Add scroll-to-top button for mobile advanced atlas

items_2.css

@@ -114,3 +114,26 @@
         margin: 0 0 14px;
     }
 }
+
+#scroll-up {
+    width: 10vw;
+    height: 10vw;
+    bottom: 4vw;
+    right: 4vw;
+    position: fixed;
+    display: none;
+    background-color: #212121;
+    font-size: 12pt;
+    font-weight: bold;
+    text-align: center;
+    line-height: 10vw;
+    border: 1px solid #666;
+    cursor: pointer;
+    user-select: none;
+}
+
+@media(max-width: 1099px) {
+    #scroll-up {
+        display: block;
+    }
+}

items_2.html

@@ -58,6 +58,7 @@
                 <div class="center" id="item-list-footer"></div>
             </div>
         </div>
+        <div id="scroll-up">&uparrow;</div>
         <script type="text/javascript" src="utils.js"></script>
         <script type="text/javascript" src="build_utils.js"></script>
         <script type="text/javascript" src="loadheader.js"></script>

items_2.js

@@ -404,6 +404,10 @@ function init_items2() {
     // focus the query filter text box
     searchFilterField.field.focus();
     searchFilterField.field.select();
+
+    // scroll-to-top button
+    document.getElementById('scroll-up')
+        .addEventListener('mousedown', e => scrollTo({ top: 0, behavior: 'smooth' }));
 }
 
 load_init(init_items2);