feature: allow user to control whether or not to enable syntax highlighting in DiffView.

src/SourceGit/Resources/Icons.axaml

@@ -85,4 +85,5 @@
   <StreamGeometry x:Key="Icons.Statistics">M296 912H120c-4.4 0-8-3.6-8-8V520c0-4.4 3.6-8 8-8h176c4.4 0 8 3.6 8 8v384c0 4.4-3.6 8-8 8zM600 912H424c-4.4 0-8-3.6-8-8V121c0-4.4 3.6-8 8-8h176c4.4 0 8 3.6 8 8v783c0 4.4-3.6 8-8 8zM904 912H728c-4.4 0-8-3.6-8-8V280c0-4.4 3.6-8 8-8h176c4.4 0 8 3.6 8 8v624c0 4.4-3.6 8-8 8z</StreamGeometry>
   <StreamGeometry x:Key="Icons.Hotkeys">M512 0C229.216 0 0 229.216 0 512c0 282.752 229.216 512 512 512s512-229.248 512-512c0-282.784-229.216-512-512-512z m0 957.92C266.112 957.92 66.08 757.888 66.08 512S266.112 66.08 512 66.08 957.92 266.112 957.92 512 757.888 957.92 512 957.92zM192 416h96a32 32 0 0 0 32-32v-32a32 32 0 0 0-32-32H192a32 32 0 0 0-32 32v32a32 32 0 0 0 32 32zM384 416h96a32 32 0 0 0 32-32v-32a32 32 0 0 0-32-32h-96a32 32 0 0 0-32 32v32a32 32 0 0 0 32 32zM576 416h96a32 32 0 0 0 32-32v-32a32 32 0 0 0-32-32h-96a32 32 0 0 0-32 32v32a32 32 0 0 0 32 32zM832 320h-64a32 32 0 0 0-32 32v128h-160a32 32 0 0 0-32 32v32a32 32 0 0 0 32 32h256a32 32 0 0 0 32-32v-192a32 32 0 0 0-32-32zM320 544v-32a32 32 0 0 0-32-32H192a32 32 0 0 0-32 32v32a32 32 0 0 0 32 32h96a32 32 0 0 0 32-32zM384 576h96a32 32 0 0 0 32-32v-32a32 32 0 0 0-32-32h-96a32 32 0 0 0-32 32v32a32 32 0 0 0 32 32zM800 640H256a32 32 0 0 0-32 32v32a32 32 0 0 0 32 32h544a32 32 0 0 0 32-32v-32a32 32 0 0 0-32-32z</StreamGeometry>
   <StreamGeometry x:Key="Icons.SideBySide">M875 117H149C109 117 75 151 75 192v640c0 41 34 75 75 75h725c41 0 75-34 75-75V192c0-41-34-75-75-75zM139 832V192c0-6 4-11 11-11h331v661H149c-6 0-11-4-11-11zm747 0c0 6-4 11-11 11H544v-661H875c6 0 11 4 11 11v640z</StreamGeometry>
+  <StreamGeometry x:Key="Icons.SyntaxHighlight">M875 128h-725A107 107 0 0043 235v555A107 107 0 00149 896h725a107 107 0 00107-107v-555A107 107 0 00875 128zm-115 640h-183v-58l25-3c15 0 19-8 14-24l-22-61H419l-28 82 39 2V768h-166v-58l18-3c18-2 22-11 26-24l125-363-40-4V256h168l160 448 39 3zM506 340l-72 218h145l-71-218h-2z</StreamGeometry>
 </ResourceDictionary>

src/SourceGit/Resources/Locales.Designer.cs

@@ -1284,6 +1284,15 @@ namespace SourceGit.Resources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Syntax Highlighting.
+        /// </summary>
+        public static string Text_Diff_SyntaxHighlight {
+            get {
+                return ResourceManager.GetString("Text.Diff.SyntaxHighlight", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Open With Merge Tool.
         /// </summary>

src/SourceGit/Resources/Locales.en.resx

@@ -1287,4 +1287,7 @@
   <data name="Text.Cut" xml:space="preserve">
     <value>Cut</value>
   </data>
+  <data name="Text.Diff.SyntaxHighlight" xml:space="preserve">
+    <value>Syntax Highlighting</value>
+  </data>
 </root>

