SKDocument.CreateXps() returns null in a .NET Core App

Hi,

Creating an Xps Document fails when run in a dotnet core app (the returned document instance is null), while the same code works with the full .NET Framework.

using (var stream = new SKFileWStream("test.xps"))
using (var document = SKDocument.CreateXps(stream))
{
 // document = null if run from a dotnet core 2.0 app!
}

I am using the newest SkiaSharp nuget: 1.60.0

(FYI: SKDocument.CreatePdf() works fine from a dotnet core app.) As the Xps Backend is provided by Skia I would expect it to work in SkiaSharp as well.

Take care, Martin

[mattleibow]

I managed to find the issue. It was the fact that the COM was not initialized.

https://msdn.microsoft.com/en-us/library/windows/desktop/ff485844.aspx

With the full .NET Framework, COM is already initialized as it is used by the framework itself. I am not sure how I can integrate this into SkiaSharp as this must be done outside the scope of SKDocument. the native skia has a nice utility type that I think I may be able to duplicate…

Here is a workaround:

class Program
{
	static void Main(string[] args)
	{
		CoInitializeEx(IntPtr.Zero, COINIT.COINIT_APARTMENTTHREADED | COINIT.COINIT_DISABLE_OLE1DDE);

		using (var stream = new SKFileWStream("test.xps"))
		using (var document = SKDocument.CreateXps(stream))
		{
			Console.WriteLine($"document == '{document}'");

			document.BeginPage(100, 100);
			document.EndPage();
			document.Close();
		}

		Console.WriteLine("Hello World!");

		CoUninitialize();
	}

	public enum COINIT : uint
	{
		COINIT_MULTITHREADED = 0x0,
		COINIT_APARTMENTTHREADED = 0x2,
		COINIT_DISABLE_OLE1DDE = 0x4,
		COINIT_SPEED_OVER_MEMORY = 0x8,
	}

	[DllImport("ole32.dll", CharSet = CharSet.Auto, SetLastError = true, CallingConvention = CallingConvention.StdCall)]
	public static extern int CoInitializeEx([In, Optional] IntPtr pvReserved, [In]  COINIT dwCoInit);

	[DllImport("ole32.dll", CharSet = CharSet.Auto, SetLastError = true, CallingConvention = CallingConvention.StdCall)]
	public static extern void CoUninitialize();
}

[mattleibow]

The fix in v1.60.1 will be:

using (new SKAutoCoInitialize()) {
   // use XPS bits
}

NOTE: this is only needed for some .NET Core apps. The full .NET Framework already initializes COM.