replace fallback mechanism

Author: teunbrand

R/scale-.R

@@ -598,7 +598,7 @@ Scale <- ggproto("Scale", NULL,
     if (empty(df)) {
       return()
     }
-    self$palette <- self$palette %||% fallback_palette(self)
+    self$palette <- self$palette %||% fetch_ggproto(self, "fallback_palette")
 
     aesthetics <- intersect(self$aesthetics, names(df))
     names(aesthetics) <- aesthetics

R/scales-.R

@@ -183,7 +183,7 @@ ScalesList <- ggproto("ScalesList", NULL,
       elem <- compact(lapply(elem, calc_element, theme))[1][[1]]
 
       # Resolve the palette itself
-      elem <- elem %||% fallback_palette(scale)
+      elem <- elem %||% fetch_ggproto(scale, "fallback_palette")
       palette <- switch(
         type,
         discrete   = as_discrete_pal(elem),

R/utilities.R

@@ -810,34 +810,6 @@ size0 <- function(x) {
   }
 }
 
-fallback_palette <- function(scale) {
-  aes <- scale$aesthetics[1]
-  discrete <- scale$is_discrete()
-  if (discrete) {
-    pal <- switch(
-      aes,
-      colour = , fill = pal_hue(),
-      alpha = function(n) seq(0.1, 1, length.out = n),
-      linewidth = function(n) seq(2, 6, length.out = n),
-      linetype = pal_linetype(),
-      shape = pal_shape(),
-      size = function(n) sqrt(seq(4, 36, length.out = n)),
-      ggplot_global$theme_default[[paste0("palette.", aes, ".discrete")]]
-    )
-    return(pal)
-  }
-  switch(
-    aes,
-    colour = , fill = pal_seq_gradient("#132B43", "#56B1F7"),
-    alpha = pal_rescale(c(0.1, 1)),
-    linewidth = pal_rescale(c(1, 6)),
-    linetype = pal_binned(pal_linetype()),
-    shape = pal_binned(pal_shape()),
-    size = pal_area(),
-    ggplot_global$theme_default[[paste0("palette.", aes, ".continuous")]]
-  )
-}
-
 warn_dots_used <- function(env = caller_env(), call = caller_env()) {
   check_dots_used(
     env = env, call = call,