src/SourceGit/Resources/Locales.resx

@@ -1287,4 +1287,7 @@
   <data name="Text.Cut" xml:space="preserve">
     <value>Cut</value>
   </data>
+  <data name="Text.Diff.SyntaxHighlight" xml:space="preserve">
+    <value>Syntax Highlighting</value>
+  </data>
 </root>

src/SourceGit/Resources/Locales.zh.resx

@@ -1287,4 +1287,7 @@
   <data name="Text.Cut" xml:space="preserve">
     <value>剪切</value>
   </data>
+  <data name="Text.Diff.SyntaxHighlight" xml:space="preserve">
+    <value>语法高亮</value>
+  </data>
 </root>

src/SourceGit/ViewModels/Preference.cs

@@ -114,6 +114,12 @@ namespace SourceGit.ViewModels
             set => SetProperty(ref _useSideBySideDiff, value);
         }
 
+        public bool UseSyntaxHighlighting
+        {
+            get => _useSyntaxHighlighting;
+            set => SetProperty(ref _useSyntaxHighlighting, value);
+        }
+
         public Models.ChangeViewMode UnstagedChangeViewMode
         {
             get => _unstagedChangeViewMode;
@@ -351,6 +357,7 @@ namespace SourceGit.ViewModels
         private bool _useFixedTabWidth = true;
         private bool _useTwoColumnsLayoutInHistories = false;
         private bool _useSideBySideDiff = false;
+        private bool _useSyntaxHighlighting = false;
 
         private Models.ChangeViewMode _unstagedChangeViewMode = Models.ChangeViewMode.List;
         private Models.ChangeViewMode _stagedChangeViewMode = Models.ChangeViewMode.List;

src/SourceGit/Views/DiffView.axaml

@@ -27,13 +27,22 @@
           </StackPanel>
 
           <StackPanel Grid.Column="2" Margin="32,0,0,0" Orientation="Horizontal" IsVisible="{Binding IsTextDiff}" VerticalAlignment="Center">
+            <ToggleButton Classes="line_path"
+                          Width="32" Height="18"
+                          Background="Transparent"
+                          Padding="9,6"
+                          IsChecked="{Binding Source={x:Static vm:Preference.Instance}, Path=UseSyntaxHighlighting, Mode=TwoWay}"
+                          ToolTip.Tip="{DynamicResource Text.Diff.SyntaxHighlight}">
+              <Path Width="13" Height="13" Data="{StaticResource Icons.SyntaxHighlight}" Margin="0,3,0,0"/>
+            </ToggleButton>
+
             <ToggleButton Classes="line_path"
                           Width="32" Height="18"
                           Background="Transparent"
                           Padding="9,6"
                           IsChecked="{Binding Source={x:Static vm:Preference.Instance}, Path=UseSideBySideDiff, Mode=TwoWay}"
                           ToolTip.Tip="{DynamicResource Text.Diff.SideBySide}">
-              <Path Width="12" Height="12" Data="{StaticResource Icons.SideBySide}"/>
+              <Path Width="12" Height="12" Data="{StaticResource Icons.SideBySide}" Margin="0,2,0,0"/>
             </ToggleButton>
             
             <Button Classes="icon_button" Width="32" Command="{Binding OpenExternalMergeTool}" ToolTip.Tip="{DynamicResource Text.Diff.UseMerger}">

src/SourceGit/Views/TextDiffView.axaml

@@ -20,13 +20,15 @@
                                    FontFamily="fonts:SourceGit#JetBrains Mono"
                                    FontSize="12"
                                    DiffData="{Binding}"
-                                   SyncScrollOffset="{Binding $parent[v:DiffView].DataContext.(vm:DiffContext).SyncScrollOffset, Mode=TwoWay}"/>
+                                   SyncScrollOffset="{Binding $parent[v:DiffView].DataContext.(vm:DiffContext).SyncScrollOffset, Mode=TwoWay}"
+                                   UseSyntaxHighlighting="{Binding Source={x:Static vm:Preference.Instance}, Path=UseSyntaxHighlighting, Mode=TwoWay}"/>
     </DataTemplate>
 
