5.12.3 ActiveX Controls

An ActiveX control is a COM object that needs a container to manage its graphical representation. Although ffi/com does not provide direct support for ActiveX controls, you can use ffi/com to drive Internet Explorer as an ActiveX container.

The following code demonstrates using Internet Explorer to instantiate the “Sysmon” ActiveX control that is included with Windows.

#lang racket
(require ffi/com
;; The control we want to run:
(define control-progid "Sysmon")
;; Start IE:
(define ie (com-create-instance "InternetExplorer.Application.1"))
;; Set up an event callback so that we know when the initial document
;; is ready:
(define ex (com-make-event-executor))
(void (thread (lambda () (let loop () ((sync ex)) (loop)))))
(define ready (make-semaphore))
(com-register-event-callback ie "DocumentComplete"
                             (lambda (doc url) (semaphore-post ready))
;; Navigate to get an initial document:
(com-invoke ie "Navigate" "about:blank")
(unless (= (com-get-property ie "READYSTATE") READYSTATE_COMPLETE)
  (semaphore-wait ready))
(define doc (com-get-property ie "Document"))
;; Install HTML to show the ActiveX control:
(com-invoke doc "write"
               (head (title "Demo"))
                (object ((class "object")
                         (CLASSID ,(format
                                    (let ([s (guid->string
                                      ;; must remove curly braces:
                                      (define len
                                        (string-length s))
                                      (substring s 1 (sub1 len)))))))))))
;; Configure the IE window and show it:
(com-set-property! ie "MenuBar" #f)
(com-set-property! ie "ToolBar" 0)
(com-set-property! ie "StatusBar" #f)
(com-set-property! ie "Visible" #t)
;; Extract the ActiveX control from the IE document:
(define ctl (com-get-property
             (com-invoke (com-invoke doc "getElementsByTagName" "object")
;; At this point, `ctl' is the ActiveX control;
;; demonstrate by getting a list of method names:
(com-methods ctl)