X-Git-Url: http://source.bookstackapp.com/bookstack/blobdiff_plain/d1a4ff930872fd77dc18fae02870ec057098b36b..refs/pull/695/head:/resources/assets/js/pages/page-show.js

diff --git a/resources/assets/js/pages/page-show.js b/resources/assets/js/pages/page-show.js
index 14437cd68..2efaf66c6 100644
--- a/resources/assets/js/pages/page-show.js
+++ b/resources/assets/js/pages/page-show.js
@@ -1,5 +1,5 @@
 const Clipboard = require("clipboard");
-const Code = require('../code');
+const Code = require('../libs/code');
 
 let setupPageShow = window.setupPageShow = function (pageId) {
 
@@ -102,23 +102,28 @@ let setupPageShow = window.setupPageShow = function (pageId) {
     let $window = $(window);
     let $sidebar = $("#sidebar .scroll-body");
     let $bookTreeParent = $sidebar.parent();
+
     // Check the page is scrollable and the content is taller than the tree
     let pageScrollable = ($(document).height() > $window.height()) && ($sidebar.height() < $('.page-content').height());
+
     // Get current tree's width and header height
     let headerHeight = $("#header").height() + $(".toolbar").height();
     let isFixed = $window.scrollTop() > headerHeight;
-    // Function to fix the tree as a sidebar
+
+    // Fix the tree as a sidebar
     function stickTree() {
         $sidebar.width($bookTreeParent.width() + 15);
         $sidebar.addClass("fixed");
         isFixed = true;
     }
-    // Function to un-fix the tree back into position
+
+    // Un-fix the tree back into position
     function unstickTree() {
         $sidebar.css('width', 'auto');
         $sidebar.removeClass("fixed");
         isFixed = false;
     }
+
     // Checks if the tree stickiness state should change
     function checkTreeStickiness(skipCheck) {
         let shouldBeFixed = $window.scrollTop() > headerHeight;
@@ -150,6 +155,59 @@ let setupPageShow = window.setupPageShow = function (pageId) {
             unstickTree();
         }
     });
+
+
+    // Check if support is present for IntersectionObserver
+    if ('IntersectionObserver' in window &&
+        'IntersectionObserverEntry' in window &&
+        'intersectionRatio' in window.IntersectionObserverEntry.prototype) {
+        addPageHighlighting();
+    }
+
+    function addPageHighlighting() {
+      let pageNav = document.querySelector('.sidebar-page-nav');
+
+      // fetch all the headings.
+      let headings = document.querySelector('.page-content').querySelectorAll('h1, h2, h3, h4, h5, h6');
+      // if headings are present, add observers.
+      if (headings.length > 0 && pageNav !== null) {
+          addNavObserver(headings);
+      }
+
+      function addNavObserver(headings) {
+          // Setup the intersection observer.
+          let intersectOpts = {
+              rootMargin: '0px 0px 0px 0px',
+              threshold: 1.0
+          };
+          let pageNavObserver = new IntersectionObserver(headingVisibilityChange, intersectOpts);
+
+          // observe each heading
+          for (let i = 0; i !== headings.length; ++i) {
+              pageNavObserver.observe(headings[i]);
+          }
+      }
+
+      function headingVisibilityChange(entries, observer) {
+          for (let i = 0; i < entries.length; i++) {
+              let currentEntry = entries[i];
+              let isVisible = (currentEntry.intersectionRatio === 1);
+              toggleAnchorHighlighting(currentEntry.target.id, isVisible);
+          }
+      }
+
+        function toggleAnchorHighlighting(elementId, shouldHighlight) {
+            let anchorsToHighlight = pageNav.querySelectorAll('a[href="#' + elementId + '"]');
+            for (let i = 0; i < anchorsToHighlight.length; i++) {
+                // Change below to use classList.toggle when IE support is dropped.
+                if (shouldHighlight) {
+                    anchorsToHighlight[i].classList.add('current-heading');
+                } else {
+                    anchorsToHighlight[i].classList.remove('current-heading');
+                }
+            }
+        }
+    }
 };
 
 module.exports = setupPageShow;
\ No newline at end of file