use affix plugin for reliable sticky detection

assets/_src/js/_faq.js

@@ -1,5 +1,6 @@
 
 //=include vendor/toc.js
+//=include vendor/affix.js
 
 var Faq = (function(w, d, $) {
 
@@ -27,29 +28,26 @@ var Faq = (function(w, d, $) {
             _config.faqToc.toc({
                 'selectors': _config.faqTitle, // elements to use as headings
                 'container': 'body', // element to find all selectors in
-                'highlightOffset': 200, // offset to trigger the next headline
+                'highlightOffset': 100, // offset to trigger the next headline
             });
         },
         faqTocSticky: function() {
             var win = $(window);
 
-            win.on('load resize scroll',function(e) {
+            win.on('load resize',function(e) {
                 if (_private.isWide()) {
-                    if ( win.scrollTop() > _config.faqTocColumn.offset().top) {
-                        _config.faqToc.addClass('sticky');
-                    } else {
-                        _config.faqToc.removeClass('sticky');
-                    }
-
-                    // TODO: remove sticky when bottom of content has been reached
+                    _config.faqToc.affix({
+                        offset: {
+                            top: ( _config.faqTocColumn.offset().top + 20 ),
+                            bottom: ( $('.section-faq:last-child').outerHeight(true) + 40 )
+                        }
+                    });
                 }
             });
         },
         isWide: function() {
             return $(window).width() >= _config.minWidth;
         }
-
-        // TODO: actually make section jumps work
     }
 
     app = {

assets/_src/js/vendor/affix.js

@@ -0,0 +1,162 @@
+/* ========================================================================
+ * Bootstrap: affix.js v3.3.6
+ * http://getbootstrap.com/javascript/#affix
+ * ========================================================================
+ * Copyright 2011-2016 Twitter, Inc.
+ * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
+ * ======================================================================== */
+
+
++function ($) {
+  'use strict';
+
+  // AFFIX CLASS DEFINITION
+  // ======================
+
+  var Affix = function (element, options) {
+    this.options = $.extend({}, Affix.DEFAULTS, options)
+
+    this.$target = $(this.options.target)
+      .on('scroll.bs.affix.data-api', $.proxy(this.checkPosition, this))
+      .on('click.bs.affix.data-api',  $.proxy(this.checkPositionWithEventLoop, this))
+
+    this.$element     = $(element)
+    this.affixed      = null
+    this.unpin        = null
+    this.pinnedOffset = null
+
+    this.checkPosition()
+  }
+
+  Affix.VERSION  = '3.3.6'
+
+  Affix.RESET    = 'affix affix-top affix-bottom'
+
+  Affix.DEFAULTS = {
+    offset: 0,
+    target: window
+  }
+
+  Affix.prototype.getState = function (scrollHeight, height, offsetTop, offsetBottom) {
+    var scrollTop    = this.$target.scrollTop()
+    var position     = this.$element.offset()
+    var targetHeight = this.$target.height()
+
+    if (offsetTop != null && this.affixed == 'top') return scrollTop < offsetTop ? 'top' : false
+
+    if (this.affixed == 'bottom') {
+      if (offsetTop != null) return (scrollTop + this.unpin <= position.top) ? false : 'bottom'
+      return (scrollTop + targetHeight <= scrollHeight - offsetBottom) ? false : 'bottom'
+    }
+
+    var initializing   = this.affixed == null
+    var colliderTop    = initializing ? scrollTop : position.top
+    var colliderHeight = initializing ? targetHeight : height
+
+    if (offsetTop != null && scrollTop <= offsetTop) return 'top'
+    if (offsetBottom != null && (colliderTop + colliderHeight >= scrollHeight - offsetBottom)) return 'bottom'
+
+    return false
+  }
+
+  Affix.prototype.getPinnedOffset = function () {
+    if (this.pinnedOffset) return this.pinnedOffset
+    this.$element.removeClass(Affix.RESET).addClass('affix')
+    var scrollTop = this.$target.scrollTop()
+    var position  = this.$element.offset()
+    return (this.pinnedOffset = position.top - scrollTop)
+  }
+
+  Affix.prototype.checkPositionWithEventLoop = function () {
+    setTimeout($.proxy(this.checkPosition, this), 1)
+  }
+
+  Affix.prototype.checkPosition = function () {
+    if (!this.$element.is(':visible')) return
+
+    var height       = this.$element.height()
+    var offset       = this.options.offset
+    var offsetTop    = offset.top
+    var offsetBottom = offset.bottom
+    var scrollHeight = Math.max($(document).height(), $(document.body).height())
+
+    if (typeof offset != 'object')         offsetBottom = offsetTop = offset
+    if (typeof offsetTop == 'function')    offsetTop    = offset.top(this.$element)
+    if (typeof offsetBottom == 'function') offsetBottom = offset.bottom(this.$element)
+
+    var affix = this.getState(scrollHeight, height, offsetTop, offsetBottom)
+
+    if (this.affixed != affix) {
+      if (this.unpin != null) this.$element.css('top', '')
+
+      var affixType = 'affix' + (affix ? '-' + affix : '')
+      var e         = $.Event(affixType + '.bs.affix')
+
+      this.$element.trigger(e)
+
+      if (e.isDefaultPrevented()) return
+
+      this.affixed = affix
+      this.unpin = affix == 'bottom' ? this.getPinnedOffset() : null
+
+      this.$element
+        .removeClass(Affix.RESET)
+        .addClass(affixType)
+        .trigger(affixType.replace('affix', 'affixed') + '.bs.affix')
+    }
+
+    if (affix == 'bottom') {
+      this.$element.offset({
+        top: scrollHeight - height - offsetBottom
+      })
+    }
+  }
+
+
+  // AFFIX PLUGIN DEFINITION
+  // =======================
+
+  function Plugin(option) {
+    return this.each(function () {
+      var $this   = $(this)
+      var data    = $this.data('bs.affix')
+      var options = typeof option == 'object' && option
+
+      if (!data) $this.data('bs.affix', (data = new Affix(this, options)))
+      if (typeof option == 'string') data[option]()
+    })
+  }
+
+  var old = $.fn.affix
+
+  $.fn.affix             = Plugin
+  $.fn.affix.Constructor = Affix
+
+
+  // AFFIX NO CONFLICT
+  // =================
+
+  $.fn.affix.noConflict = function () {
+    $.fn.affix = old
+    return this
+  }
+
+
+  // AFFIX DATA-API
+  // ==============
+
+  $(window).on('load', function () {
+    $('[data-spy="affix"]').each(function () {
+      var $spy = $(this)
+      var data = $spy.data()
+
+      data.offset = data.offset || {}
+
+      if (data.offsetBottom != null) data.offset.bottom = data.offsetBottom
+      if (data.offsetTop    != null) data.offset.top    = data.offsetTop
+
+      Plugin.call($spy, data)
+    })
+  })
+
+}(jQuery);

assets/_src/less/ascribe/_faq.less

@@ -71,8 +71,7 @@
 #toc {
     margin-top: @spacer;
     
-    &.sticky {
-        position: fixed;
+    &.affix {
         top: 0;
         padding-top: @spacer;
     }
@@ -117,3 +116,11 @@
         }
     }
 }
+
+
+//
+// Affix.js helpers
+//
+.affix {
+    position: fixed !important;
+}

content-main.php

@@ -18,7 +18,9 @@
 
         </div>
     <?php } else {
+
         echo $controller->loopSubtemplates();
+
     } ?>
 
 </main>