From a132727e9de06dc43828b53de0257aa3fb76b33d Mon Sep 17 00:00:00 2001
From: Kara Woo <karawoo@users.noreply.github.com>
Date: Tue, 27 Oct 2020 20:39:55 -0700
Subject: [PATCH] Fix saving plots with no background (#4244)

* If plot theme background is null, set to transparent when saving

* Add test for svg with no background

* Make checking for NULL background more concise with %||%
---
 R/save.r                     |  2 +-
 tests/testthat/test-ggsave.R | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/R/save.r b/R/save.r
index 1bdd11381c..98bd10e99a 100644
--- a/R/save.r
+++ b/R/save.r
@@ -87,7 +87,7 @@ ggsave <- function(filename, plot = last_plot(),
     filename <- file.path(path, filename)
   }
   if (is_null(bg)) {
-    bg <- calc_element("plot.background", plot_theme(plot))$fill
+    bg <- calc_element("plot.background", plot_theme(plot))$fill %||% "transparent"
   }
   old_dev <- grDevices::dev.cur()
   dev(filename = filename, width = dim[1], height = dim[2], bg = bg, ...)
diff --git a/tests/testthat/test-ggsave.R b/tests/testthat/test-ggsave.R
index 491e8f5913..b4ee2cc4dc 100644
--- a/tests/testthat/test-ggsave.R
+++ b/tests/testthat/test-ggsave.R
@@ -44,6 +44,21 @@ test_that("ggsave uses theme background as image background", {
   expect_true(grepl("fill: #00CCCC", bg))
 })
 
+test_that("ggsave can handle blank background", {
+  skip_if_not_installed("xml2")
+
+  path <- tempfile()
+  on.exit(unlink(path))
+  p <- ggplot(mtcars, aes(disp, mpg)) +
+    geom_point() +
+    theme(plot.background = element_blank())
+  ggsave(path, p, device = "svg", width = 5, height = 5)
+  img <- xml2::read_xml(path)
+  bg <- as.character(xml2::xml_find_first(img, xpath = "d1:rect/@style"))
+  expect_true(grepl("fill: none", bg))
+})
+
+
 # plot_dim ---------------------------------------------------------------
 
 test_that("guesses and informs if dim not specified", {