Fixed crash when pasting from clipboard (#695)

Nez.Portable/Input/Clipboard.cs

@@ -1,5 +1,5 @@
-using System.Runtime.InteropServices;
-
+using System;
+using System.Runtime.InteropServices;
 
 namespace Nez
 {
@@ -8,15 +8,71 @@ namespace Nez
 	/// </summary>
 	public class Clipboard : IClipboard
 	{
-		static IClipboard _instance;
+		private static IClipboard _instance;
+
+		[DllImport("SDL2.dll")]
+		internal static extern void SDL_free(IntPtr memblock);
+
+		// took this from c# sdl2 binding
+		public static unsafe string UTF8_ToManaged(IntPtr s, bool freePtr = false)
+		{
+			if (s == IntPtr.Zero)
+			{
+				return null;
+			}
+
+			/* We get to do strlen ourselves! */
+			byte* ptr = (byte*)s;
+			while (*ptr != 0)
+			{
+				ptr++;
+			}
+
+			/* TODO: This #ifdef is only here because the equivalent
+			 * .NET 2.0 constructor appears to be less efficient?
+			 * Here's the pretty version, maybe steal this instead:
+			 *
+			string result = new string(
+				(sbyte*) s, // Also, why sbyte???
+				0,
+				(int) (ptr - (byte*) s),
+				System.Text.Encoding.UTF8
+			);
+			 * See the CoreCLR source for more info.
+			 * -flibit
+			 */
+#if NETSTANDARD2_0
+			/* Modern C# lets you just send the byte*, nice! */
+			string result = System.Text.Encoding.UTF8.GetString(
+				(byte*)s,
+				(int)(ptr - (byte*)s)
+			);
+#else
+			/* Old C# requires an extra memcpy, bleh! */
+			int len = (int) (ptr - (byte*) s);
+			if (len == 0)
+			{
+				return string.Empty;
+			}
+			char* chars = stackalloc char[len];
+			int strLen = System.Text.Encoding.UTF8.GetChars((byte*) s, len, chars, len);
+			string result = new string(chars, 0, strLen);
+#endif
+
+			/* Some SDL functions will malloc, we have to free! */
+			if (freePtr)
+			{
+				SDL_free(s);
+			}
+			return result;
+		}
 
 		//The Monogame.Framework.dll.config maps SDL2.dll to platform specific libraries
 		[DllImport("SDL2.dll")]
 		private static extern int SDL_SetClipboardText(string text);
 
 		[DllImport("SDL2.dll")]
-		private static extern string SDL_GetClipboardText();
-
+		private static extern IntPtr SDL_GetClipboardText();
 
 		public static string GetContents()
 		{
@@ -25,28 +81,25 @@ public static string GetContents()
 			return _instance.GetContents();
 		}
 
-
 		public static void SetContents(string text)
 		{
 			if (_instance == null)
 				_instance = new Clipboard();
 			_instance.SetContents(text);
 		}
 
-
 		#region IClipboard implementation
 
 		string IClipboard.GetContents()
 		{
-			return SDL_GetClipboardText();
+			return UTF8_ToManaged(SDL_GetClipboardText(), true);
 		}
 
-
 		void IClipboard.SetContents(string text)
 		{
 			SDL_SetClipboardText(text);
 		}
 
-		#endregion
+		#endregion IClipboard implementation
 	}
 }