Add navigation and highlighting of change-blocks in Text Diff (#616, #717) (#703)

* Corrected misspelled local variable nextHigh(t)light

* Implemented change-block navigation

* Modified behavior of the Prev/Next Change buttons in DiffView toolbar.
* Well-defined change-blocks are pre-calculated and can be navigated between.
* Current change-block is highlighted in the Diff panel(s).
* Prev/next at start/end of range (re-)scrolls to first/last change-block
(I.e when unset, or already at first/last change-block, or at the only one.)
* Current change-block is unset in RefreshContent().

* Added safeguards for edge cases

* Added indicator of current/total change-blocks in DiffView toolbar

* Added new Icon and String (en-US) for Highlighted Diff Navigation

* Added Preference and ToggleButton for diff navigation style

Author: goran-w

src/Commands/Diff.cs

@@ -51,6 +51,9 @@ public Models.DiffResult Result()
                     _result.TextDiff.MaxLineNumber = Math.Max(_newLine, _oldLine);
             }
 
+            if (_result.TextDiff != null)
+                _result.TextDiff.ProcessChangeBlocks();
+
             return _result;
         }
 

src/Models/DiffResult.cs

@@ -2,6 +2,8 @@
 using System.Text;
 using System.Text.RegularExpressions;
 
+using CommunityToolkit.Mvvm.ComponentModel;
+
 using Avalonia;
 using Avalonia.Media.Imaging;
 
@@ -59,16 +61,70 @@ public bool IsInRange(int idx)
         }
     }
 
-    public partial class TextDiff
+    public class TextDiffChangeBlock
+    {
+        public TextDiffChangeBlock(int startLine, int endLine)
+        {
+            StartLine = startLine;
+            EndLine = endLine;
+        }
+
+        public int StartLine { get; set; } = 0;
+        public int EndLine { get; set; } = 0;
+
+        public bool IsInRange(int line)
+        {
+            return line >= StartLine && line <= EndLine;
+        }
+    }
+
+    public partial class TextDiff : ObservableObject
     {
         public string File { get; set; } = string.Empty;
         public List<TextDiffLine> Lines { get; set; } = new List<TextDiffLine>();
         public Vector ScrollOffset { get; set; } = Vector.Zero;
         public int MaxLineNumber = 0;
 
+        public int CurrentChangeBlockIdx
+        {
+            get => _currentChangeBlockIdx;
+            set => SetProperty(ref _currentChangeBlockIdx, value);
+        }
+
         public string Repo { get; set; } = null;
         public DiffOption Option { get; set; } = null;
 
+        public List<TextDiffChangeBlock> ChangeBlocks { get; set; } = [];
+
+        public void ProcessChangeBlocks()
+        {
+            ChangeBlocks.Clear();
+            int lineIdx = 0, blockStartIdx = 0;
+            bool isNewBlock = true;
+            foreach (var line in Lines)
+            {
+                lineIdx++;
+                if (line.Type == Models.TextDiffLineType.Added ||
+                    line.Type == Models.TextDiffLineType.Deleted ||
+                    line.Type == Models.TextDiffLineType.None) // Empty
+                {
+                    if (isNewBlock)
+                    {
+                        isNewBlock = false;
+                        blockStartIdx = lineIdx;
+                    }
+                }
+                else
+                {
+                    if (!isNewBlock)
+                    {
+                        ChangeBlocks.Add(new TextDiffChangeBlock(blockStartIdx, lineIdx - 1));
+                        isNewBlock = true;
+                    }
+                }
+            }
+        }
+
         public TextDiffSelection MakeSelection(int startLine, int endLine, bool isCombined, bool isOldSide)
         {
             var rs = new TextDiffSelection();
@@ -626,6 +682,8 @@ private bool ProcessIndicatorForPatchSingleSide(StringBuilder builder, TextDiffL
             return true;
         }
 
