getter for geom defaults

Author: teunbrand

DESCRIPTION

@@ -78,7 +78,7 @@ Config/testthat/edition: 3
 Encoding: UTF-8
 LazyData: true
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 7.3.1
+RoxygenNote: 7.3.2
 Collate: 
     'ggproto.R'
     'ggplot-global.R'

NAMESPACE

@@ -424,6 +424,7 @@ export(geom_violin)
 export(geom_vline)
 export(get_alt_text)
 export(get_element_tree)
+export(get_geom_defaults)
 export(get_guide_data)
 export(get_last_plot)
 export(get_layer_data)

R/geom-defaults.R

@@ -47,6 +47,58 @@ update_stat_defaults <- function(stat, new) {
   update_defaults(stat, "Stat", new, env = parent.frame())
 }
 
+#' Resolve and get geom defaults
+#'
+#' @param geom Some definition of a geom:
+#' * A `function` that creates a layer, e.g. `geom_path()`.
+#' * A layer created by such function
+#' * A string naming a geom class in snake case without the `geom_`-prefix,
+#'   e.g. `"contour_filled"`.
+#' * A geom class object.
+#' @param theme A [`theme`] object. Defaults to the current global theme.
+#'
+#' @return A list of aesthetics
+#' @export
+#' @keywords internal
+#'
+#' @examples
+#' # Using a function
+#' get_geom_defaults(geom_raster)
+#'
+#' # Using a layer includes static aesthetics as default
+#' get_geom_defaults(geom_tile(fill = "white"))
+#'
+#' # Using a class name
+#' get_geom_defaults("density_2d")
+#'
+#' # Using a class
+#' get_geom_defaults(GeomPoint)
+#'
+#' # Changed theme
+#' get_geom_defaults("point", theme(geom = element_geom(ink = "purple")))
+get_geom_defaults <- function(geom, theme = theme_get()) {
+  theme <- theme %||% list(geom = .default_geom_element)
+
+  if (is.function(geom)) {
+    geom <- geom()
+  }
+  if (is.layer(geom)) {
+    data <- data_frame0(.id = 1L)
+    data <- geom$compute_geom_2(data = data, theme = theme)
+    data$.id <- NULL
+    return(data)
+  }
+  if (is.character(geom)) {
+    geom <- check_subclass(geom, "Geom")
+  }
+  if (inherits(geom, "Geom")) {
+    out <- geom$use_defaults(data = NULL, theme = theme)
+    return(out)
+  }
+  stop_input_type(geom, as_cli("a layer function, string or {.cls Geom} object"))
+}
+
+
 cache_defaults <- new_environment()
 
 update_defaults <- function(name, subclass, new, env = parent.frame()) {