Auto scroll when text changed or selection changed in a TextBox

SourceGit/Helpers/TextBoxHelper.cs

@@ -1,5 +1,6 @@
 using System.Windows;
 using System.Windows.Controls;
+using System.Windows.Input;
 using System.Windows.Media;
 
 namespace SourceGit.Helpers {
@@ -9,6 +10,15 @@ namespace SourceGit.Helpers {
     /// </summary>
     public static class TextBoxHelper {
 
+        /// <summary>
+        ///     Auto scroll on text changed.
+        /// </summary>
+        public static readonly DependencyProperty AutoScrollProperty = DependencyProperty.RegisterAttached(
+            "AutoScroll",
+            typeof(bool),
+            typeof(TextBoxHelper),
+            new PropertyMetadata(false, OnAutoScrollChanged));
+
         /// <summary>
         ///     Placeholder property  
         /// </summary>
@@ -36,6 +46,39 @@ namespace SourceGit.Helpers {
             typeof(TextBoxHelper),
             new PropertyMetadata(Brushes.Transparent));
 
+        /// <summary>
+        ///     Setter for AutoScrollProperty
+        /// </summary>
+        /// <param name="element"></param>
+        /// <param name="enabled"></param>
+        public static void SetAutoScroll(UIElement element, bool enabled) {
+            element.SetValue(AutoScrollProperty, enabled);
+        }
+
+        /// <summary>
+        ///     Getter for AutoScrollProperty
+        /// </summary>
+        /// <param name="element"></param>
+        /// <returns></returns>
+        public static bool GetAutoScroll(UIElement element) {
+            return (bool)element.GetValue(AutoScrollProperty);
+        }
+
+        /// <summary>
+        ///     Triggered when AutoScroll property changed.
+        /// </summary>
+        /// <param name="d"></param>
+        /// <param name="e"></param>
+        public static void OnAutoScrollChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
+            var textBox = d as TextBox;
+            if (textBox == null) return;
+
+            textBox.SelectionChanged -= UpdateScrollOnSelectionChanged;
+            if ((bool)e.NewValue == true) {
+                textBox.SelectionChanged += UpdateScrollOnSelectionChanged;
+            }
+        }
+
         /// <summary>
         ///     Triggered when placeholder changed.
         /// </summary>
@@ -122,8 +165,8 @@ namespace SourceGit.Helpers {
 
             textBox.SetValue(PlaceholderBrushProperty, brush);
             textBox.Background = brush;
-            textBox.TextChanged += OnTextChanged;
+            textBox.TextChanged += UpdatePlaceholder;
-            OnTextChanged(textBox, null);
+            UpdatePlaceholder(textBox, null);
         }
 
         /// <summary>
@@ -131,7 +174,7 @@ namespace SourceGit.Helpers {
         /// </summary>
         /// <param name="sender"></param>
         /// <param name="e"></param>
-        private static void OnTextChanged(object sender, RoutedEventArgs e) {
+        private static void UpdatePlaceholder(object sender, RoutedEventArgs e) {
             var textBox = sender as TextBox;
             if (string.IsNullOrEmpty(textBox.Text)) {
                 textBox.Background = textBox.GetValue(PlaceholderBrushProperty) as Brush;
@@ -139,5 +182,44 @@ namespace SourceGit.Helpers {
                 textBox.Background = Brushes.Transparent;
             }
         }
+
+        /// <summary>
+        ///     
+        /// </summary>
+        /// <param name="sender"></param>
+        /// <param name="e"></param>
+        private static void UpdateScrollOnSelectionChanged(object sender, RoutedEventArgs e) {
+            var textBox = sender as TextBox;
+            if (textBox != null && textBox.IsFocused) {
+                if (Mouse.LeftButton == MouseButtonState.Pressed && textBox.SelectionLength > 0) {
+                    var p = Mouse.GetPosition(textBox);
+                    if (p.X <= 8) {
+                        textBox.LineLeft();
+                    } else if (p.X >= textBox.ActualWidth - 8) {
+                        textBox.LineRight();
+                    }
+
+                    if (p.Y <= 8) {
+                        textBox.LineUp();
+                    } else if (p.Y >= textBox.ActualHeight - 8) {
+                        textBox.LineDown();
+                    }
+                } else {
+                    var rect = textBox.GetRectFromCharacterIndex(textBox.CaretIndex);
+                    if (rect.Left <= 0) {
+                        textBox.ScrollToHorizontalOffset(textBox.HorizontalOffset + rect.Left);
+                    } else if (rect.Right >= textBox.ActualWidth) {
+                        textBox.ScrollToHorizontalOffset(textBox.HorizontalOffset + rect.Right);
+                    }
+
+                    if (rect.Top <= 0) {
+                        textBox.ScrollToVerticalOffset(textBox.VerticalOffset + rect.Top);
+                    } else if (rect.Bottom >= textBox.ActualHeight) {
+                        textBox.ScrollToVerticalOffset(textBox.VerticalOffset + rect.Bottom);
+                    }
+                    
+                }
+            }
+        }
     }
 }