     <DataTemplate DataType="vm:TwoSideTextDiff">
       <Grid ColumnDefinitions="*,1,*">
         <v:SingleSideTextDiffPresenter Grid.Column="0"
                                        SyncScrollOffset="{Binding $parent[v:DiffView].DataContext.(vm:DiffContext).SyncScrollOffset, Mode=TwoWay}"
+                                       UseSyntaxHighlighting="{Binding Source={x:Static vm:Preference.Instance}, Path=UseSyntaxHighlighting, Mode=TwoWay}"
                                        IsOld="True"
                                        HorizontalScrollBarVisibility="Auto"
                                        VerticalScrollBarVisibility="Auto"
@@ -42,6 +44,7 @@
 
         <v:SingleSideTextDiffPresenter Grid.Column="2"
                                        SyncScrollOffset="{Binding $parent[v:DiffView].DataContext.(vm:DiffContext).SyncScrollOffset, Mode=TwoWay}"
+                                       UseSyntaxHighlighting="{Binding Source={x:Static vm:Preference.Instance}, Path=UseSyntaxHighlighting, Mode=TwoWay}"
                                        IsOld="False"
                                        HorizontalScrollBarVisibility="Auto"
                                        VerticalScrollBarVisibility="Auto"

src/SourceGit/Views/TextDiffView.axaml.cs

@@ -224,6 +224,15 @@ namespace SourceGit.Views
             set => SetValue(SyncScrollOffsetProperty, value);
         }
 
+        public static readonly StyledProperty<bool> UseSyntaxHighlightingProperty =
+            AvaloniaProperty.Register<SingleSideTextDiffPresenter, bool>(nameof(UseSyntaxHighlighting), false);
+
+        public bool UseSyntaxHighlighting
+        {
+            get => GetValue(UseSyntaxHighlightingProperty);
+            set => SetValue(UseSyntaxHighlightingProperty, value);
+        }
+
         protected override Type StyleKeyOverride => typeof(TextEditor);
 
         public CombinedTextDiffPresenter() : base(new TextArea(), new TextDocument())
@@ -241,16 +250,15 @@ namespace SourceGit.Views
 
             TextArea.TextView.Margin = new Thickness(4, 0);
             TextArea.TextView.BackgroundRenderers.Add(new LineBackgroundRenderer(this));
+            TextArea.TextView.LineTransformers.Add(_lineStyleTransformer);
         }
 
         protected override void OnLoaded(RoutedEventArgs e)
         {
             base.OnLoaded(e);
 
-            _textMate = Models.TextMateHelper.CreateForEditor(this);
+            UpdateTextMate();
-            if (DiffData != null) Models.TextMateHelper.SetGrammarByFileName(_textMate, DiffData.File);
 
-            TextArea.TextView.LineTransformers.Add(_lineStyleTransformer);
             TextArea.TextView.ContextRequested += OnTextViewContextRequested;
             TextArea.TextView.ScrollOffsetChanged += OnTextViewScrollOffsetChanged;
         }
@@ -259,7 +267,6 @@ namespace SourceGit.Views
         {
             base.OnUnloaded(e);
 
-            TextArea.TextView.LineTransformers.Remove(_lineStyleTransformer);
             TextArea.TextView.ContextRequested -= OnTextViewContextRequested;
             TextArea.TextView.ScrollOffsetChanged -= OnTextViewScrollOffsetChanged;
 
@@ -333,12 +340,42 @@ namespace SourceGit.Views
                     scrollable.Offset = SyncScrollOffset;
                 }
             }
+            else if (change.Property == UseSyntaxHighlightingProperty)
+            {
+                UpdateTextMate();
+            }
             else if (change.Property.Name == "ActualThemeVariant" && change.NewValue != null)
             {
                 Models.TextMateHelper.SetThemeByApp(_textMate);
             }
         }
 
