adjusting geom_* default colour based upon theme element

a first hack: adding a new theme element `geom.colour` and passing theme to ggplot_build so that it can be called in `use_defaults` to override the `colour` default only when applicable and not set by `params` or mapped to data.

R/geom-.r

@@ -107,21 +107,27 @@ Geom <- ggproto("Geom",
   setup_data = function(data, params) data,
 
   # Combine data with defaults and set aesthetics from parameters
-  use_defaults = function(self, data, params = list()) {
+  use_defaults = function(self, data, params = list(), th) {
+
     # Fill in missing aesthetics with their defaults
     missing_aes <- setdiff(names(self$default_aes), names(data))
 
     missing_eval <- lapply(self$default_aes[missing_aes], rlang::eval_tidy)
     # Needed for geoms with defaults set to NULL (e.g. GeomSf)
     missing_eval <- compact(missing_eval)
 
+    # transform defaults based on theme
+    if ("colour" %in% names(missing_eval) && !is.na(missing_eval$colour)) {
+      missing_eval$colour <- th$geom.colour
+    }
+
     if (empty(data)) {
       data <- as_gg_data_frame(missing_eval)
     } else {
       data[names(missing_eval)] <- missing_eval
     }
 
-    # Override mappings with params
+    # Override mappings [and theme] with params
     aes_params <- intersect(self$aesthetics(), names(params))
     check_aesthetics(params[aes_params], nrow(data))
     data[aes_params] <- params[aes_params]

R/layer.r

@@ -303,11 +303,11 @@ Layer <- ggproto("Layer", NULL,
     self$position$compute_layer(data, params, layout)
   },
 
-  compute_geom_2 = function(self, data) {
+  compute_geom_2 = function(self, data, th) {
     # Combine aesthetics, defaults, & params
     if (empty(data)) return(data)
 
-    self$geom$use_defaults(data, self$aes_params)
+    self$geom$use_defaults(data, self$aes_params, th)
   },
 
   finish_statistics = function(self, data) {

R/plot-build.r

@@ -87,7 +87,8 @@ ggplot_build.ggplot <- function(plot) {
   }
 
   # Fill in defaults etc.
-  data <- by_layer(function(l, d) l$compute_geom_2(d))
+  theme <- plot_theme(plot)
+  data <- by_layer(function(l, d) l$compute_geom_2(d, th = theme))
 
   # Let layer stat have a final say before rendering
   data <- by_layer(function(l, d) l$finish_statistics(d))
@@ -137,7 +138,7 @@ layer_grob <- function(plot, i = 1L) {
 #' to (e.g.) make the legend box 2 cm wide, or combine multiple plots into
 #' a single display, preserving aspect ratios across the plots.
 #'
-#' @seealso [print.ggplot()] and \code{link{benchplot}} for
+#' @seealso [print.ggplot()] and \code{\link{benchplot}} for
 #'  for functions that contain the complete set of steps for generating
 #'  a ggplot2 plot.
 #' @return a [gtable()] object

R/theme-defaults.r

@@ -100,6 +100,7 @@ theme_grey <- function(base_size = 11, base_family = "",
                             margin = margin(), debug = FALSE
                          ),
 
+    geom.colour =        "black",
     axis.line =          element_blank(),
     axis.line.x =        NULL,
     axis.line.y =        NULL,
@@ -342,6 +343,9 @@ theme_dark <- function(base_size = 11, base_family = "",
       # match legend key to panel.background
       legend.key       = element_rect(fill = "grey50", colour = NA),
 
+      # make geom stand out in white
+      geom.colour      = "white",
+
       # dark strips with light text (inverse contrast compared to theme_grey)
       strip.background = element_rect(fill = "grey15", colour = NA),
       strip.text       = element_text(

R/theme-elements.r

@@ -262,6 +262,7 @@ el_def <- function(class = NULL, inherit = NULL, description = NULL) {
   rect                = el_def("element_rect"),
   text                = el_def("element_text"),
   title               = el_def("element_text", "text"),
+  geom.colour         = el_def("character"),
   axis.line           = el_def("element_line", "line"),
   axis.text           = el_def("element_text", "text"),
   axis.title          = el_def("element_text", "title"),

R/theme.r

@@ -20,7 +20,7 @@
 #' @param title all title elements: plot, axes, legends (`element_text`;
 #'   inherits from `text`)
 #' @param aspect.ratio aspect ratio of the panel
-#'
+#' @param geom.colour override default geom_* colour
 #' @param axis.title label of axes (`element_text`; inherits from
 #'   `text`)
 #' @param axis.title.x x axis label (`element_text`; inherits from
@@ -290,6 +290,7 @@ theme <- function(line,
                   text,
                   title,
                   aspect.ratio,
+                  geom.colour,
                   axis.title,
                   axis.title.x,
                   axis.title.x.top,