From f5b27456ddb54bb8eae821a426d2c0e8c824a48b Mon Sep 17 00:00:00 2001
From: Kaniu Tayou <1056879522@qq.com>
Date: Thu, 20 Dec 2018 00:18:49 +0800
Subject: [PATCH] =?UTF-8?q?=E6=BB=9A=E5=8A=A8=E6=9D=A1?=
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---
 StormChatWPF/MainWindow.xaml     |  6 ++-
 StormChatWPF/ScrollViewer.cs     | 64 ++++++++++++++++++++++++++++++++
 StormChatWPF/StormChatWPF.csproj |  1 +
 3 files changed, 70 insertions(+), 1 deletion(-)
 create mode 100644 StormChatWPF/ScrollViewer.cs

diff --git a/StormChatWPF/MainWindow.xaml b/StormChatWPF/MainWindow.xaml
index 7c4c99a..74d527b 100644
--- a/StormChatWPF/MainWindow.xaml
+++ b/StormChatWPF/MainWindow.xaml
@@ -23,6 +23,10 @@
 		<ListView x:Name="UsersList" Margin="0,0,0,0" IsEnabled="True" SelectionChanged="UsersList_SelectionChanged" Grid.Row="1" Grid.RowSpan="2"/>
 		<TextBox x:Name="InputBox" Margin="0,0,0,0" TextWrapping="Wrap" Text="" Grid.Row="2" Grid.ColumnSpan="3" Grid.Column="1" />
 		<Button Content="Send" HorizontalAlignment="Right" Margin="0,0,0,0" VerticalAlignment="Bottom" Width="75" Click="Button_Click" Height="20" Grid.Row="2" Grid.Column="3"/>
-		<StackPanel x:Name="OutBox" Margin="0,0,0,0" Grid.ColumnSpan="3" Grid.Column="1" Grid.Row="1"/>
+		<ScrollViewer Grid.ColumnSpan="3" Grid.Column="1" Margin="0,0,0,0" Grid.Row="1" >
+			<ScrollViewer.Content>
+				<StackPanel x:Name="OutBox" Margin="0,0,0,0" Grid.ColumnSpan="3" Grid.Column="1" Grid.Row="1" ScrollViewer.VerticalScrollBarVisibility="Hidden"/>
+			</ScrollViewer.Content>
+		</ScrollViewer>
 	</Grid>
 </Window>
diff --git a/StormChatWPF/ScrollViewer.cs b/StormChatWPF/ScrollViewer.cs
new file mode 100644
index 0000000..3ff0a3d
--- /dev/null
+++ b/StormChatWPF/ScrollViewer.cs
@@ -0,0 +1,64 @@
+using System;
+using System.Windows;
+using System.Windows.Controls;
+
+namespace StormChatWPF
+{
+    public class ScrollViewerExtensions
+    {
+        public static readonly DependencyProperty AlwaysScrollToEndProperty = DependencyProperty.RegisterAttached("AlwaysScrollToEnd", typeof(bool), typeof(ScrollViewerExtensions), new PropertyMetadata(false, AlwaysScrollToEndChanged));
+        private static bool _autoScroll;
+
+
+        private static void AlwaysScrollToEndChanged(object sender, DependencyPropertyChangedEventArgs e)
+        {
+            ScrollViewer scroll = sender as ScrollViewer;
+            if (scroll != null)
+            {
+                bool alwaysScrollToEnd = (e.NewValue != null) && (bool)e.NewValue;
+                if (alwaysScrollToEnd)
+                {
+                    scroll.ScrollToEnd();
+                    scroll.ScrollChanged += ScrollChanged;
+                    // scroll.SizeChanged += Scroll_SizeChanged;
+                }
+                else { scroll.ScrollChanged -= ScrollChanged; /*scroll.ScrollChanged -= ScrollChanged; */}
+            }
+            else { throw new InvalidOperationException("The attached AlwaysScrollToEnd property can only be applied to ScrollViewer instances."); }
+        }
+
+
+        //private static void Scroll_SizeChanged(object sender, SizeChangedEventArgs e)
+        //{
+        //    ScrollViewer scroll = sender as ScrollViewer;
+        //    if (scroll == null) { throw new InvalidOperationException("The attached AlwaysScrollToEnd property can only be applied to ScrollViewer instances."); }
+        //    double d = scroll.ActualHeight + scroll.ViewportHeight + scroll.ExtentHeight;
+        //    scroll.ScrollToVerticalOffset(d);
+        //}
+
+
+        public static bool GetAlwaysScrollToEnd(ScrollViewer scroll)
+        {
+            if (scroll == null) { throw new ArgumentNullException("scroll"); }
+            return (bool)scroll.GetValue(AlwaysScrollToEndProperty);
+        }
+
+
+        public static void SetAlwaysScrollToEnd(ScrollViewer scroll, bool alwaysScrollToEnd)
+        {
+            if (scroll == null) { throw new ArgumentNullException("scroll"); }
+            scroll.SetValue(AlwaysScrollToEndProperty, alwaysScrollToEnd);
+        }
+
+
+        private static void ScrollChanged(object sender, ScrollChangedEventArgs e)
+        {
+            ScrollViewer scroll = sender as ScrollViewer;
+            if (scroll == null) { throw new InvalidOperationException("The attached AlwaysScrollToEnd property can only be applied to ScrollViewer instances."); }
+
+
+            if (e.ExtentHeightChange == 0) { _autoScroll = scroll.VerticalOffset == scroll.ScrollableHeight; }
+            if (_autoScroll && e.ExtentHeightChange != 0) { scroll.ScrollToVerticalOffset(scroll.ExtentHeight); }
+        }
+    }
+}
diff --git a/StormChatWPF/StormChatWPF.csproj b/StormChatWPF/StormChatWPF.csproj
index 08cf33d..ca29bee 100644
--- a/StormChatWPF/StormChatWPF.csproj
+++ b/StormChatWPF/StormChatWPF.csproj
@@ -63,6 +63,7 @@
     <Compile Include="MainWindow.xaml.cs">
       <DependentUpon>MainWindow.xaml</DependentUpon>
     </Compile>
+    <Compile Include="ScrollViewer.cs" />
     <Page Include="LogWindow.xaml">
       <Generator>MSBuild:Compile</Generator>
       <SubType>Designer</SubType>