DOC: modify theme css to keep navigation fixed on screen

Author: y-p

doc/source/themes/nature_with_gtoc/layout.html

@@ -66,4 +66,28 @@ <h3 style="margin-top: 1.5em;">{{ _('Search') }}</h3>
         </div>
     </div>
 </div>
+
+<script type="text/javascript">
+    // http://movethewebforward.org/
+    // paul irish et al. we <3 you.
+    var $body = $( document.body );
+
+    var $scrollable = $(window); // default scrollable thingy, which'll be body or docEl (html)
+    $originalnavtop =52; //$scrollable.css('top');
+
+    // work on scroll, but debounced
+    var $document = $(document).scroll( function() {
+        var $nav = $("div.sphinxsidebar");
+        if($scrollable.scrollTop() > ($originalnavtop - 20)) {
+            $nav.addClass('sticky').css('top', '0');
+            $nav.addClass('sticky').css('position', 'fixed');
+        } else {
+            $nav.removeClass('sticky');
+            $nav.addClass('sticky').css('position', '');
+            $nav.addClass('sticky').css('top', '');
+        }
+
+    });
+</script>
+
 {%- endblock %}

doc/source/themes/nature_with_gtoc/static/nature.css_t

@@ -79,7 +79,7 @@ div.sphinxsidebar {
   width: {{ theme_sidebarwidth|toint }}px;
   margin: 0 ;
   float: left;
-
+  /*position: fixed;*/
   background-color: #eee;
 }
 /*