refactor: rewrite TextDiffContext and fix the issue that text diff view does not navigate to the first change chunk after select a different commit with the same file

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/Commands/Diff.cs

@@ -21,7 +21,7 @@ public partial class Diff : Command
 
         public Diff(string repo, Models.DiffOption opt, int unified, bool ignoreWhitespace)
         {
-            _result.TextDiff = new Models.TextDiff() { Option = opt };
+            _result.TextDiff = new Models.TextDiff();
 
             WorkingDirectory = repo;
             Context = repo;

src/Models/DiffResult.cs

@@ -53,8 +53,6 @@ public class TextDiffSelection
 
     public partial class TextDiff
     {
-        public string File { get; set; } = string.Empty;
-        public DiffOption Option { get; set; } = null;
         public List<TextDiffLine> Lines { get; set; } = new List<TextDiffLine>();
         public int MaxLineNumber = 0;
 

src/ViewModels/DiffContext.cs

@@ -38,10 +38,7 @@ public bool ShowEntireFile
                     OnPropertyChanged();
 
                     if (Content is TextDiffContext ctx)
-                    {
-                        ctx.Data.File = string.Empty; // Just to ignore both previous `ScrollOffset` and `BlockNavigation`
                         LoadContent();
-                    }
                 }
             }
         }
@@ -156,7 +153,8 @@ private void LoadContent()
 
             Task.Run(async () =>
             {
-                var numLines = Preferences.Instance.UseFullTextDiff ? _entireFileLine : _unifiedLines;
+                var showEntireFile = Preferences.Instance.UseFullTextDiff;
+                var numLines = showEntireFile ? _entireFileLine : _unifiedLines;
                 var ignoreWhitespace = Preferences.Instance.IgnoreWhitespaceChangesInDiff;
 
                 var latest = await new Commands.Diff(_repo, _option, numLines, ignoreWhitespace)
@@ -200,10 +198,7 @@ private void LoadContent()
                     }
 
                     if (!isSubmodule)
-                    {
-                        latest.TextDiff.File = _option.Path;
                         rs = latest.TextDiff;
-                    }
                 }
                 else if (latest.IsBinary)
                 {
@@ -282,9 +277,9 @@ private void LoadContent()
                         IsTextDiff = true;
 
                         if (Preferences.Instance.UseSideBySideDiff)
-                            Content = new TwoSideTextDiff(cur, _content as TwoSideTextDiff);
+                            Content = new TwoSideTextDiff(_option, showEntireFile, cur, _content as TwoSideTextDiff);
                         else
-                            Content = new CombinedTextDiff(cur, _content as CombinedTextDiff);
+                            Content = new CombinedTextDiff(_option, showEntireFile, cur, _content as CombinedTextDiff);
                     }
                     else
                     {

src/ViewModels/TextDiffContext.cs

@@ -28,10 +28,8 @@ public static bool IsChanged(TextDiffSelectedChunk oldValue, TextDiffSelectedChu
 
     public class TextDiffContext : ObservableObject
     {
+        public Models.DiffOption Option => _option;
         public Models.TextDiff Data => _data;
-        public string File => _data.File;
-        public bool IsUnstaged => _data.Option.IsUnstaged;
-        public bool EnableChunkOption => _data.Option.WorkingCopyChange != null;
 
         public Vector ScrollOffset
         {
@@ -132,6 +130,30 @@ public virtual TextDiffContext SwitchMode()
             return null;
         }
 
+        protected bool TryKeepPrevScrollOffset(TextDiffContext prev)
+        {
+            var fastTest = prev != null &&
+                prev._showEntireFile == _showEntireFile &&
+                prev._option.IsUnstaged == _option.IsUnstaged &&
+                prev._option.Path.Equals(_option.Path, StringComparison.Ordinal) &&
+                prev._option.OrgPath.Equals(_option.OrgPath, StringComparison.Ordinal) &&
+                prev._option.Revisions.Count == _option.Revisions.Count;
+
+            if (!fastTest)
+                return false;
+
+            for (int i = 0; i < _option.Revisions.Count; i++)
+            {
+                if (!prev._option.Revisions[i].Equals(_option.Revisions[i], StringComparison.Ordinal))
+                    return false;
+            }
+
+            _scrollOffset = prev._scrollOffset;
+            return true;
+        }
+
+        protected Models.DiffOption _option = null;
+        protected bool _showEntireFile = false;
         protected Models.TextDiff _data = null;
         protected Vector _scrollOffset = Vector.Zero;
         protected BlockNavigation _blockNavigation = null;
@@ -142,24 +164,19 @@ public virtual TextDiffContext SwitchMode()
 
     public class CombinedTextDiff : TextDiffContext
     {
-        public CombinedTextDiff(Models.TextDiff diff, CombinedTextDiff previous = null)
+        public CombinedTextDiff(Models.DiffOption option, bool showEntireFile, Models.TextDiff diff, CombinedTextDiff previous = null)
         {
+            _option = option;
+            _showEntireFile = showEntireFile;
             _data = diff;
 
