Simplify zeroGrob()

DESCRIPTION

@@ -173,7 +173,6 @@ Collate:
     'ggplot2-package.R'
     'grob-absolute.R'
     'grob-dotstack.R'
-    'grob-null.R'
     'grouping.R'
     'theme-elements.R'
     'guide-.R'

NAMESPACE

@@ -19,7 +19,6 @@ S3method(as.list,ggproto)
 S3method(autolayer,default)
 S3method(autoplot,default)
 S3method(c,mapped_discrete)
-S3method(drawDetails,zeroGrob)
 S3method(element_grob,element_blank)
 S3method(element_grob,element_line)
 S3method(element_grob,element_point)
@@ -76,9 +75,7 @@ S3method(ggplot_gtable,ggplot_built)
 S3method(grid.draw,absoluteGrob)
 S3method(grid.draw,ggplot)
 S3method(grobHeight,absoluteGrob)
-S3method(grobHeight,zeroGrob)
 S3method(grobWidth,absoluteGrob)
-S3method(grobWidth,zeroGrob)
 S3method(grobX,absoluteGrob)
 S3method(grobY,absoluteGrob)
 S3method(guide_gengrob,default)
@@ -87,7 +84,6 @@ S3method(guide_merge,default)
 S3method(guide_train,default)
 S3method(guide_transform,default)
 S3method(heightDetails,titleGrob)
-S3method(heightDetails,zeroGrob)
 S3method(limits,Date)
 S3method(limits,POSIXct)
 S3method(limits,POSIXlt)
@@ -149,7 +145,6 @@ S3method(vec_ptype2,mapped_discrete.factor)
 S3method(vec_ptype2,mapped_discrete.integer)
 S3method(vec_ptype2,mapped_discrete.mapped_discrete)
 S3method(widthDetails,titleGrob)
-S3method(widthDetails,zeroGrob)
 export("%+%")
 export("%+replace%")
 export(.data)

NEWS.md

@@ -1,5 +1,6 @@
 # ggplot2 (development version)
 
+* (internal) `zeroGrob()` now returns a `grid::nullGrob()` (#6390).
 * `position_fill()` avoids stacking observations of zero (@teunbrand, #6338)
 * New `layer(layout)` argument to interact with facets (@teunbrand, #3062)
 * New `stat_connect()` to connect points via steps or other shapes 

R/utilities-grid.R

@@ -48,6 +48,17 @@ gg_par <- function(..., stroke = NULL, pointsize = NULL) {
   inject(gpar(!!!args))
 }
 
+#' The zero grob draws nothing and has zero size.
+#'
+#' @keywords internal
+#' @export
+zeroGrob <- function() .zeroGrob
+
+.zeroGrob <- NULL
+on_load(.zeroGrob <- add_class(nullGrob(), "zeroGrob"))
+
+is.zero <- function(x) is.null(x) || inherits(x, "null")
+
 width_cm <- function(x) {
   if (is.grob(x)) {
     convertWidth(grobWidth(x), "cm", TRUE)

R/utilities.R

@@ -959,3 +959,12 @@
   data[[target]] <- res * (default %||% 0.9)
   data
 }
+
+add_class <- function(x, new_class) {
+  new_class <- setdiff(new_class, class(x))
+  if (length(new_class) < 1) {
+    return(x)
+  }
+  class(x) <- union(new_class, class(x))
+  x
+}

tests/testthat/test-facet-strips.R

@@ -132,7 +132,7 @@ test_that("strips can be removed", {
     theme(strip.background = element_blank(), strip.text = element_blank())
   g_grobs <- ggplotGrob(g)
   strip_grobs <- g_grobs$grobs[grepl('strip-', g_grobs$layout$name)]
-  expect_true(all(sapply(strip_grobs, inherits, 'zeroGrob')))
+  expect_true(all(sapply(strip_grobs, inherits, 'null')))
 })
 
 test_that("padding is only added if axis is present", {

tests/testthat/test-stat-density2d.R

@@ -100,5 +100,5 @@ test_that("stat_density_2d handles faulty bandwidth", {
   p <- ggplot(faithful, aes(eruptions, waiting)) +
     stat_density_2d(h = c(0, NA))
   expect_snapshot_warning(b <- ggplot_build(p))
-  expect_s3_class(layer_grob(b)[[1]], "zeroGrob")
+  expect_s3_class(layer_grob(b)[[1]], "null")
 })