round", linemitre = 10,
+                        direction = "hv") {
     data <- dapply(data, "group", stairstep, direction = direction)
-    GeomPath$draw_panel(data, panel_params, coord)
+    GeomPath$draw_panel(
+      data, panel_params, coord,
+      lineend = lineend, linejoin = linejoin, linemitre = linemitre
+    )
   }
 )