1 files changed, 49 insertions, 0 deletions
diff --git a/themes/docsy/assets/js/anchor.js b/themes/docsy/assets/js/anchor.js
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index 000000000..9d8a0e678
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+++ b/themes/docsy/assets/js/anchor.js
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2018 Google LLC
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    https://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+(function ($) {
+    'use strict';
+
+    // Headers' anchor link that shows on hover
+    $(function () {
+        // append anchor links to headings in markdown.
+        var article = document.getElementsByTagName('main')[0];
+        if (!article) {
+            return;
+        }
+        var headings = article.querySelectorAll('h1, h2, h3, h4, h5, h6');
+        headings.forEach(function (heading) {
+            if (heading.id) {
+                var a = document.createElement('a');
+                // set visibility: hidden, not display: none to avoid layout change
+                a.style.visibility = 'hidden';
+                // [a11y] hide this from screen readers, etc..
+                a.setAttribute('aria-hidden', 'true');
+                // material insert_link icon in svg format
+                a.innerHTML = ' <svg xmlns="http://www.w3.org/2000/svg" fill="currentColor" width="24" height="24" viewBox="0 0 24 24"><path d="M0 0h24v24H0z" fill="none"/><path d="M3.9 12c0-1.71 1.39-3.1 3.1-3.1h4V7H7c-2.76 0-5 2.24-5 5s2.24 5 5 5h4v-1.9H7c-1.71 0-3.1-1.39-3.1-3.1zM8 13h8v-2H8v2zm9-6h-4v1.9h4c1.71 0 3.1 1.39 3.1 3.1s-1.39 3.1-3.1 3.1h-4V17h4c2.76 0 5-2.24 5-5s-2.24-5-5-5z"/></svg>';
+                a.href = '#' + heading.id;
+                heading.insertAdjacentElement('beforeend', a);
+                heading.addEventListener('mouseenter', function () {
+                    a.style.visibility = 'initial';
+                });
+                heading.addEventListener('mouseleave', function () {
+                    a.style.visibility = 'hidden';
+                });
+            }
+        });
+    });
+
+}(jQuery));