feat: resolve #7 theme_civilytics(): default to a transparent background, opt-in for Civilytics cream

R/theme.R

@@ -36,10 +36,14 @@
 #'   to [civilytics_colors]`["paper_2"]` (`#F2EDE4`).
 #' @param grid Character. Which major gridlines to draw: `"y"` (default,
 #'   horizontal only), `"x"` (vertical only), `"both"`, or `"none"`.
-#' @param paper_bg Logical. If `TRUE` (default), fill the plot and panel
-#'   backgrounds with the warm `paper` color. Set to `FALSE` for a
-#'   transparent background (useful for slides or overlay on colored
-#'   surfaces).
+#' @param paper_bg Logical. If `TRUE`, fill the plot and panel
+#'   backgrounds with the warm `paper` color (the Civilytics cream,
+#'   `#FAF7F2`). Default is `FALSE` for a transparent background,
+#'   which composes cleanly onto report pages, slides, and web
+#'   backgrounds of any color. To get fully transparent PNGs you also
+#'   need a transparent graphics device (e.g. `ragg::agg_png(...,
+#'   background = "transparent")`); the theme alone cannot make the
+#'   device canvas transparent.
 #'
 #' @section Font size hierarchy:
 #' All text sizes are derived from `font_size` using relative scale factors.
@@ -68,7 +72,7 @@
 #' \dontrun{
 #' library(ggplot2)
 #'
-#' # Default editorial theme
+#' # Default editorial theme (transparent background)
 #' ggplot(mpg, aes(displ, hwy)) +
 #'   geom_point() +
 #'   theme_civilytics()
@@ -79,10 +83,10 @@
 #'   scale_color_civilytics() +
 #'   theme_civilytics(grid = "both")
 #'
-#' # Transparent background for embedding
+#' # Branded cream paper canvas (opt-in)
 #' ggplot(mpg, aes(displ, hwy)) +
 #'   geom_point() +
-#'   theme_civilytics(paper_bg = FALSE)
+#'   theme_civilytics(paper_bg = TRUE)
 #'
 #' # Larger text for poster or display
 #' ggplot(mpg, aes(displ, hwy)) +
@@ -102,7 +106,7 @@ theme_civilytics <- function(
     accent       = unname(civilytics_colors["ember_600"]),
     strip_color  = unname(civilytics_colors["paper_2"]),
     grid         = c("y", "x", "both", "none"),
-    paper_bg     = TRUE) {
+    paper_bg     = FALSE) {
 
   grid <- match.arg(grid)
   half_line  <- font_size / 2

tests/testthat/test_theme.R

@@ -133,9 +133,10 @@ test_that("theme_civilytics uses brand ink color for text", {
   expect_equal(th$text$colour, unname(civilytics_colors["ink"]))
 })
 
-test_that("theme_civilytics uses brand paper color for plot background", {
+test_that("theme_civilytics defaults to transparent plot background", {
   th <- theme_civilytics()
-  expect_equal(th$plot.background$fill, unname(civilytics_colors["paper"]))
+  expect_true(is.na(th$plot.background$fill))
+  expect_true(is.na(th$panel.background$fill))
 })
 
 test_that("theme_civilytics uses paper_2 for strip background by default", {
@@ -178,10 +179,10 @@ test_that("theme_civilytics grid parameter controls gridlines", {
   expect_s3_class(th_none$panel.grid.major.y, "element_blank")
 })
 
-test_that("theme_civilytics paper_bg=FALSE gives transparent background", {
-  th <- theme_civilytics(paper_bg = FALSE)
-  expect_true(is.na(th$plot.background$fill))
-  expect_true(is.na(th$panel.background$fill))
+test_that("theme_civilytics paper_bg=TRUE gives cream paper background", {
+  th <- theme_civilytics(paper_bg = TRUE)
+  expect_equal(th$plot.background$fill, unname(civilytics_colors["paper"]))
+  expect_equal(th$panel.background$fill, unname(civilytics_colors["paper"]))
 })
 
 test_that("theme_civilytics has plot-aligned title and caption", {