adds visibility helpers

Author: gaboesquivel

helpers/_visibility.scss

@@ -0,0 +1,50 @@
+/*
+ * Hide visually and from screen readers:
+ * http://juicystudio.com/article/screen-readers-display-none.php
+ */
+
+.hidden {
+    display: none !important;
+    visibility: hidden;
+}
+
+/*
+ * Hide only visually, but have it available for screen readers:
+ * http://snook.ca/archives/html_and_css/hiding-content-for-accessibility
+ */
+
+.visuallyhidden {
+    border: 0;
+    clip: rect(0 0 0 0);
+    height: 1px;
+    margin: -1px;
+    overflow: hidden;
+    padding: 0;
+    position: absolute;
+    width: 1px;
+}
+
+/*
+ * Extends the .visuallyhidden class to allow the element
+ * to be focusable when navigated to via the keyboard:
+ * https://www.drupal.org/node/897638
+ */
+
+.visuallyhidden.focusable:active,
+.visuallyhidden.focusable:focus {
+    clip: auto;
+    height: auto;
+    margin: 0;
+    overflow: visible;
+    position: static;
+    width: auto;
+}
+
+/*
+ * Hide visually and from screen readers, but maintain layout
+ */
+
+.invisible {
+    visibility: hidden;
+}
+