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

R/theme.R

@@ -36,10 +36,9 @@
 #'   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 `FALSE` (default), the plot and panel
+#'   backgrounds are transparent (`fill = NA`). Set to `TRUE` to fill them
+#'   with the warm `paper` color for a branded cream canvas.
 #'
 #' @section Font size hierarchy:
 #' All text sizes are derived from `font_size` using relative scale factors.
@@ -64,11 +63,23 @@
 #' @return A complete ggplot2 [ggplot2::theme()] object.
 #' @export
 #'
+#' @section Transparent device background:
+#' Setting `paper_bg = FALSE` makes the theme's `plot.background` and
+#' `panel.background` transparent (`fill = NA`), but the graphics device
+#' itself may still paint a solid background. To produce fully transparent
+#' PNGs, also pass a transparent device background:
+#'
+#' ```r
+#' ragg::agg_png("plot.png", background = "transparent")
+#' print(p)
+#' dev.off()
+#' ```
+#'
 #' @examples
 #' \dontrun{
 #' library(ggplot2)
 #'
-#' # Default editorial theme
+#' # Default: transparent background
 #' ggplot(mpg, aes(displ, hwy)) +
 #'   geom_point() +
 #'   theme_civilytics()
@@ -79,10 +90,10 @@
 #'   scale_color_civilytics() +
 #'   theme_civilytics(grid = "both")
 #'
-#' # Transparent background for embedding
+#' # Branded cream 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 +113,7 @@ 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