SourceGit/Resources/Styles/TextBox.xaml

@@ -1,5 +1,7 @@
 <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
-                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+                    xmlns:helpers="clr-namespace:SourceGit.Helpers">
+    
     <!-- 错误Tooltip -->
     <ControlTemplate x:Key="Template.Validation.Tooltip" TargetType="{x:Type ToolTip}">
         <Border x:Name="Root" Margin="5,0,0,0" Opacity="0" Padding="0,0,20,20" RenderTransformOrigin="0,0">
@@ -81,6 +83,7 @@
         <Setter Property="Background" Value="Transparent"/>
         <Setter Property="BorderBrush" Value="{DynamicResource Brush.Border1}"/>
         <Setter Property="Validation.ErrorTemplate" Value="{StaticResource Template.Validation.Error}"/>
+        <Setter Property="helpers:TextBoxHelper.AutoScroll" Value="True"/>
 
         <Setter Property="Template">
             <Setter.Value>
@@ -93,9 +96,10 @@
                         <ScrollViewer x:Name="PART_ContentHost"
                                       Margin="{TemplateBinding Padding}"
                                       VerticalAlignment="Center"
-                                      Background="{x:Null}"
+                                      Background="Transparent"
                                       BorderThickness="0"
                                       IsTabStop="False"
+                                      CanContentScroll="False"
                                       SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                     </Border>
                         

SourceGit/SourceGit.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
     <PropertyGroup>
-        <TargetFramework>net461</TargetFramework>
+        <TargetFramework>net46</TargetFramework>
         <OutputType>WinExe</OutputType>
         <UseWPF>true</UseWPF>
         <UseWindowsForms>true</UseWindowsForms>

SourceGit/UI/WorkingCopy.xaml

@@ -343,8 +343,7 @@
                 ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                 ScrollViewer.VerticalScrollBarVisibility="Auto"
                 helpers:TextBoxHelper.Placeholder="Enter commit message"
-                helpers:TextBoxHelper.PlaceholderBaseline="Top"
+                helpers:TextBoxHelper.PlaceholderBaseline="Top">
-                TextChanged="CommitMessageChanged">
                 <TextBox.Text>
                     <Binding ElementName="me" Path="CommitMessage" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged">
                         <Binding.ValidationRules>

SourceGit/UI/WorkingCopy.xaml.cs

@@ -729,10 +729,6 @@ namespace SourceGit.UI {
             e.Handled = true;
         }
 
-        private void CommitMessageChanged(object sender, TextChangedEventArgs e) {
-            (sender as TextBox).ScrollToEnd();
-        }
-
         private void StartAmend(object sender, RoutedEventArgs e) {
             var commits = Repo.Commits("-n 1");
             if (commits.Count == 0) {