From ceece5802bb0f2e4e2153653b7403c0c73979060 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sun, 29 Nov 2015 10:22:38 +0100
Subject: [PATCH] Correctly track removal in ControlLocator.

Fixes #323.
---
 src/Markup/Perspex.Markup/ControlLocator.cs   |  6 ++--
 src/Perspex.Controls/NameScope.cs             |  2 +-
 .../ControlLocatorTests.cs                    | 30 +++++++++++++++++++
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/Markup/Perspex.Markup/ControlLocator.cs b/src/Markup/Perspex.Markup/ControlLocator.cs
index c2c080137d..4887de8a15 100644
--- a/src/Markup/Perspex.Markup/ControlLocator.cs
+++ b/src/Markup/Perspex.Markup/ControlLocator.cs
@@ -45,10 +45,12 @@ namespace Perspex.Markup
                         .OfType<IControl>();
                     var unregistered = Observable.FromEventPattern<NameScopeEventArgs>(
                         x => nameScope.Unregistered += x,
-                        x => nameScope.Unregistered -= x);
+                        x => nameScope.Unregistered -= x)
+                        .Where(x => x.EventArgs.Name == name)
+                        .Select(_ => (IControl)null);
                     return registered
                         .StartWith(nameScope.Find<IControl>(name))
-                        .TakeUntil(unregistered);
+                        .Merge(unregistered);
                 }
                 else
                 {
diff --git a/src/Perspex.Controls/NameScope.cs b/src/Perspex.Controls/NameScope.cs
index 768e9de9dc..ab64733a4b 100644
--- a/src/Perspex.Controls/NameScope.cs
+++ b/src/Perspex.Controls/NameScope.cs
@@ -102,7 +102,7 @@ namespace Perspex.Controls
             if (_inner.TryGetValue(name, out element))
             {
                 _inner.Remove(name);
-                Registered?.Invoke(this, new NameScopeEventArgs(name, element));
+                Unregistered?.Invoke(this, new NameScopeEventArgs(name, element));
             }
         }
     }
diff --git a/tests/Perspex.Markup.UnitTests/ControlLocatorTests.cs b/tests/Perspex.Markup.UnitTests/ControlLocatorTests.cs
index 14286479c2..19dbe5200b 100644
--- a/tests/Perspex.Markup.UnitTests/ControlLocatorTests.cs
+++ b/tests/Perspex.Markup.UnitTests/ControlLocatorTests.cs
@@ -71,6 +71,36 @@ namespace Perspex.Markup.UnitTests
             Assert.Equal(0, root.NameScopeUnregisteredSubscribers);
         }
 
+        [Fact]
+        public void Track_By_Name_Should_Track_Removal_And_Readd()
+        {
+            StackPanel panel;
+            TextBlock target;
+            TextBlock relativeTo;
+
+            var root = new TestRoot
+            {
+                Child = panel = new StackPanel
+                {
+                    Children = new Controls.Controls
+                    {
+                        (target = new TextBlock { Name = "target" }),
+                        (relativeTo = new TextBlock { Name = "start" }),
+                    }
+                }
+            };
+
+            var locator = ControlLocator.Track(relativeTo, "target");
+            var result = new List<IControl>();
+            locator.Subscribe(x => result.Add(x));
+
+            var other = new TextBlock { Name = "target" };
+            panel.Children.Remove(target);
+            panel.Children.Add(other);
+
+            Assert.Equal(new[] { target, null, other }, result);
+        }
+
         [Fact]
         public void Track_By_Name_Should_Find_Control_When_Tree_Changed()
         {