+        private int _currentChangeBlockIdx = -1; // NOTE: Use -1 as "not set".
+
         [GeneratedRegex(@"^@@ \-(\d+),?\d* \+(\d+),?\d* @@")]
         private static partial Regex REG_INDICATOR();
     }

src/Resources/Icons.axaml

@@ -54,6 +54,7 @@
   <StreamGeometry x:Key="Icons.Grid">M30 271l241 0 0-241-241 0 0 241zM392 271l241 0 0-241-241 0 0 241zM753 30l0 241 241 0 0-241-241 0zM30 632l241 0 0-241-241 0 0 241zM392 632l241 0 0-241-241 0 0 241zM753 632l241 0 0-241-241 0 0 241zM30 994l241 0 0-241-241 0 0 241zM392 994l241 0 0-241-241 0 0 241zM753 994l241 0 0-241-241 0 0 241z</StreamGeometry>
   <StreamGeometry x:Key="Icons.Head">M0 512M1024 512M512 0M512 1024M955 323q0 23-16 39l-414 414-78 78q-16 16-39 16t-39-16l-78-78-207-207q-16-16-16-39t16-39l78-78q16-16 39-16t39 16l168 169 375-375q16-16 39-16t39 16l78 78q16 16 16 39z</StreamGeometry>
   <StreamGeometry x:Key="Icons.HiddenSymbol">M416 64H768v64h-64v704h64v64H448v-64h64V512H416a224 224 0 1 1 0-448zM576 832h64V128H576v704zM416 128H512v320H416a160 160 0 0 1 0-320z</StreamGeometry>
+  <StreamGeometry x:Key="Icons.Highlight">M20.2585648,2.00438474 C20.6382605,2.00472706 20.9518016,2.28716326 21.0011348,2.65328337 L21.0078899,2.75506004 L21.0038407,7.25276883 C21.0009137,8.40908568 20.1270954,9.36072944 19.0029371,9.48671858 L19.0024932,11.7464847 C19.0024932,12.9373487 18.0773316,13.9121296 16.906542,13.9912939 L16.7524932,13.9964847 L16.501,13.9963847 L16.5017549,16.7881212 C16.5017549,17.6030744 16.0616895,18.349347 15.3600767,18.7462439 L15.2057929,18.8258433 L8.57108142,21.9321389 C8.10484975,22.1504232 7.57411944,21.8450614 7.50959937,21.3535767 L7.50306874,21.2528982 L7.503,13.9963847 L7.25,13.9964847 C6.05913601,13.9964847 5.08435508,13.0713231 5.00519081,11.9005335 L5,11.7464847 L5.00043957,9.4871861 C3.92882124,9.36893736 3.08392302,8.49812196 3.0058865,7.41488149 L3,7.25086975 L3,2.75438506 C3,2.3401715 3.33578644,2.00438474 3.75,2.00438474 C4.12969577,2.00438474 4.44349096,2.28653894 4.49315338,2.6526145 L4.5,2.75438506 L4.5,7.25086975 C4.5,7.63056552 4.78215388,7.94436071 5.14822944,7.99402313 L5.25,8.00086975 L18.7512697,8.00087075 C19.1315998,8.00025031 19.4461483,7.71759877 19.4967392,7.3518545 L19.5038434,7.25019537 L19.5078902,2.75371008 C19.508263,2.33949668 19.8443515,2.00401258 20.2585648,2.00438474 Z M15.001,13.9963847 L9.003,13.9963847 L9.00306874,20.0736262 L14.5697676,17.4673619 C14.8004131,17.3593763 14.9581692,17.1431606 14.9940044,16.89581 L15.0017549,16.7881212 L15.001,13.9963847 Z M17.502,9.50038474 L6.5,9.50038474 L6.5,11.7464847 C6.5,12.1261805 6.78215388,12.4399757 7.14822944,12.4896381 L7.25,12.4964847 L16.7524932,12.4964847 C17.1321889,12.4964847 17.4459841,12.2143308 17.4956465,11.8482552 L17.5024932,11.7464847 L17.502,9.50038474 Z</StreamGeometry>
   <StreamGeometry x:Key="Icons.Histories">M24 512A488 488 0 01512 24A488 488 0 011000 512A488 488 0 01512 1000A488 488 0 0124 512zm447-325v327L243 619l51 111 300-138V187H471z</StreamGeometry>
   <StreamGeometry x:Key="Icons.Home">M832 64h128v278l-128-146V64zm64 448L512 73 128 512H0L448 0h128l448 512h-128zm0 83V1024H640V704c0-35-29-64-64-64h-128a64 64 0 00-64 64v320H128V595l384-424 384 424z</StreamGeometry>
   <StreamGeometry x:Key="Icons.Hotkeys">M512 0C229 0 0 229 0 512c0 283 229 512 512 512s512-229 512-512c0-283-229-512-512-512zm0 958C266 958 66 758 66 512S266 66 512 66 958 266 958 512 758 958 512 958zM192 416h96a32 32 0 0032-32v-32a32 32 0 00-32-32H192a32 32 0 00-32 32v32a32 32 0 0032 32zM384 416h96a32 32 0 0032-32v-32a32 32 0 00-32-32h-96a32 32 0 00-32 32v32a32 32 0 0032 32zM576 416h96a32 32 0 0032-32v-32a32 32 0 00-32-32h-96a32 32 0 00-32 32v32a32 32 0 0032 32zM832 320h-64a32 32 0 00-32 32v128h-160a32 32 0 00-32 32v32a32 32 0 0032 32h256a32 32 0 0032-32v-192a32 32 0 00-32-32zM320 544v-32a32 32 0 00-32-32H192a32 32 0 00-32 32v32a32 32 0 0032 32h96a32 32 0 0032-32zM384 576h96a32 32 0 0032-32v-32a32 32 0 00-32-32h-96a32 32 0 00-32 32v32a32 32 0 0032 32zM800 640H256a32 32 0 00-32 32v32a32 32 0 0032 32h544a32 32 0 0032-32v-32a32 32 0 00-32-32z</StreamGeometry>

