From 5d0982e1f436e687a72ef7117078e608870a885c Mon Sep 17 00:00:00 2001
From: Thomas Lin Pedersen <thomasp85@gmail.com>
Date: Thu, 29 Aug 2019 14:50:12 +0200
Subject: [PATCH 1/2] Add setup_params method to Geom

---
 R/geom-.r | 2 ++
 R/layer.r | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/R/geom-.r b/R/geom-.r
index 21101bf052..bca1b57ded 100644
--- a/R/geom-.r
+++ b/R/geom-.r
@@ -104,6 +104,8 @@ Geom <- ggproto("Geom",
     stop("Not implemented")
   },
 
+  setup_params = function(data, params) params,
+
   setup_data = function(data, params) data,
 
   # Combine data with defaults and set aesthetics from parameters
diff --git a/R/layer.r b/R/layer.r
index cf0cfd15fd..e2f60a13e5 100644
--- a/R/layer.r
+++ b/R/layer.r
@@ -340,8 +340,8 @@ Layer <- ggproto("Layer", NULL,
       c(names(data), names(self$aes_params)),
       snake_class(self$geom)
     )
-
-    self$geom$setup_data(data, c(self$geom_params, self$aes_params))
+    self$geom_params <- self$geom$setup_params(data, c(self$geom_params, self$aes_params))
+    self$geom$setup_data(data, self$geom_params)
   },
 
   compute_position = function(self, data, layout) {

From df7662fa01a51ce1fbd8b7ffea2690d304716c6b Mon Sep 17 00:00:00 2001
From: Thomas Lin Pedersen <thomasp85@gmail.com>
Date: Thu, 29 Aug 2019 14:53:38 +0200
Subject: [PATCH 2/2] Add news bullet

---
 NEWS.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index 768c18064b..a25ea6d43f 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # ggplot2 (development version)
 
+* `Geom` now gains a `setup_params()` method in line with the other ggproto
+  classes (@thomasp85, #3509)
+
 * `element_text()` now issues a warning when vectorized arguments are provided, as in
   `colour = c("red", "green", "blue")`. Such use is discouraged and not officially supported
    (@clauswilke, #3492).