enhance: improve commit graph highlighting performance

This commit also changes the behaviour of `Selected Commits Only` and `Current Branch & Selected Commits`.
Now, if we select a commit which is already highlighted, the graph will not be re-generated.

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

Author: love-linger

src/Models/CommitGraph.cs

@@ -70,7 +70,7 @@ public class Dot
         public List<Link> Links { get; } = [];
         public List<Dot> Dots { get; } = [];
 
-        public static CommitGraph Generate(List<Commit> commits, bool firstParentOnlyEnabled, CommitGraphHighlighting highlighting, HashSet<string> highlightExtraCommits)
+        public static CommitGraph Generate(List<Commit> commits, bool recalculateMergeState, bool firstParentOnlyEnabled, CommitGraphHighlighting highlighting, HashSet<string> highlightExtraCommits)
         {
             const double unitWidth = 12;
             const double halfWidth = 6;
@@ -89,60 +89,29 @@ public static CommitGraph Generate(List<Commit> commits, bool firstParentOnlyEna
                 PathHelper major = null;
 
                 // Update merge state of this commit.
-                if (commit.IsMerged)
-                {
-                    merged.Remove(commit.SHA);
-                    foreach (var p in commit.Parents)
-                        merged.Add(p);
-                }
-                else if (merged.Remove(commit.SHA))
-                {
-                    commit.IsMerged = true;
-                    foreach (var p in commit.Parents)
-                        merged.Add(p);
-                }
-
-                // Calculate highlighted state
-                var isHighlighted = false;
-                if (highlighting == CommitGraphHighlighting.All)
-                {
-                    isHighlighted = true;
-                }
-                else if (highlighting == CommitGraphHighlighting.CurrentBranchOnly)
-                {
-                    isHighlighted = commit.IsMerged;
-                }
-                else if (highlighting == CommitGraphHighlighting.SelectedCommitsOnly)
-                {
-                    isHighlighted = highlightExtraCommits.Remove(commit.SHA);
-                    if (isHighlighted)
-                    {
-                        commit.IsHighlightedInGraph = true;
-                        foreach (var p in commit.Parents)
-                            highlightExtraCommits.Add(p);
-                    }
-                }
-                else
+                if (recalculateMergeState)
                 {
                     if (commit.IsMerged)
                     {
-                        isHighlighted = true;
+                        merged.Remove(commit.SHA);
+                        foreach (var p in commit.Parents)
+                            merged.Add(p);
                     }
-                    else if (highlightExtraCommits.Remove(commit.SHA))
+                    else if (merged.Remove(commit.SHA))
                     {
-                        isHighlighted = true;
+                        commit.IsMerged = true;
                         foreach (var p in commit.Parents)
-                            highlightExtraCommits.Add(p);
+                            merged.Add(p);
                     }
                 }
-                commit.IsHighlightedInGraph = isHighlighted;
 
                 // Update current y offset
                 offsetY += unitHeight;
 
                 // Find first curves that links to this commit and marks others that links to this commit ended.
                 var offsetX = 4 - halfWidth;
                 var maxOffsetOld = unsolved.Count > 0 ? unsolved[^1].LastX : offsetX + unitWidth;
+                var isHighlighted = false;
                 foreach (var l in unsolved)
                 {
                     if (l.Next.Equals(commit.SHA, StringComparison.Ordinal))
@@ -151,6 +120,7 @@ public static CommitGraph Generate(List<Commit> commits, bool firstParentOnlyEna
                         {
                             offsetX += unitWidth;
                             major = l;
+                            isHighlighted = major.IsHighlighted;
 
                             if (commit.Parents.Count > 0)
                             {
@@ -167,6 +137,9 @@ public static CommitGraph Generate(List<Commit> commits, bool firstParentOnlyEna
                         {
                             l.End(major.LastX, offsetY, halfHeight);
                             ended.Add(l);
+
+                            if (!isHighlighted && l.IsHighlighted)
+                                isHighlighted = true;
                         }
                     }
                     else
@@ -184,6 +157,42 @@ public static CommitGraph Generate(List<Commit> commits, bool firstParentOnlyEna
                 }
                 ended.Clear();
 
