adjust padding on fixed .topnav on modal show/hide, to remove the movement

hosting/static/hosting/js/initial.js

@@ -13,4 +13,44 @@ $( document ).ready(function() {
         }, 1000);
     });
 
+});
+
+function getScrollbarWidth() {
+    var outer = document.createElement("div");
+    outer.style.visibility = "hidden";
+    outer.style.width = "100px";
+    outer.style.msOverflowStyle = "scrollbar"; // needed for WinJS apps
+
+    document.body.appendChild(outer);
+
+    var widthNoScroll = outer.offsetWidth;
+    // force scrollbars
+    outer.style.overflow = "scroll";
+
+    // add innerdiv
+    var inner = document.createElement("div");
+    inner.style.width = "100%";
+    outer.appendChild(inner);
+
+    var widthWithScroll = inner.offsetWidth;
+
+    // remove divs
+    outer.parentNode.removeChild(outer);
+
+    return widthNoScroll - widthWithScroll;
+}
+
+// globally stores the width of scrollbar
+var scrollbarWidth = getScrollbarWidth();
+
+// add proper padding to fixed topnav on modal show
+$('body').on('click', '[data-toggle=modal]', function(){
+    var topnavPadding = parseInt($('.navbar-fixed-top.topnav').css('padding-right'));
+    $('.navbar-fixed-top.topnav').css('padding-right', topnavPadding+scrollbarWidth);
+});
+
+// remove added padding on modal hide
+$('body').on('hidden.bs.modal', function(){
+    var topnavPadding = parseInt($('.navbar-fixed-top.topnav').css('padding-right'));
+    $('.navbar-fixed-top.topnav').css('padding-right', topnavPadding-scrollbarWidth);
 });