Unit arithmetic objects are lists.

Fixes #1437

Author: hadley

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 2.0.0.9000
 
+* You can once again set legend key and height width to unit arithmetic
+  objects (like `2 * unit(1, "cm")`) (#1437).
+
 * When mapping an aesthetic to a constant (e.g. 
   `geom_smooth(aes(colour = "loess")))`), the default guide title is the name 
   of the aesthetic, not the value (#1431).

R/utilities-grid.r

@@ -16,21 +16,21 @@ ggname <- function(prefix, grob) {
 width_cm <- function(x) {
   if (is.grob(x)) {
     convertWidth(grobWidth(x), "cm", TRUE)
-  } else if (is.list(x)) {
-    vapply(x, width_cm, numeric(1))
   } else if (is.unit(x)) {
     convertWidth(x, "cm", TRUE)
+  } else if (is.list(x)) {
+    vapply(x, width_cm, numeric(1))
   } else {
     stop("Unknown input")
   }
 }
 height_cm <- function(x) {
   if (is.grob(x)) {
     convertWidth(grobHeight(x), "cm", TRUE)
-  } else if (is.list(x)) {
-    vapply(x, height_cm, numeric(1))
   } else if (is.unit(x)) {
     convertHeight(x, "cm", TRUE)
+  } else if (is.list(x)) {
+    vapply(x, height_cm, numeric(1))
   } else {
     stop("Unknown input")
   }

tests/testthat/test-grid-utils.R

@@ -0,0 +1,8 @@
+context("Grid utilites")
+
+test_that("width_cm and height_cm work with unit arithmetic", {
+  x <- 2 * unit(1, "cm")
+
+  expect_equal(width_cm(x), 2)
+  expect_equal(height_cm(x), 2)
+})