+        private void UpdateTextMate()
+        {
+            if (UseSyntaxHighlighting)
+            {
+                if (_textMate == null)
+                {
+                    TextArea.TextView.LineTransformers.Remove(_lineStyleTransformer);
+                    _textMate = Models.TextMateHelper.CreateForEditor(this);
+                    TextArea.TextView.LineTransformers.Add(_lineStyleTransformer);
+
+                    if (DiffData != null) Models.TextMateHelper.SetGrammarByFileName(_textMate, DiffData.File);
+                }
+            }
+            else
+            {
+                if (_textMate != null)
+                {
+                    _textMate.Dispose();
+                    _textMate = null;
+                    GC.Collect();
+
+                    TextArea.TextView.Redraw();
+                }
+            }
+        }
+
         private TextMate.Installation _textMate;
         private LineStyleTransformer _lineStyleTransformer = null;
     }
@@ -557,6 +594,15 @@ namespace SourceGit.Views
             set => SetValue(SyncScrollOffsetProperty, value);
         }
 
+        public static readonly StyledProperty<bool> UseSyntaxHighlightingProperty =
+            AvaloniaProperty.Register<SingleSideTextDiffPresenter, bool>(nameof(UseSyntaxHighlighting), false);
+
+        public bool UseSyntaxHighlighting
+        {
+            get => GetValue(UseSyntaxHighlightingProperty);
+            set => SetValue(UseSyntaxHighlightingProperty, value);
+        }
+
         protected override Type StyleKeyOverride => typeof(TextEditor);
 
         public SingleSideTextDiffPresenter() : base(new TextArea(), new TextDocument())
@@ -571,6 +617,7 @@ namespace SourceGit.Views
             TextArea.LeftMargins.Add(new VerticalSeperatorMargin(this));
             TextArea.TextView.Margin = new Thickness(4, 0);
             TextArea.TextView.BackgroundRenderers.Add(new LineBackgroundRenderer(this));
+            TextArea.TextView.LineTransformers.Add(_lineStyleTransformer);
         }
 
         protected override void OnLoaded(RoutedEventArgs e)
@@ -584,10 +631,8 @@ namespace SourceGit.Views
                 _scrollViewer.ScrollChanged += OnTextViewScrollChanged;
             }
 
-            _textMate = Models.TextMateHelper.CreateForEditor(this);
+            UpdateTextMate();
-            if (DiffData != null) Models.TextMateHelper.SetGrammarByFileName(_textMate, DiffData.File);
 
-            TextArea.TextView.LineTransformers.Add(_lineStyleTransformer);
             TextArea.TextView.ContextRequested += OnTextViewContextRequested;
         }
 
@@ -607,7 +652,6 @@ namespace SourceGit.Views
                 _textMate = null;
             }
 
-            TextArea.TextView.LineTransformers.Remove(_lineStyleTransformer);
             TextArea.TextView.ContextRequested -= OnTextViewContextRequested;
 
             GC.Collect();
@@ -703,12 +747,42 @@ namespace SourceGit.Views
                     }
                 }
             }
+            else if (change.Property == UseSyntaxHighlightingProperty)
+            {
+                UpdateTextMate();
+            }
             else if (change.Property.Name == "ActualThemeVariant" && change.NewValue != null)
             {
                 Models.TextMateHelper.SetThemeByApp(_textMate);
             }
         }
 
+        private void UpdateTextMate()
+        {
+            if (UseSyntaxHighlighting)
+            {
+                if (_textMate == null)
+                {
+                    TextArea.TextView.LineTransformers.Remove(_lineStyleTransformer);
+                    _textMate = Models.TextMateHelper.CreateForEditor(this);
+                    TextArea.TextView.LineTransformers.Add(_lineStyleTransformer);
+
+                    if (DiffData != null) Models.TextMateHelper.SetGrammarByFileName(_textMate, DiffData.File);
+                }
+            }
+            else
+            {
+                if (_textMate != null)
+                {
+                    _textMate.Dispose();
+                    _textMate = null;
+                    GC.Collect();
+
+                    TextArea.TextView.Redraw();
+                }
+            }
+        }
+
         private TextMate.Installation _textMate;
         private LineStyleTransformer _lineStyleTransformer = null;
         private ScrollViewer _scrollViewer = null;