Speed up reassigning items.

Previously reassigning hierarchical items was expensive as the flattened list was being recalculated with each row disposal. Ignore collection changes while the rows are being disposed and recalculate the flattened rows at the end.
AvaloniaUI · Mar 8, 2024 · ffd6e29 · ffd6e29
1 parent bbfa905
commit ffd6e29
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Showing 2 changed files with 23 additions and 21 deletions.
diff --git a/src/Avalonia.Controls.TreeDataGrid/Models/TreeDataGrid/HierarchicalRows.cs b/src/Avalonia.Controls.TreeDataGrid/Models/TreeDataGrid/HierarchicalRows.cs
@@ -17,7 +17,7 @@ public class HierarchicalRows<TModel> : ReadOnlyListBase<HierarchicalRow<TModel>
         private readonly IExpanderColumn<TModel> _expanderColumn;
         private readonly List<HierarchicalRow<TModel>> _flattenedRows;
         private Comparison<TModel>? _comparison;
-        private bool _isExpandingCollapsing;
+        private bool _ignoreCollectionChanges;
 
         public HierarchicalRows(
             IExpanderRowController<TModel> controller,
@@ -90,10 +90,10 @@ static void Expand(IReadOnlyList<HierarchicalRow<TModel>> rows, Func<TModel, boo
                 }
             }
 
-            _isExpandingCollapsing = true;
+            _ignoreCollectionChanges = true;
 
             try { Expand(_roots, filter); }
-            finally { _isExpandingCollapsing = false; }
+            finally { _ignoreCollectionChanges = false; }
 
             _flattenedRows.Clear();
             InitializeRows();
@@ -147,7 +147,14 @@ public ICell RealizeCell(IColumn column, int columnIndex, int rowIndex)
 
         public void SetItems(TreeDataGridItemsSourceView<TModel> items)
         {
-            _roots.SetItems(items);
+            _ignoreCollectionChanges = true;
+
+            try {_roots.SetItems(items); }
+            finally { _ignoreCollectionChanges = false; }
+
+            _flattenedRows.Clear();
+            InitializeRows();
+            CollectionChanged?.Invoke(this, CollectionExtensions.ResetEvent);
         }
 
         public void Sort(Comparison<TModel>? comparison)
@@ -214,6 +221,9 @@ void IExpanderRowController<TModel>.OnChildCollectionChanged(
             IExpanderRow<TModel> row,
             NotifyCollectionChangedEventArgs e)
         {
+            if (_ignoreCollectionChanges)
+                return;
+
             if (row is HierarchicalRow<TModel> h)
                 OnCollectionChanged(h.ModelIndexPath, e);
             else
@@ -269,7 +279,7 @@ private int AddRowsAndDescendants(int index, HierarchicalRow<TModel> row)
 
         private void OnCollectionChanged(in IndexPath parentIndex, NotifyCollectionChangedEventArgs e)
         {
-            if (_isExpandingCollapsing)
+            if (_ignoreCollectionChanges)
                 return;
 
             void Add(int index, IEnumerable? items, bool raise)

diff --git a/tests/Avalonia.Controls.TreeDataGrid.Tests/HierarchicalTreeDataGridSourceTests.cs b/tests/Avalonia.Controls.TreeDataGrid.Tests/HierarchicalTreeDataGridSourceTests.cs
@@ -727,24 +727,20 @@ public void Can_Reassign_Items(bool sorted)
             {
                 var data = CreateData();
                 var target = CreateTarget(data, sorted);
-                var rowsAddedRaised = 0;
-                var rowsRemovedRaised = 0;
+                var raised = 0;
 
                 Assert.Equal(5, target.Rows.Count);
 
                 target.Rows.CollectionChanged += (s, e) =>
                 {
-                    if (e.Action == NotifyCollectionChangedAction.Add)
-                        rowsAddedRaised += e.NewItems!.Count;
-                    else if (e.Action == NotifyCollectionChangedAction.Remove)
-                        rowsRemovedRaised += e.OldItems!.Count;
+                    Assert.Equal(NotifyCollectionChangedAction.Reset, e.Action);
+                    ++raised;
                 };
 
                 target.Items = CreateData(10);
 
                 Assert.Equal(10, target.Rows.Count);
-                Assert.Equal(5, rowsRemovedRaised);
-                Assert.Equal(10, rowsAddedRaised);
+                Assert.Equal(1, raised);
             }
 
             [AvaloniaTheory(Timeout = 10000)]
@@ -754,25 +750,21 @@ public void Can_Reassign_Items_With_Expanded_Node(bool sorted)
             {
                 var data = CreateData();
                 var target = CreateTarget(data, sorted);
-                var rowsAddedRaised = 0;
-                var rowsRemovedRaised = 0;
+                var raised = 0;
 
                 target.Expand(0);
                 Assert.Equal(10, target.Rows.Count);
 
                 target.Rows.CollectionChanged += (s, e) =>
                 {
-                    if (e.Action == NotifyCollectionChangedAction.Add)
-                        rowsAddedRaised += e.NewItems!.Count;
-                    else if (e.Action == NotifyCollectionChangedAction.Remove)
-                        rowsRemovedRaised += e.OldItems!.Count;
+                    Assert.Equal(NotifyCollectionChangedAction.Reset, e.Action);
+                    ++raised;
                 };
 
                 target.Items = CreateData(12);
 
                 Assert.Equal(12, target.Rows.Count);
-                Assert.Equal(10, rowsRemovedRaised);
-                Assert.Equal(12, rowsAddedRaised);
+                Assert.Equal(1, raised);
             }
 
             [AvaloniaTheory(Timeout = 10000)]