Copy the nodes of a SvgElement when creating a deep copy.

Added a test with a SvgText element where the whole text element was not written to XML of a deep copy of the SvgDocument.

Source/SvgContentNode.cs

-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-
-namespace Svg
+namespace Svg
 {
     public class SvgContentNode : ISvgNode
     {
         public string Content { get; set; }
+
+        /// <summary>
+        /// Create a deep copy of this <see cref="ISvgNode"/>.
+        /// </summary>
+        /// <returns>A deep copy of this <see cref="ISvgNode"/></returns>
+        public ISvgNode DeepCopy()
+        {
+            // Since strings are immutable in C#, we can just use the same reference here.
+            return new SvgContentNode { Content = this.Content };
+        }
     }
 }

Source/SvgElement.cs

@@ -833,6 +833,11 @@ namespace Svg
 
     	public abstract SvgElement DeepCopy();
 
+        ISvgNode ISvgNode.DeepCopy()
+        {
+            return DeepCopy();
+        }
+
 		public virtual SvgElement DeepCopy<T>() where T : SvgElement, new()
 		{
 			var newObj = new T();
@@ -887,7 +892,14 @@ namespace Svg
 				}
 			}
 
-			return newObj;
+            if (this._nodes.Count > 0)
+            {
+                foreach (var node in this._nodes)
+                {
+                    newObj.Nodes.Add(node.DeepCopy());
+                }
+            }
+            return newObj;
         }
 
 		/// <summary>
@@ -1197,6 +1209,12 @@ namespace Svg
     public interface ISvgNode
     {
         string Content { get; }
+        
+        /// <summary>
+        /// Create a deep copy of this <see cref="ISvgNode"/>.
+        /// </summary>
+        /// <returns>A deep copy of this <see cref="ISvgNode"/></returns>
+        ISvgNode DeepCopy();
     }
 
     /// <summary>This interface mostly indicates that a node is not to be drawn when rendering the SVG.</summary>

Tests/Svg.UnitTests/Resources/Issue_TextElement/Text.svg

+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg xmlns="http://www.w3.org/2000/svg" version="1.1" x="0px" y="0px" viewBox="0 0 34.06945 33.11168" enable-background="new 0 0 34.06945 33.11168" xml:space="preserve" id="svg2">
+    <defs id="defs30"/>
+    <text y="21.539351" x="5.6560216" style="font-size:18.9988308px;font-family:NotoSans" id="text13" font-size="18.99883px">IP</text>
+</svg>

Tests/Svg.UnitTests/Svg.UnitTests.csproj

@@ -63,6 +63,7 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="SmallEmbeddingImageTest.cs" />
     <Compile Include="SvgTestHelper.cs" />
+    <Compile Include="SvgTextElementDeepCopyTest.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\Source\Svg.csproj">
@@ -89,6 +90,9 @@
   <ItemGroup>
     <EmbeddedResource Include="Resources\hotfix-image-data-uri\Speedometer.svg" />
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Resources\Issue_TextElement\Text.svg" />
+  </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.

Tests/Svg.UnitTests/SvgTextElementDeepCopyTest.cs

+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System.IO;
+using System.Linq;
+using System.Xml;
+
+namespace Svg.UnitTests
+{
+    /// <summary>
+    /// Tests that the deep copy of a <see cref="SvgText"/> is done correctly where the
+    /// text element has contains only text and now other elements like <see cref="SvgTextSpan"/>.
+    /// </summary>
+    /// <seealso cref="Svg.UnitTests.SvgTestHelper" />
+    [TestClass]
+    public class SvgTextElementDeepCopyTest : SvgTestHelper
+    {
+        private const string PureTextElementSvg = "Issue_TextElement.Text.svg";
+        
+        [TestMethod]
+        public void TestSvgTextElementDeepCopy()
+        {
+            var svgDocument = OpenSvg(GetResourceXmlDoc(GetFullResourceString(PureTextElementSvg)));
+            CheckDocument(svgDocument);
+
+            var deepCopy = (SvgDocument)svgDocument.DeepCopy<SvgDocument>();
+            CheckDocument(deepCopy);
+        }
+
+        /// <summary>
+        /// Checks the document if it contains the correct information when exported to XML.
+        /// </summary>
+        /// <param name="svgDocument">The SVG document to check.</param>
+        private static void CheckDocument(SvgDocument svgDocument)
+        {
+            Assert.AreEqual(2, svgDocument.Children.Count);
+            Assert.IsInstanceOfType(svgDocument.Children[0], typeof(SvgDefinitionList));
+            Assert.IsInstanceOfType(svgDocument.Children[1], typeof(SvgText));
+
+            var textElement = (SvgText)svgDocument.Children[1];
+            Assert.AreEqual("IP", textElement.Content);
+
+            var memoryStream = new MemoryStream();
+            svgDocument.Write(memoryStream);
+
+            memoryStream.Seek(0, SeekOrigin.Begin);
+
+            var xmlDocument = new XmlDocument();
+            xmlDocument.Load(memoryStream);
+
+            Assert.AreEqual(2, xmlDocument.ChildNodes.Count);
+            var svgNode = xmlDocument.ChildNodes[1];
+
+            // Filter all significant whitespaces.
+            var svgChildren = svgNode.ChildNodes
+                .OfType<XmlNode>()
+                .Where(item => item.GetType() != typeof(XmlSignificantWhitespace))
+                .OfType<XmlNode>()
+                .ToArray();
+
+            Assert.AreEqual(2, svgChildren.Length);
+            var textNode = svgChildren[1];
+
+            Assert.AreEqual("text", textNode.Name);
+            Assert.AreEqual("IP", textNode.InnerText);
+        }
+    }
+}
\ No newline at end of file