Make sure your structures are defined like this:

POINT
  long x
  long y

TVHITTESTINFO
  point pt
  ulong flags
  longptr hItem

Make sure your external function declaration is like this:

Function long HitMsg(longptr hWnd, ulong Msg, longptr wParam,
       Ref TVHITTESTINFO lParam) Library "user32.dll" Alias For "SendMessageW"

Hi, Erick - 

Here is how I would code the External Function Declaration so that it works in either 32-bit or 64-bit:

FUNCTION Longptr HitMsg ( &
   Longptr hWnd, &
   ULong   Msg, &
   Longptr wParam, &
   Longptr lParam &
   ) LIBRARY "user32.dll" ALIAS FOR "SendMessageW"

In case you are not familiar with it, the PowerBuilder Longptr datatype is a 4-byte integer in a 32-bit process and an 8-byte integer in a 64-bit process, allowing it to be used in both without having to code and use separate declarations for each bitness.

Windows handles (such as the first argument, "hWnd") also should be defined this way, as they too expand from 32-bits in a a 32-bit process into a 64-bit value in a 64-bit process.

HTH, John

64-bit app cannot call 32-bit DLL and the data type Long might need to be handled as LongLong or LongPtr.  

You cannot simply recompile a 32-bit app as 64-bit.  You need to go through code migration process and rewrite somethings. 

Please refer to the 64-bit migration guide: https://docs.appeon.com/pb2022/migrating_32bit_applications_to_64bit/index.html

Hi Erick;

   Basically, your code has issues for sure. For example:

1. HitMsg => SendMessageW
2. Handles should be LongPTR
3. il_handle => lp_handle

HTH

Regards ... Chris