Bunch of changes for ItemsView and threads.

Wino.Mail.WinUI/Controls/Advanced/WinoItemsView.cs

@@ -1,14 +1,46 @@
 using System.Collections.Generic;
+using System.Windows.Input;
+using CommunityToolkit.WinUI;
 using Microsoft.UI.Xaml.Controls;
 
 namespace Wino.Mail.WinUI.Controls.Advanced;
 
 public partial class WinoItemsView : ItemsView
 {
+    private const string PART_ScrollView = nameof(PART_ScrollView);
+
+    private ScrollView? _internalScrollView;
+
+    [GeneratedDependencyProperty]
+    public partial ICommand LoadMoreCommand { get; set; }
+
     public IEnumerable<object>? CastedItemsSource => ItemsSource as IEnumerable<object>;
 
     public WinoItemsView()
     {
         DefaultStyleKey = typeof(ItemsView);
     }
+
+    protected override void OnApplyTemplate()
+    {
+        base.OnApplyTemplate();
+
+        _internalScrollView = GetTemplateChild("PART_ScrollView") as ScrollView ?? throw new System.Exception("Can't find the ScrollView in WinoItemsView.");
+
+        _internalScrollView.ViewChanged -= InternalScrollViewPositionChanged;
+        _internalScrollView.ViewChanged += InternalScrollViewPositionChanged;
+    }
+
+    private void InternalScrollViewPositionChanged(ScrollView sender, object args)
+    {
+        if (_internalScrollView == null) return;
+
+        // No need to raise init request if there are no items in the list.
+        if (ItemsSource == null) return;
+
+        double progress = sender.VerticalOffset / sender.ScrollableHeight;
+
+        // Trigger when scrolled past 90% of total height
+        if (progress >= 0.9) LoadMoreCommand?.Execute(null);
+    }
 }