src/Resources/Locales/en_US.axaml

@@ -233,6 +233,7 @@
   <x:String x:Key="Text.Diff.Binary.New" xml:space="preserve">NEW</x:String>
   <x:String x:Key="Text.Diff.Binary.Old" xml:space="preserve">OLD</x:String>
   <x:String x:Key="Text.Diff.Copy" xml:space="preserve">Copy</x:String>
+  <x:String x:Key="Text.Diff.HighlightedDiffNavigation" xml:space="preserve">Highlighted Diff Navigation</x:String>
   <x:String x:Key="Text.Diff.FileModeChanged" xml:space="preserve">File Mode Changed</x:String>
   <x:String x:Key="Text.Diff.IgnoreWhitespace" xml:space="preserve">Ignore Whitespace Change</x:String>
   <x:String x:Key="Text.Diff.LFS" xml:space="preserve">LFS OBJECT CHANGE</x:String>

src/ViewModels/DiffContext.cs

@@ -51,6 +51,12 @@ public int UnifiedLines
             private set => SetProperty(ref _unifiedLines, value);
         }
 
+        public string ChangeBlockIndicator
+        {
+            get => _changeBlockIndicator;
+            private set => SetProperty(ref _changeBlockIndicator, value);
+        }
+
         public DiffContext(string repo, Models.DiffOption option, DiffContext previous = null)
         {
             _repo = repo;
@@ -73,12 +79,68 @@ public DiffContext(string repo, Models.DiffOption option, DiffContext previous =
             LoadDiffContent();
         }
 
+        public void PrevChange()
+        {
+            if (_content is Models.TextDiff textDiff)
+            {
+                if (textDiff.CurrentChangeBlockIdx > 0)
+                {
+                    textDiff.CurrentChangeBlockIdx--;
+                }
+                else if (textDiff.ChangeBlocks.Count > 0)
+                {
+                    // Force property value change and (re-)jump to first change block
+                    textDiff.CurrentChangeBlockIdx = -1;
+                    textDiff.CurrentChangeBlockIdx = 0;
+                }
+            }
+            RefreshChangeBlockIndicator();
+        }
+
+        public void NextChange()
+        {
+            if (_content is Models.TextDiff textDiff)
+            {
+                if (textDiff.CurrentChangeBlockIdx < textDiff.ChangeBlocks.Count - 1)
+                {
+                    textDiff.CurrentChangeBlockIdx++;
+                }
+                else if (textDiff.ChangeBlocks.Count > 0)
+                {
+                    // Force property value change and (re-)jump to last change block
+                    textDiff.CurrentChangeBlockIdx = -1;
+                    textDiff.CurrentChangeBlockIdx = textDiff.ChangeBlocks.Count - 1;
+                }
+                RefreshChangeBlockIndicator();
+            }
+        }
+
+        public void RefreshChangeBlockIndicator()
+        {
+            string curr = "-", tot = "-";
+            if (_content is Models.TextDiff textDiff)
+            {
+                if (textDiff.CurrentChangeBlockIdx >= 0)
+                    curr = (textDiff.CurrentChangeBlockIdx + 1).ToString();
+                tot = (textDiff.ChangeBlocks.Count).ToString();
+            }
+            ChangeBlockIndicator = curr + "/" + tot;
+        }
+
         public void ToggleFullTextDiff()
         {
             Preference.Instance.UseFullTextDiff = !Preference.Instance.UseFullTextDiff;
             LoadDiffContent();
         }
 
