ListView: Fix sticky group header overlapping top header

Controls/DataControls/DataControls.UWP/ListView/Model/LayoutController.cs

@@ -59,7 +59,11 @@ namespace Telerik.UI.Xaml.Controls.Data.ListView.Model
 
             this.strategy.RecycleAfterMeasure();
             this.model.View.ItemCheckBoxService.GenerateVisuals();
-            this.strategy.GenerateFrozenContainers();
+
+            if (this.ShouldGenerateFrozenContainers())
+            {
+                this.strategy.GenerateFrozenContainers();
+            }
 
             return resultSize;
         }
@@ -186,6 +190,26 @@ namespace Telerik.UI.Xaml.Controls.Data.ListView.Model
             this.owner.UpdateService.RegisterUpdate((int)UpdateFlags.AffectsContent);
         }
 
+        private bool ShouldGenerateFrozenContainers()
+        {
+            if (this.headerModel == null)
+            {
+                return true;
+            }
+
+            var layoutSlot = this.headerModel.LayoutSlot;
+            var scrollOffset = this.owner.ScrollOffset;
+
+            if (this.strategy.IsHorizontal)
+            {
+                return scrollOffset >= layoutSlot.Right;
+            }
+            else
+            {
+                return scrollOffset >= layoutSlot.Bottom;
+            }
+        }
+
         private RadSize MeasureHorizontal(RadSize newAvailableSize)
         {
             var measureConstraints = newAvailableSize;