Is it possible to create Non-Generic Delegates in IronPython without CTypes?

[Hubbl3]

This is mostly an academic question as I know I can do this with ctypes pretty easily

Certain WIn32 APIs require that you pass in a delegate/callback function as part of the API call. For example EnumWindows requires:

BOOL EnumWindows(
  [in] WNDENUMPROC lpEnumFunc,
  [in] LPARAM      lParam
);

Where lpEnumFunc is a application defined callback. This is my understanding as to how IronPython would expect you to P/invoke th function and call it with a delegate:

import clr
clr.AddReference("System")
clr.AddReference("System.Core")  # Add this reference for LINQ support
import System
from System import IntPtr, Func, UInt64
from System.Runtime.InteropServices import DllImportAttribute, PreserveSigAttribute
import clrtype
from enum import Enum



EnumWindowsProc = Func[IntPtr, IntPtr, bool]

class NativeMethods(object, metaclass=clrtype.ClrClass):
    __metaclass__ = clrtype.ClrClass # https://github.com/IronLanguages/ironpython3/issues/836
    DllImport = clrtype.attribute(DllImportAttribute)
    PreserveSig = clrtype.attribute(PreserveSigAttribute)
    @staticmethod
    @DllImport("user32.dll", SetLastError=True)
    @PreserveSig()
    @clrtype.accepts(EnumWindowsProc, IntPtr)
    @clrtype.returns(UInt64)
    def EnumWindows(lpEnumFunc, lParam: IntPtr):raise NotImplementedError("No EnumWindow")


def outputwindow(hwnd, lParam):
    print("callback called", hwnd)
    return True

# Create an instance of the delegate using the callback function
delegate_instance = EnumWindowsProc(outputwindow)

# Call the EnumWindows function with the delegate instance as the callback
NativeMethods.EnumWindows(delegate_instance, IntPtr.Zero)
print("testing complete")

However, this throws an error because generic types cannot be marshalled and EnumWindowsProc = Func[IntPtr, IntPtr, bool] is the definition for a generic type Func. Is this possible under the current constraints of IronPython or is it a hard limitation and everything must go through Ctypes?

[slozier]

Digging through the codebase a bit it looks like you can create non-generic delegates in at least two ways:

clr.AddReference("Microsoft.Dynamic")
from Microsoft.Scripting.Generation import Snippets
EnumWindowsProc = Snippets.Shared.DefineDelegate("MyDelegate", bool, IntPtr, IntPtr)

clr.AddReference("IronPython")
from IronPython.Runtime.Operations import PythonOps
EnumWindowsProc = PythonOps.MakeNewCustomDelegate(System.Array[System.Type]([IntPtr, IntPtr, bool]))

I wonder if one of these would be a good fit for a helper in clrtype (probably the Snippets version)...

[Hubbl3]

The snippets method worked! thank you. I have been trying to figure this out for two weeks and that was the last piece