+        public void ToggleHighlightedDiffNavigation()
+        {
+            Preference.Instance.EnableChangeBlocks = !Preference.Instance.EnableChangeBlocks;
+            if (_content is Models.TextDiff textDiff)
+                textDiff.CurrentChangeBlockIdx = -1;
+            RefreshChangeBlockIndicator();
+        }
+
         public void IncrUnified()
         {
             UnifiedLines = _unifiedLines + 1;
@@ -91,6 +153,12 @@ public void DecrUnified()
             LoadDiffContent();
         }
 
+        public void ToggleTwoSideDiff()
+        {
+            Preference.Instance.UseSideBySideDiff = !Preference.Instance.UseSideBySideDiff;
+            RefreshChangeBlockIndicator();
+        }
+
         public void OpenExternalMergeTool()
         {
             var toolType = Preference.Instance.ExternalMergeToolType;
@@ -217,7 +285,9 @@ private void LoadDiffContent()
                     FileModeChange = latest.FileModeChange;
                     Content = rs;
                     IsTextDiff = rs is Models.TextDiff;
-                });
+
+                    RefreshChangeBlockIndicator();
+                 });
             });
         }
 
@@ -281,6 +351,7 @@ public bool IsSame(Info other)
         private string _title;
         private string _fileModeChange = string.Empty;
         private int _unifiedLines = 4;
+        private string _changeBlockIndicator = "-/-";
         private bool _isTextDiff = false;
         private bool _ignoreWhitespace = false;
         private object _content = null;

src/ViewModels/Preference.cs

@@ -206,6 +206,12 @@ public bool UseFullTextDiff
             set => SetProperty(ref _useFullTextDiff, value);
         }
 
+        public bool EnableChangeBlocks
+        {
+            get => _enableChangeBlocks;
+            set => SetProperty(ref _enableChangeBlocks, value);
+        }
+
         public Models.ChangeViewMode UnstagedChangeViewMode
         {
             get => _unstagedChangeViewMode;
@@ -614,6 +620,7 @@ private bool RemoveInvalidRepositoriesRecursive(List<RepositoryNode> collection)
         private bool _enableDiffViewWordWrap = false;
         private bool _showHiddenSymbolsInDiffView = false;
         private bool _useFullTextDiff = false;
+        private bool _enableChangeBlocks = false;
 
         private Models.ChangeViewMode _unstagedChangeViewMode = Models.ChangeViewMode.List;
         private Models.ChangeViewMode _stagedChangeViewMode = Models.ChangeViewMode.List;

src/ViewModels/TwoSideTextDiff.cs

@@ -45,10 +45,43 @@ public TwoSideTextDiff(Models.TextDiff diff, TwoSideTextDiff previous = null)
 
             FillEmptyLines();
 
+            ProcessChangeBlocks();
+
             if (previous != null && previous.File == File)
                 _syncScrollOffset = previous._syncScrollOffset;
         }
 
