feat(visible): small utility function for visibility

DESCRIPTION

@@ -54,5 +54,6 @@ Collate:
     'shadow.R'
     'text.R'
     'utils-docs.R'
+    'visible.R'
     'width.R'
     'zzz.R'

NAMESPACE

@@ -22,6 +22,7 @@ export(padding)
 export(position)
 export(shadow)
 export(text)
+export(visible)
 export(width)
 export(with_style)
 import(rlang)

R/visible.R

@@ -0,0 +1,34 @@
+visible_value <- function(value) {
+  if (is_true(value)) {
+    "visible"
+  } else if (is_false(value)) {
+    "invisible"
+  }
+}
+
+#' Element visibility
+#'
+#' The `visible()` function changes the visibility of a tag element. An
+#' invisible element is both visually hidden and is also hidden from screen
+#' readers.
+#'
+#' @inheritParams background
+#'
+#' @param value One of `TRUE` or `FALSE` specifying if the element is visible,
+#'   defaults to `TRUE`.
+#'
+#' @export
+#' @examples
+#'
+#' library(htmltools)
+#'
+#' div("I am hidden") %>%
+#'   visible(FALSE)
+#'
+visible <- function(x, value) {
+  assert_subject(x)
+
+  class <- visible_value(value)
+
+  add_class(x, class)
+}

tests/testthat/test-visible.R

@@ -0,0 +1,11 @@
+context("visible()")
+
+test_that("adds classes", {
+  div() %>%
+    visible(FALSE) %>%
+    expect_html_class("invisible")
+
+  div() %>%
+    visible(TRUE) %>%
+    expect_html_class("visible")
+})