From 0617aa23a5e7253db016ebe5849f7917ce1b68aa Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 17 Oct 2015 18:05:09 +0200
Subject: [PATCH] Support Replace and Reset in ItemsPresenter.

---
 .../Presenters/ItemsPresenter.cs              | 28 ++++++++++++--
 .../Presenters/ItemsPresenterTests.cs         | 37 +++++++++++++++++++
 2 files changed, 61 insertions(+), 4 deletions(-)

diff --git a/src/Perspex.Controls/Presenters/ItemsPresenter.cs b/src/Perspex.Controls/Presenters/ItemsPresenter.cs
index 12327bdb48..0a80376aa7 100644
--- a/src/Perspex.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Perspex.Controls/Presenters/ItemsPresenter.cs
@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Collections.Specialized;
 using Perspex.Controls.Generators;
 using Perspex.Controls.Templates;
@@ -237,18 +238,37 @@ namespace Perspex.Controls.Presenters
             if (_createdPanel)
             {
                 var generator = ItemContainerGenerator;
+                IEnumerable<IControl> containers;
 
                 // TODO: Handle Move and Replace etc.
                 switch (e.Action)
                 {
                     case NotifyCollectionChangedAction.Add:
-                        Panel.Children.AddRange(
-                            generator.Materialize(e.NewStartingIndex, e.NewItems, MemberSelector));
+                        containers = generator.Materialize(e.NewStartingIndex, e.NewItems, MemberSelector);
+                        Panel.Children.AddRange(containers);
                         break;
 
                     case NotifyCollectionChangedAction.Remove:
-                        Panel.Children.RemoveAll(
-                            generator.RemoveRange(e.OldStartingIndex, e.OldItems.Count));
+                        containers = generator.RemoveRange(e.OldStartingIndex, e.OldItems.Count);
+                        Panel.Children.RemoveAll(containers);
+                        break;
+
+                    case NotifyCollectionChangedAction.Replace:
+                        generator.Dematerialize(e.OldStartingIndex, e.OldItems.Count);
+                        containers = generator.Materialize(e.NewStartingIndex, e.NewItems, MemberSelector);
+
+                        var i = e.NewStartingIndex;
+
+                        foreach (var container in containers)
+                        {
+                            Panel.Children[i++] = container;
+                        }
+
+                        break;
+
+                    case NotifyCollectionChangedAction.Reset:
+                        Panel.Children.RemoveAll(generator.Clear());
+                        Panel.Children.AddRange(generator.Materialize(0, Items, MemberSelector));
                         break;
                 }
 
diff --git a/tests/Perspex.Controls.UnitTests/Presenters/ItemsPresenterTests.cs b/tests/Perspex.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
index a41d4e326d..c6354cc417 100644
--- a/tests/Perspex.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
+++ b/tests/Perspex.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
@@ -1,6 +1,7 @@
 // Copyright (c) The Perspex Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
+using System.Collections.ObjectModel;
 using System.Linq;
 using Perspex.Collections;
 using Perspex.Controls.Generators;
@@ -80,6 +81,42 @@ namespace Perspex.Controls.UnitTests.Presenters
 
         [Fact]
         public void Clearing_Items_Should_Remove_Containers()
+        {
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var target = new ItemsPresenter
+            {
+                Items = items,
+            };
+
+            target.ApplyTemplate();
+            items.Clear();
+
+            Assert.Empty(target.Panel.Children);
+            Assert.Empty(target.ItemContainerGenerator.Containers);
+        }
+
+        [Fact]
+        public void Replacing_Items_Should_Update_Containers()
+        {
+            var items = new ObservableCollection<string> { "foo", "bar", "baz" };
+            var target = new ItemsPresenter
+            {
+                Items = items,
+            };
+
+            target.ApplyTemplate();
+            items[1] = "baz";
+
+            var text = target.Panel.Children
+                .OfType<TextBlock>()
+                .Select(x => x.Text)
+                .ToList();
+
+            Assert.Equal(new[] { "foo", "baz", "baz" }, text);
+        }
+
+        [Fact]
+        public void Setting_Items_To_Null_Should_Remove_Containers()
         {
             var target = new ItemsPresenter
             {