From 04a81cd9bcf03d675b6210a631adfd0201d1c1c1 Mon Sep 17 00:00:00 2001
From: "Frank A. Krueger" <fak@praeclarum.org>
Date: Fri, 16 Jun 2017 17:33:27 -0700
Subject: [PATCH] Make Children thread safe

---
 Ooui/Node.cs         | 53 +++++++++++++++++++++++++++++---------------
 Tests/ButtonTests.cs |  2 ++
 2 files changed, 37 insertions(+), 18 deletions(-)

diff --git a/Ooui/Node.cs b/Ooui/Node.cs
index dec0e0e..cf19983 100644
--- a/Ooui/Node.cs
+++ b/Ooui/Node.cs
@@ -8,10 +8,16 @@ namespace Ooui
     {
         readonly List<Node> children = new List<Node> ();
 
-        public IEnumerable<Node> Children => children;
+        public IReadOnlyList<Node> Children {
+            get {
+                lock (children) {
+                    return new List<Node> (children).AsReadOnly ();
+                }
+            }
+        }
 
         public virtual string Text {
-            get { return String.Join ("", from c in children select c.Text); }
+            get { return String.Join ("", from c in Children select c.Text); }
             set {
                 ReplaceAll (new TextNode (value ?? ""));
             }
@@ -42,18 +48,21 @@ namespace Ooui
 
         public Node InsertBefore (Node newChild, Node referenceChild)
         {
-            if (referenceChild == null) {
-                newChild.MessageSent += HandleChildMessageSent;
-                children.Add (newChild);                
-            }
-            else {
-                var index = children.IndexOf (referenceChild);
-                if (index < 0) {
-                    throw new ArgumentException ("Reference must be a child of this element", nameof (referenceChild));
-                }                
-                newChild.MessageSent += HandleChildMessageSent;
-                children.Insert (index, newChild);
+            if (newChild == null)
+                return null;
+            lock (children) {
+                if (referenceChild == null) {
+                    children.Add (newChild);
+                }
+                else {
+                    var index = children.IndexOf (referenceChild);
+                    if (index < 0) {
+                        throw new ArgumentException ("Reference must be a child of this element", nameof (referenceChild));
+                    }
+                    children.Insert (index, newChild);
+                }
             }
+            newChild.MessageSent += HandleChildMessageSent;
             SendCall ("insertBefore", newChild, referenceChild);
             return newChild;
         }
@@ -62,8 +71,10 @@ namespace Ooui
         {
             if (child == null)
                 return null;
-            if (!children.Remove (child)) {
-                throw new ArgumentException ("Child not contained in this element", nameof(child));
+            lock (children) {
+                if (!children.Remove (child)) {
+                    throw new ArgumentException ("Child not contained in this element", nameof(child));
+                }
             }
             child.MessageSent -= HandleChildMessageSent;
             SendCall ("removeChild", child);
@@ -72,9 +83,15 @@ namespace Ooui
 
         protected void ReplaceAll (Node newNode)
         {
-            var toRemove = new List<Node> (children);
-            foreach (var c in toRemove)
-                RemoveChild (c);
+            var toRemove = new List<Node> ();
+            lock (children) {
+                toRemove.AddRange (children);
+                children.Clear ();
+            }
+            foreach (var child in toRemove) {
+                child.MessageSent -= HandleChildMessageSent;
+                SendCall ("removeChild", child);
+            }
             InsertBefore (newNode, null);
         }
 
diff --git a/Tests/ButtonTests.cs b/Tests/ButtonTests.cs
index 0361c47..45a1596 100644
--- a/Tests/ButtonTests.cs
+++ b/Tests/ButtonTests.cs
@@ -12,6 +12,7 @@ namespace Tests
         public void DefaultCtor ()
         {
             var b = new Button ();
+            Assert.AreEqual (0, b.Children.Count);
             Assert.AreEqual ("button", b.TagName);
             Assert.AreEqual ("", b.Text);
         }
@@ -20,6 +21,7 @@ namespace Tests
         public void TextCtor ()
         {
             var b = new Button ("Hello World!");
+            Assert.AreEqual (1, b.Children.Count);
             Assert.AreEqual ("Hello World!", b.Text);
         }