+        public List<Models.TextDiffChangeBlock> ChangeBlocks { get; set; } = [];
+
+        public void ProcessChangeBlocks()
+        {
+            ChangeBlocks.Clear();
+            int lineIdx = 0, blockStartIdx = 0;
+            bool isNewBlock = true;
+            foreach (var line in Old) // NOTE: Same block size in both Old and New lines.
+            {
+                lineIdx++;
+                if (line.Type == Models.TextDiffLineType.Added ||
+                    line.Type == Models.TextDiffLineType.Deleted ||
+                    line.Type == Models.TextDiffLineType.None) // Empty
+                {
+                    if (isNewBlock)
+                    {
+                        isNewBlock = false;
+                        blockStartIdx = lineIdx;
+                    }
+                }
+                else
+                {
+                    if (!isNewBlock)
+                    {
+                        ChangeBlocks.Add(new Models.TextDiffChangeBlock(blockStartIdx, lineIdx - 1));
+                        isNewBlock = true;
+                    }
+                }
+            }
+        }
+
         public void ConvertsToCombinedRange(Models.TextDiff combined, ref int startLine, ref int endLine, bool isOldSide)
         {
             endLine = Math.Min(endLine, combined.Lines.Count - 1);

src/Views/DiffView.axaml

@@ -34,6 +34,15 @@
 
           <!-- Toolbar Buttons -->
           <StackPanel Grid.Column="3" Margin="8,0,0,0" Orientation="Horizontal" VerticalAlignment="Center">
+            <ToggleButton Classes="line_path"
+              Width="28"
+              Command="{Binding ToggleHighlightedDiffNavigation}"
+              IsChecked="{Binding Source={x:Static vm:Preference.Instance}, Path=EnableChangeBlocks, Mode=OneWay}"
+              IsVisible="{Binding IsTextDiff}"
+              ToolTip.Tip="{DynamicResource Text.Diff.HighlightedDiffNavigation}">
+              <Path Width="13" Height="13" Data="{StaticResource Icons.Highlight}" Margin="0,3,0,0"/>
+            </ToggleButton>
+
             <Button Classes="icon_button"
                     Width="28"
                     Click="OnGotoPrevChange"
@@ -42,6 +51,18 @@
               <Path Width="12" Height="12" Stretch="Uniform" Margin="0,6,0,0" Data="{StaticResource Icons.Up}"/>
             </Button>
 
+            <TextBlock Classes="primary"
+                       Margin="0,0,0,0"
+                       Text="{Binding ChangeBlockIndicator}"
+                       FontSize="11">
+              <TextBlock.IsVisible>
+                <MultiBinding Converter="{x:Static BoolConverters.And}">
+                  <Binding Path="IsTextDiff"/>
+                  <Binding Source="{x:Static vm:Preference.Instance}" Path="EnableChangeBlocks" Mode="OneWay"/>
+                </MultiBinding>
+              </TextBlock.IsVisible>
+            </TextBlock>
+
             <Button Classes="icon_button"
                     Width="28"
                     Click="OnGotoNextChange"
@@ -124,7 +145,8 @@
 
             <ToggleButton Classes="line_path"
                           Width="28" Height="18"
-                          IsChecked="{Binding Source={x:Static vm:Preference.Instance}, Path=UseSideBySideDiff, Mode=TwoWay}"
+                          Command="{Binding ToggleTwoSideDiff}"
+                          IsChecked="{Binding Source={x:Static vm:Preference.Instance}, Path=UseSideBySideDiff, Mode=OneWay}"
                           IsVisible="{Binding IsTextDiff}"
                           ToolTip.Tip="{DynamicResource Text.Diff.SideBySide}">
               <Path Width="12" Height="12" Data="{StaticResource Icons.LayoutHorizontal}" Margin="0,2,0,0"/>
@@ -241,7 +263,8 @@
           <DataTemplate DataType="m:TextDiff">
             <v:TextDiffView 
               UseSideBySideDiff="{Binding Source={x:Static vm:Preference.Instance}, Path=UseSideBySideDiff, Mode=OneWay}"
-              UseFullTextDiff="{Binding Source={x:Static vm:Preference.Instance}, Path=UseFullTextDiff, Mode=OneWay}"/>
+              UseFullTextDiff="{Binding Source={x:Static vm:Preference.Instance}, Path=UseFullTextDiff, Mode=OneWay}"
+              CurrentChangeBlockIdx="{Binding CurrentChangeBlockIdx, Mode=OneWay}"/>
           </DataTemplate>
 
           <!-- Empty or only EOL changes -->