Merge pull request #2657 from cwensley/curtis/only-trigger-datacontex…

…tchanged-when-parent-is-different

Only remove the child from parent if it is different

src/Eto/Forms/Container.cs

@@ -363,23 +363,23 @@ protected void SetParent(Control child, Action assign = null, Control previousCh
 		SuspendLayout();
 		if (Handler is IThemedControlHandler)
 		{
-			if (!ReferenceEquals(previousChild, null))
+			if (previousChild is not null)
 				RemoveLogicalParent(previousChild);
 
-			if (!ReferenceEquals(child, null) && ReferenceEquals(child.LogicalParent, null))
+			if (child is not null && child.LogicalParent is null)
 				SetLogicalParent(child);
 			assign();
 			ResumeLayout();
 			return;
 		}
-		if (!ReferenceEquals(previousChild, null) && !ReferenceEquals(previousChild, child))
+		if (previousChild is not null && !ReferenceEquals(previousChild, child))
 		{
 #if DEBUG
 			if (!ReferenceEquals(previousChild.VisualParent, this))
 				throw new ArgumentException("The previous child control is not a child of this container. Ensure you only remove children that you own.");
 #endif
 
-			if (!ReferenceEquals(previousChild.VisualParent, null))
+			if (previousChild.VisualParent is not null)
 			{
 				if (previousChild.Loaded)
 				{
@@ -393,15 +393,21 @@ protected void SetParent(Control child, Action assign = null, Control previousCh
 				previousChild.InternalLogicalParent = null;
 			}
 		}
-		if (!ReferenceEquals(child, null) && !ReferenceEquals(child.VisualParent, this))
+		if (child is not null && !ReferenceEquals(child.VisualParent, this))
 		{
 			// Detach so parent can remove from controls collection if necessary.
 			// prevents UnLoad from being called more than once when containers think a control is still a child
 			// no-op if there is no parent (handled in detach)
-			child.Detach(); //.VisualParent?.Remove(child);
+			child.VisualParent?.Remove(child);
 
-			if (ReferenceEquals(child.InternalLogicalParent, null))
+			// Remove from previous parent only if it differs
+			if (child.InternalLogicalParent is not null && !ReferenceEquals(child.InternalLogicalParent, this))
+				child.InternalLogicalParent?.Remove(child);
+
+			// Set new logical parent
+			if (child.InternalLogicalParent is null)
 				SetLogicalParent(child);
+
 			child.VisualParent = this;
 			if (Loaded && !child.Loaded)
 			{

test/Eto.Test/UnitTests/Forms/Layout/TableLayoutTests.cs

@@ -271,6 +271,32 @@ public void CopyingCellsShouldReparentChildren()
 				return layout2;
 			});
 		}
+
+		[Test]
+		public void AddingChildToAnotherPanelShouldRemoveFromTableLayout()
+		{
+			Invoke(() =>
+			{
+				var child = new Label { Text = "I should be shown!" };
+
+				var layout1 = new TableLayout { ID = "layout1" };
+				layout1.Rows.Add(child);
+				Assert.AreEqual(child.Parent, layout1, "#1.1 Child's parent should now be layout1");
+				Assert.AreEqual(child.LogicalParent, layout1, "#1.2 Child's logical parent should now be layout1");
+
+				// use the child somewheres else
+				var panel = new Panel { ID = "panel" };
+				panel.Content = child;
+
+				Assert.AreEqual(1, layout1.Rows.Count, "#2.1 layout1 should still have a row");
+				CollectionAssert.DoesNotContain(layout1.Children, child, "#2.2 Child should no longer be in layout1");
+
+				Assert.AreEqual(child.Parent, panel, "#2.3 Child's parent should now be panel");
+				Assert.AreEqual(child.LogicalParent, panel, "#2.4 Child's logical parent should now be panel");
+				CollectionAssert.Contains(panel.Children, child, "#2.5 Child should be in panel");
+			});
+		}
+
 	}
 }