-            if (previous != null && previous.File.Equals(File, StringComparison.Ordinal))
-            {
-                _blockNavigation = new BlockNavigation(_data.Lines, false);
-                _scrollOffset = previous._scrollOffset;
-            }
-            else
-            {
-                _blockNavigation = new BlockNavigation(_data.Lines, true);
-            }
+            var keep = TryKeepPrevScrollOffset(previous);
+            _blockNavigation = new BlockNavigation(_data.Lines, !keep);
         }
 
         public override TextDiffContext SwitchMode()
         {
-            return new TwoSideTextDiff(_data);
+            return new TwoSideTextDiff(_option, _showEntireFile, _data);
         }
     }
 
@@ -168,8 +185,10 @@ public class TwoSideTextDiff : TextDiffContext
         public List<Models.TextDiffLine> Old { get; } = [];
         public List<Models.TextDiffLine> New { get; } = [];
 
-        public TwoSideTextDiff(Models.TextDiff diff, TwoSideTextDiff previous = null)
+        public TwoSideTextDiff(Models.DiffOption option, bool showEntireFile, Models.TextDiff diff, TwoSideTextDiff previous = null)
         {
+            _option = option;
+            _showEntireFile = showEntireFile;
             _data = diff;
 
             foreach (var line in diff.Lines)
@@ -192,15 +211,8 @@ public TwoSideTextDiff(Models.TextDiff diff, TwoSideTextDiff previous = null)
 
             FillEmptyLines();
 
-            if (previous != null && previous.File.Equals(File, StringComparison.Ordinal))
-            {
-                _blockNavigation = new BlockNavigation(Old, false);
-                _scrollOffset = previous._scrollOffset;
-            }
-            else
-            {
-                _blockNavigation = new BlockNavigation(Old, true);
-            }
+            var keep = TryKeepPrevScrollOffset(previous);
+            _blockNavigation = new BlockNavigation(Old, !keep);
         }
 
         public override bool IsSideBySide()
@@ -210,7 +222,7 @@ public override bool IsSideBySide()
 
         public override TextDiffContext SwitchMode()
         {
-            return new CombinedTextDiff(_data);
+            return new CombinedTextDiff(_option, _showEntireFile, _data);
         }
 
         public void ConvertsToCombinedRange(ref int startLine, ref int endLine, bool isOldSide)

src/Views/TextDiffView.axaml

@@ -14,7 +14,7 @@
         <DataTemplate DataType="vm:CombinedTextDiff">
           <Grid ColumnDefinitions="*,1,12">
             <v:CombinedTextDiffPresenter Grid.Column="0"
-                                         FileName="{Binding File}"
+                                         FileName="{Binding Option.Path}"
                                          Foreground="{DynamicResource Brush.FG1}"
                                          LineBrush="{DynamicResource Brush.Border2}"
                                          EmptyContentBackground="{DynamicResource Brush.Diff.EmptyBG}"
@@ -29,7 +29,6 @@
                                          UseSyntaxHighlighting="{Binding Source={x:Static vm:Preferences.Instance}, Path=UseSyntaxHighlighting}"
                                          WordWrap="{Binding Source={x:Static vm:Preferences.Instance}, Path=EnableDiffViewWordWrap}"
                                          ShowHiddenSymbols="{Binding Source={x:Static vm:Preferences.Instance}, Path=ShowHiddenSymbolsInDiffView}"
-                                         EnableChunkSelection="{Binding EnableChunkOption}"
                                          SelectedChunk="{Binding SelectedChunk, Mode=TwoWay}"
                                          BlockNavigation="{Binding BlockNavigation, Mode=OneWay}"/>
 
