EM_GETCHARFROMPOS message processing

[Konai]

I am trying to understand how to process the EM_GETCHARFROMPOS message to determine which character I am closest to within an edit control. Is this message being sent already to the window? or is there some command I have to invoke to get this message sent when I need it based on a mouse interaction? I've been testing with DialogBoxParam window so that may also be an issue. Any information is appreciated.

[jj2007]

You have to send the message in the moment when you want to find that char.

      lea esi, pt  ; a local POINTL structure
      invoke GetCursorPos, esi
      invoke ScreenToClient, hRichEdit, esi
      invoke SendMessage, hRichEdit, EM_CHARFROMPOS, 0, esi