Merge pull request #59 from nventive/dev/dr/PerfCollections

Improve perf by batching collection change updates

src/Calculator.Shared/CalcManager/CalculatorObservableCollection.cs

@@ -1,11 +1,41 @@
 using System;
 using System.Collections.ObjectModel;
+using System.Collections.Specialized;
 using System.Linq;
 
 namespace CalculatorApp
 {
 	public class CalculatorObservableCollection<TType> : ObservableCollection<TType>
 	{
+		private int _batchUpdateCount;
+
+		public IDisposable BatchUpdate()
+		{
+			++_batchUpdateCount;
+
+			return Uno.Disposables.Disposable.Create(Release);
+
+			void Release()
+			{
+				if (--_batchUpdateCount <= 0)
+				{
+					OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+				}
+			}
+		}
+
+
+		/// <inheritdoc />
+		protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
+		{
+			if (_batchUpdateCount > 0)
+			{
+				return;
+			}
+
+			base.OnCollectionChanged(e);
+		}
+
 		public void Append(TType item)
 		{
 			Add(item);

src/Calculator.Shared/ViewModels/UnitConverterViewModel.cs

@@ -949,6 +949,8 @@ namespace CalculatorApp.ViewModel
 		}
 
 		void BuildUnitList(CalculatorList<UCM.Unit> modelUnitList)
+		{
+			using (m_Units.BatchUpdate())
 			{
 				m_Units.Clear();
 				foreach (UCM.Unit modelUnit in modelUnitList)
@@ -964,6 +966,7 @@ namespace CalculatorApp.ViewModel
 					m_Units.Append(EMPTY_UNIT);
 				}
 			}
+		}
 
 		Unit FindUnitInList(UCM.Unit target)
 		{
@@ -1283,6 +1286,8 @@ namespace CalculatorApp.ViewModel
 		}
 
 		void InitializeView()
+		{
+			using (m_Categories.BatchUpdate())
 			{
 				CalculatorList<UCM.Category> categories = m_model.GetCategories();
 				for (uint i = 0; i < categories.Size(); i++)
@@ -1290,6 +1295,7 @@ namespace CalculatorApp.ViewModel
 					Category category = new Category(categories[i]);
 					m_Categories.Append(category);
 				}
+			}
 
 			RestoreUserPreferences();
 			CurrentCategory = new Category(m_model.GetCurrentCategory());
@@ -1585,6 +1591,7 @@ namespace CalculatorApp.ViewModel
 		void RefreshSupplementaryResults()
 		{
 			lock (m_cacheMutex)
+			using(m_SupplementaryResults.BatchUpdate())
 			{
 				m_SupplementaryResults.Clear();
 
@@ -1607,7 +1614,6 @@ namespace CalculatorApp.ViewModel
 				{
 					m_SupplementaryResults.Append(whimsicals[0]);
 				}
-
 			}
 
 			RaisePropertyChanged(SupplementaryResultsPropertyName);