@@ -46,7 +45,7 @@
           <Grid ColumnDefinitions="*,1,*,1,12">
             <v:SingleSideTextDiffPresenter Grid.Column="0"
                                            IsOld="True"
-                                           FileName="{Binding File}"
+                                           FileName="{Binding Option.Path}"
                                            Foreground="{DynamicResource Brush.FG1}"
                                            LineBrush="{DynamicResource Brush.Border2}"
                                            EmptyContentBackground="{DynamicResource Brush.Diff.EmptyBG}"
@@ -61,15 +60,14 @@
                                            UseSyntaxHighlighting="{Binding Source={x:Static vm:Preferences.Instance}, Path=UseSyntaxHighlighting}"
                                            WordWrap="False"
                                            ShowHiddenSymbols="{Binding Source={x:Static vm:Preferences.Instance}, Path=ShowHiddenSymbolsInDiffView}"
-                                           EnableChunkSelection="{Binding EnableChunkOption, Mode=OneWay}"
                                            SelectedChunk="{Binding SelectedChunk, Mode=TwoWay}"
                                            BlockNavigation="{Binding BlockNavigation, Mode=OneWay}"/>
 
             <Rectangle Grid.Column="1" Fill="{DynamicResource Brush.Border2}" Width="1" HorizontalAlignment="Center" VerticalAlignment="Stretch"/>
 
             <v:SingleSideTextDiffPresenter Grid.Column="2"
                                            IsOld="False"
-                                           FileName="{Binding File}"
+                                           FileName="{Binding Option.Path}"
                                            Foreground="{DynamicResource Brush.FG1}"
                                            LineBrush="{DynamicResource Brush.Border2}"
                                            EmptyContentBackground="{DynamicResource Brush.Diff.EmptyBG}"
@@ -84,7 +82,6 @@
                                            UseSyntaxHighlighting="{Binding Source={x:Static vm:Preferences.Instance}, Path=UseSyntaxHighlighting}"
                                            WordWrap="False"
                                            ShowHiddenSymbols="{Binding Source={x:Static vm:Preferences.Instance}, Path=ShowHiddenSymbolsInDiffView}"
-                                           EnableChunkSelection="{Binding EnableChunkOption, Mode=OneWay}"
                                            SelectedChunk="{Binding SelectedChunk, Mode=TwoWay}"
                                            BlockNavigation="{Binding BlockNavigation, Mode=OneWay}"/>
 
@@ -100,7 +97,7 @@
     </ContentControl>
 
     <StackPanel x:Name="Popup" IsVisible="False" Orientation="Horizontal" VerticalAlignment="Top" HorizontalAlignment="Right" Effect="drop-shadow(0 0 8 #80000000)">
-      <Button Classes="flat" Click="OnStageChunk" HotKey="{OnPlatform Ctrl+S, macOS=⌘+S}" IsVisible="{Binding IsUnstaged}">
+      <Button Classes="flat" Click="OnStageChunk" HotKey="{OnPlatform Ctrl+S, macOS=⌘+S}" IsVisible="{Binding Option.IsUnstaged}">
         <TextBlock>
           <Run Text="{DynamicResource Text.Hunk.Stage}"/>
           <Run Text=" "/>
@@ -111,7 +108,7 @@
         </TextBlock>
       </Button>
 
-      <Button Classes="flat" Click="OnUnstageChunk" HotKey="{OnPlatform Ctrl+U, macOS=⌘+U}" IsVisible="{Binding IsUnstaged, Converter={x:Static BoolConverters.Not}}">
+      <Button Classes="flat" Click="OnUnstageChunk" HotKey="{OnPlatform Ctrl+U, macOS=⌘+U}" IsVisible="{Binding Option.IsUnstaged, Converter={x:Static BoolConverters.Not}}">
         <TextBlock>
           <Run Text="{DynamicResource Text.Hunk.Unstage}"/>
           <Run Text=" "/>
@@ -122,7 +119,7 @@
         </TextBlock>
       </Button>
 
-      <Button Classes="flat" Margin="8,0,0,0" HotKey="{OnPlatform Ctrl+D, macOS=⌘+D}" Click="OnDiscardChunk" IsVisible="{Binding IsUnstaged}">
+      <Button Classes="flat" Margin="8,0,0,0" HotKey="{OnPlatform Ctrl+D, macOS=⌘+D}" Click="OnDiscardChunk" IsVisible="{Binding Option.IsUnstaged}">
         <TextBlock>
           <Run Text="{DynamicResource Text.Hunk.Discard}"/>
           <Run Text=" "/>