MDL-31052 Add generic lightbox spinner to indicate progress to user

lib/javascript-static.js

@@ -789,6 +789,49 @@ M.util.focus_login_form = function(Y) {
     }
 }
 
+/**
+ * Adds lightbox hidden element that covers the whole node.
+ *
+ * @param {YUI} Y
+ * @param {Node} the node lightbox should be added to
+ * @retun {Node} created lightbox node
+ */
+M.util.add_lightbox = function(Y, node) {
+    var WAITICON = {'pix':"i/loading_small",'component':'moodle'};
+
+    // Check if lightbox is already there
+    if (node.one('.lightbox')) {
+        return node.one('.lightbox');
+    }
+
+    node.setStyle('position', 'relative');
+    var waiticon = Y.Node.create('<img />')
+    .setAttrs({
+        'src' : M.util.image_url(WAITICON.pix, WAITICON.component)
+    })
+    .setStyles({
+        'position' : 'relative',
+        'top' : '50%'
+    });
+
+    var lightbox = Y.Node.create('<div></div>')
+    .setStyles({
+        'opacity' : '.75',
+        'position' : 'absolute',
+        'width' : '100%',
+        'height' : '100%',
+        'top' : 0,
+        'left' : 0,
+        'backgroundColor' : 'white',
+        'text-align' : 'center'
+    })
+    .setAttribute('class', 'lightbox')
+    .hide();
+
+    lightbox.appendChild(waiticon);
+    node.append(lightbox);
+    return lightbox;
+}
 
 //=== old legacy JS code, hopefully to be replaced soon by M.xx.yy and YUI3 code ===