Added offsetTop feature

Author: vovayatsyuk

lib/web/mage/sticky.js

@@ -13,6 +13,7 @@ define([
         options: {
             container: '',
             spacingTop: 0,
+            offsetTop: 0,
             stickyClass: '_sticky'
         },
 
@@ -52,6 +53,22 @@ define([
 
                 offset = Math.max( 0, Math.min( offset, this.maxOffset) );
 
+                if (offset &&
+                    this.options.offsetTop &&
+                    !this.element.hasClass(this.options.stickyClass)) {
+
+                    var offsetTop = 0;
+                    if (typeof this.options.offsetTop === 'function') {
+                        offsetTop = this.options.offsetTop();
+                    } else {
+                        offsetTop = this.options.offsetTop;
+                    }
+
+                    if (offset < this.options.offsetTop) {
+                        offset = 0;
+                    }
+                }
+
                 this.element
                     .toggleClass(this.options.stickyClass, (offset > 0))
                     .css( 'top', offset );