CoCreate Modeling: Exchanging text via the Windows clipboard

We already discussed how Lisp code in CoCreate Modeling can communicate with other components in various ways:

• With Excel via DDE (see also the DDE FAQ)
• With external processes by running them from CoCreate Modeling
• By calling VBscript code (see also this example)

And now it's about time to explore yet another dimension of interprocess communication - using COM objects.

A customer recently asked for help - he needed code which exchanges data with other applications via the Windows clipboard. There is no officially supported API for this kind of communication in the Integration Kit. However, that's not really a problem because access of the clipboard is provided as a service by the COM object "InternetExplorer.Application" which is available on pretty much any Windows system. We can use Lisp to ask that COM object to help us with clipboard communication.

This article at the Windows Script Center website shows how to use the InternetExplorer.Application object from VBscript; all we need to do is to translate that example into equivalent Lisp code - such as the following.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Description:  Read text from and write text to the clipboard
;;               using COM objects
;;               Requires .NET API license
;; Author:       Claus Brod  
;; Language:     Lisp
;;
;; (C) Copyright 2007 Claus Brod, all rights reserved
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(in-package :clausbrod.de)

(defun get-clipboard-object()
  (let ((ie (.net:create-object "InternetExplorer.Application")))
    (.net:invoke ie "Navigate" "about:blank")
    (.net:get-property
     (.net:get-property
      (.net:get-property ie "Document")
      "Parentwindow")
     "ClipboardData")))

(defun text-to-clipboard(text)
  (.net:invoke (get-clipboard-object) "SetData" "Text" text))

(defun text-from-clipboard()
  (.net:invoke (get-clipboard-object) "GetData" "Text"))

So how does this code work?

First we need to instantiate and connect to InternetExplorer.Application; this is the first thing which (get-clipboard-object) does. "Instantiation" means that an Internet Explorer process is started in the background (unless an instance of IE is already running).

Second, we ask the InternetExplorer.Application to open a blank document. This is a prerequisite for the next step. From the document object that we created, we can ask our way through to the ClipboardData object (the full object path is Document.Parentwindow.ClipboardData). This is the job of the get-clipboard-object function.

And finally, the ClipboardData object has two member functions which are most useful to us: GetData and SetData. GetData can be used to retrieve data from the clipboard, while SetData pushes data to the Windows clipboard. Both functions expect us to specify the format of the data that we expect on the clipboard - in our case "Text".

Legal warning: You need a license to use the COM/.NET API. Please contact CoCreate support for details.

-- ClausBrod - 11 Apr 2007

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