From ceb2e386f45a1eb285840e74e1310d8107c0da4b Mon Sep 17 00:00:00 2001
From: PsychoMark <PsychoMark@users.noreply.github.com>
Date: Mon, 20 Jun 2016 14:20:55 +0200
Subject: [PATCH] Added missing ListBoxAutoScroll

---
 Infrastructure/ListBoxAutoScroll.cs | 135 ++++++++++++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100644 Infrastructure/ListBoxAutoScroll.cs

diff --git a/Infrastructure/ListBoxAutoScroll.cs b/Infrastructure/ListBoxAutoScroll.cs
new file mode 100644
index 0000000..3866c34
--- /dev/null
+++ b/Infrastructure/ListBoxAutoScroll.cs
@@ -0,0 +1,135 @@
+using System;
+using System.Collections;
+using System.Collections.Specialized;
+using System.Windows;
+using System.Windows.Data;
+using System.Windows.Controls;
+using System.Windows.Media;
+
+namespace PettingZoo.Infrastructure
+{
+    // Source: https://social.msdn.microsoft.com/Forums/vstudio/en-US/0f524459-b14e-4f9a-8264-267953418a2d/trivial-listboxlistview-autoscroll?forum=wpf
+    //
+    // Slightly modified version; takes into account the current scroll position of the ListBox,
+    // so the end user can scroll up without getting dragged down again.
+    public static class ListBox
+    {
+        public static readonly DependencyProperty AutoScrollProperty =
+            DependencyProperty.RegisterAttached("AutoScroll", typeof (bool), typeof (System.Windows.Controls.ListBox),
+                new PropertyMetadata(false));
+
+        public static readonly DependencyProperty AutoScrollHandlerProperty =
+            DependencyProperty.RegisterAttached("AutoScrollHandler", typeof (AutoScrollHandler),
+                typeof (System.Windows.Controls.ListBox));
+
+        public static bool GetAutoScroll(System.Windows.Controls.ListBox instance)
+        {
+            return (bool) instance.GetValue(AutoScrollProperty);
+        }
+
+        public static void SetAutoScroll(System.Windows.Controls.ListBox instance, bool value)
+        {
+            var oldHandler = (AutoScrollHandler) instance.GetValue(AutoScrollHandlerProperty);
+            if (oldHandler != null)
+            {
+                oldHandler.Dispose();
+                instance.SetValue(AutoScrollHandlerProperty, null);
+            }
+
+            instance.SetValue(AutoScrollProperty, value);
+            if (value)
+                instance.SetValue(AutoScrollHandlerProperty, new AutoScrollHandler(instance));
+        }
+    }
+
+
+    public class AutoScrollHandler : DependencyObject, IDisposable
+    {
+        public static readonly DependencyProperty ItemsSourceProperty =
+            DependencyProperty.Register("ItemsSource", typeof (IEnumerable),
+                typeof (AutoScrollHandler), new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.None,
+                    ItemsSourcePropertyChanged));
+
+        private readonly System.Windows.Controls.ListBox target;
+        private ScrollViewer scrollViewer = null;
+
+        public AutoScrollHandler(System.Windows.Controls.ListBox target)
+        {
+            this.target = target;
+
+            var binding = new Binding("ItemsSource")
+            {
+                Source = this.target
+            };
+
+            BindingOperations.SetBinding(this, ItemsSourceProperty, binding);
+        }
+
+
+        public void Dispose()
+        {
+            BindingOperations.ClearBinding(this, ItemsSourceProperty);
+        }
+
+
+        public IEnumerable ItemsSource
+        {
+            get { return (IEnumerable) GetValue(ItemsSourceProperty); }
+            set { SetValue(ItemsSourceProperty, value); }
+        }
+
+
+        private static void ItemsSourcePropertyChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
+        {
+            ((AutoScrollHandler) o).ItemsSourceChanged((IEnumerable) e.OldValue, (IEnumerable) e.NewValue);
+        }
+
+
+        private void ItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
+        {
+            var collection = oldValue as INotifyCollectionChanged;
+            if (collection != null)
+                collection.CollectionChanged -= Collection_CollectionChanged;
+
+            collection = newValue as INotifyCollectionChanged;
+            if (collection != null)
+                collection.CollectionChanged += Collection_CollectionChanged;
+        }
+
+        private void Collection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            if (e.Action != NotifyCollectionChangedAction.Add || e.NewItems == null || e.NewItems.Count < 1)
+                return;
+
+            // Resolve on demand; in the constructor FindScrollViewer will return null
+            if (scrollViewer == null)
+            {
+                scrollViewer = FindScrollViewer(target);
+                if (scrollViewer == null)
+                    return;
+            }
+
+            if (Math.Abs(scrollViewer.VerticalOffset - scrollViewer.ScrollableHeight) < 1)
+                target.ScrollIntoView(e.NewItems[e.NewItems.Count - 1]);
+        }
+
+
+        private static ScrollViewer FindScrollViewer(DependencyObject parent)
+        {
+            var childCount = VisualTreeHelper.GetChildrenCount(parent);
+            for (var childIndex = 0; childIndex < childCount; childIndex++)
+            {
+                var child = VisualTreeHelper.GetChild(parent, childIndex);
+                var scrollViewer = (child as ScrollViewer);
+                if (scrollViewer != null) 
+                    return scrollViewer;
+
+                scrollViewer = FindScrollViewer(child);
+                if (scrollViewer != null) 
+                    return scrollViewer;
+            }
+
+            return null;
+        }
+    }
+}