How about native?

JCL recently pointed me towards this, and we discussed its implementation a little.
http://manual.conitec.net/hWndTarget.htm

It's only available in A6 betas and the current liteC though. Hopefully it comes through to release soon (pokes JCL).

C++
Code:

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ev = engine_open(cmdline);
*ev->d3d_lockable = _VAR(1);
engine_frame();
ev->hWndTarget = hWnd; // hWnd = target window

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C# (some utility functions not included here, see my other post in higher languages for C# wrapper snippets)
Code:

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IntPtr evPtr = engine_open(cmdline, 0);
EngineVars ev = Marshal.PtrToStructure(evPtr, typeof(EngineVars));
ev.d3d_lockable.SetValue(1);
engine_frame();
ev.hWnd.SetValue(hWnd); //(pass IntPtr Handle of the window/control as hWnd)

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-Rhuarc