Some platforms require COM to be initialized Fixes #463

- create a helper class
 - used primarily for XPS

binding/Binding/Binding.projitems

@@ -12,6 +12,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Definitions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)GRGlInterface.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Properties\SkiaSharpAssemblyInfo.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)SKAutoCoInitialize.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)SKImageInfo.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)SKColor.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)SKColorTable.cs" />

binding/Binding/SKAutoCoInitialize.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace SkiaSharp
+{
+	public class SKAutoCoInitialize : IDisposable
+	{
+		private long hResult;
+
+		public SKAutoCoInitialize()
+		{
+			if (PlatformConfiguration.IsWindows)
+				hResult = CoInitializeEx(IntPtr.Zero, COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE);
+			else
+				hResult = S_OK;
+		}
+
+		public bool Initialized => hResult >= 0 || hResult == RPC_E_CHANGED_MODE;
+
+		public void Uninitialize()
+		{
+			if (hResult >= 0)
+			{
+				if (PlatformConfiguration.IsWindows)
+					CoUninitialize();
+
+				hResult = -1;
+			}
+		}
+
+		public void Dispose() => Uninitialize();
+
+		private const long S_OK = 0x00000000L;
+		private const long RPC_E_CHANGED_MODE = 0x80010106L;
+
+		private const uint COINIT_MULTITHREADED = 0x0;
+		private const uint COINIT_APARTMENTTHREADED = 0x2;
+		private const uint COINIT_DISABLE_OLE1DDE = 0x4;
+		private const uint COINIT_SPEED_OVER_MEMORY = 0x8;
+
+		[DllImport("ole32.dll", CharSet = CharSet.Ansi, SetLastError = true, CallingConvention = CallingConvention.StdCall)]
+		private static extern long CoInitializeEx([In, Optional] IntPtr pvReserved, [In] uint dwCoInit);
+
+		[DllImport("ole32.dll", CharSet = CharSet.Ansi, SetLastError = true, CallingConvention = CallingConvention.StdCall)]
+		private static extern void CoUninitialize();
+	}
+}

tests/Tests/SKDocumentTest.cs

@@ -49,7 +49,8 @@ namespace SkiaSharp.Tests
 		{
 			var path = Path.Combine(PathToImages, Guid.NewGuid().ToString("D") + ".xps");
 
-			using (var doc = SKDocument.CreatePdf(path))
+			using (new SKAutoCoInitialize())
+			using (var doc = SKDocument.CreateXps(path))
 			{
 				if (IsWindows)
 				{
@@ -92,6 +93,7 @@ namespace SkiaSharp.Tests
 			using (var stream = new MemoryStream())
 			using (var managed = new SKManagedWStream(stream, false))
 			{
+				using (new SKAutoCoInitialize())
 				using (var doc = SKDocument.CreateXps(managed))
 				{
 					if (IsWindows)