+                // Calculate highlighted state
+                if (!isHighlighted)
+                {
+                    if (highlighting == CommitGraphHighlighting.All)
+                    {
+                        isHighlighted = true;
+                    }
+                    else if (highlighting == CommitGraphHighlighting.CurrentBranchOnly)
+                    {
+                        isHighlighted = commit.IsMerged;
+                    }
+                    else if (highlighting == CommitGraphHighlighting.SelectedCommitsOnly)
+                    {
+                        isHighlighted = highlightExtraCommits.Remove(commit.SHA);
+                        if (isHighlighted)
+                        {
+                            foreach (var p in commit.Parents)
+                                highlightExtraCommits.Add(p);
+                        }
+                    }
+                    else
+                    {
+                        if (commit.IsMerged)
+                        {
+                            isHighlighted = true;
+                        }
+                        else if (highlightExtraCommits.Remove(commit.SHA))
+                        {
+                            isHighlighted = true;
+                            foreach (var p in commit.Parents)
+                                highlightExtraCommits.Add(p);
+                        }
+                    }
+                }
+                commit.IsHighlightedInGraph = isHighlighted;
+
                 // If no path found, create new curve for branch head
                 // Otherwise, create new curve for new merged commit
                 if (major == null)

src/ViewModels/Histories.cs

@@ -62,6 +62,7 @@ public List<Models.Commit> Commits
             get => _commits;
             set
             {
+                GenerateGraph(value, true);
                 if (SetProperty(ref _commits, value))
                     PostCommitsChanged();
             }
@@ -91,7 +92,8 @@ public List<Models.Commit> SelectedCommits
             get => _selectedCommits;
             set
             {
-                if (SetProperty(ref _selectedCommits, value))
+                var oldCount = _selectedCommits.Count;
+                if (SetProperty(ref _selectedCommits, value) && oldCount + value.Count > 0)
                     PostSelectedCommitsChanged();
             }
         }
@@ -179,21 +181,6 @@ public void NotifyCurrentBranchChanged()
             OnPropertyChanged(nameof(CurrentBranch));
         }
 
-        public void GenerateGraph(List<Models.Commit> commits)
-        {
-            var firstParentOnly = _repo.UIStates.HistoryShowFlags.HasFlag(Models.HistoryShowFlags.FirstParentOnly);
-            var highlighting = _repo.UIStates.GraphHighlighting;
-            var extraHeads = new HashSet<string>();
-
-            if (highlighting >= Models.CommitGraphHighlighting.SelectedCommitsOnly)
-            {
-                foreach (var c in _selectedCommits)
-                    extraHeads.Add(c.SHA);
-            }
-
-            Graph = Models.CommitGraph.Generate(commits, firstParentOnly, highlighting, extraHeads);
-        }
-
         public Models.BisectState UpdateBisectInfo()
         {
             var test = Path.Combine(_repo.GitDir, "BISECT_START");
@@ -481,7 +468,37 @@ private void PostSelectedCommitsChanged()
             }
 
             if (_repo.UIStates.GraphHighlighting >= Models.CommitGraphHighlighting.SelectedCommitsOnly)
-                GenerateGraph(_commits);
+            {
+                if (_selectedCommits.Count == 0)
+                {
+                    GenerateGraph(_commits);
+                    return;
+                }
+
+                foreach (var c in _selectedCommits)
+                {
+                    if (!c.IsHighlightedInGraph)
+                    {
+                        GenerateGraph(_commits);
+                        return;
+                    }
+                }
+            }
+        }
+
+        private void GenerateGraph(List<Models.Commit> commits, bool commitsChanged = false)
+        {
+            var firstParentOnly = _repo.UIStates.HistoryShowFlags.HasFlag(Models.HistoryShowFlags.FirstParentOnly);
+            var highlighting = _repo.UIStates.GraphHighlighting;
+            var extraHeads = new HashSet<string>();
+
+            if (highlighting >= Models.CommitGraphHighlighting.SelectedCommitsOnly)
+            {
+                foreach (var c in _selectedCommits)
+                    extraHeads.Add(c.SHA);
+            }
+
+            Graph = Models.CommitGraph.Generate(commits, commitsChanged, firstParentOnly, highlighting, extraHeads);
         }
 
         private Repository _repo = null;

src/ViewModels/Repository.cs

@@ -1218,7 +1218,6 @@ public void RefreshCommits()
                     if (_histories != null)
                     {
                         _histories.IsLoading = false;
-                        _histories.GenerateGraph(commits);
                         _histories.Commits = commits;
                         BisectState = _histories.UpdateBisectInfo();