Loading failed with "marshaling conversion 22 not implemented"

[blackdeng]

I'm integrating the Image3dAPI and the GE loader to a Unity project. Based on the TestViewer example, it looks like the Image3dAPI can be integrated as a managed plugin to Unity. I was able to retrieve information such as the bounding box, and frame count in my Unity C# code, but when I try to access the data using GetFrame, an exception was thrown "marshaling conversion 22 not implemented". Further stack trace attached below:

  at (wrapper managed-to-native) Image3dAPI.IImage3dSource.GetFrame(intptr,uint,Image3dAPI.Cart3dGeom,uint16[],Image3dAPI.Image3d&)
  at (wrapper cominterop) Image3dAPI.IImage3dSource.GetFrame(uint,Image3dAPI.Cart3dGeom,uint16[])
  at (wrapper cominterop-invoke) Image3dAPI.IImage3dSource.GetFrame(uint,Image3dAPI.Cart3dGeom,uint16[])

It seems the exception is because Unity C# uses Mono scripting backend which does not support SAFEARRAY in runtime. All APIs that return SAFEARRAY failed in Unity (returns null instead). Would it be possible to use a alternative type for arrays so that the library can be used in Unity?

[forderud]

I'm sorry to hear about the limitation in Mono's scripting backend. I unfortunately don't think SAFEARRAY usage will be changed anytime soon, since v1 of the specification is already in commercial usage. We could consider changing it for future releases, but I fear it will lead to a more complex API. That's because it's valuable with a proper "array" object for managing image data. SAFEARRAY are also quite flexible, and facilitate both zero-copy in-process communication, copy-based out-of-process marshalling and zero-copy out-of-processing with shared memory. The latter is important for enabling security sandboxing without compromising on performance.

Have you attempted to contact Mono and suggest implementing SAFEARRAY support?