How can I use SendMessage?

[enthus1ast]

I think it must look like this:
    
    
    # For Reference
    # COPYDATASTRUCT* {.pure.} = object
    #   dwData*: ULONG_PTR
    #   cbData*: DWORD
    #   lpData*: PVOID
    
    # 
https://docs.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-copydatastruct
    # cbData
    # Type: DWORD
    # The size, in bytes, of the data pointed to by the lpData member.
    
    import winim
    var mydata: cstring = "Hello World"
    var cds: COPYDATASTRUCT
    cds.dwData = 0
    cds.lpData = addr mydata  # addr gets a pointer to the mydata cstring
    cds.cbData = mydata.len.DWORD
    
    
    Run

since lpData is a pointer the "size" of the pointer makes no sense here (since 
it will always be 32/64 bit).