When hosting the WebBrowser control in a Visual C++ application, it may be
necessary to access methods or properties of the container from script on a
Web page. This article describes how to do this by implementing the
By implementing the IDocHostUIHandler interface, you can control many of
the User Interface features of the WebBrowser control in your hosting
application. IDocHostUIHandler also allows you to extend the Dynamic HTML
(DHTML) Object Model to access methods and properties of the container from
The GetExternal() method of IDocHostUIHandler provides this functionality.
When script on a Web page calls "window.external.yourMethod," the
WebBrowser control calls your GetExternal method to retrieve a pointer to
the IDispatch of your hosting application. It is through this pointer that
the WebBrowser control is able to access your methods and properties.
Once the WebBrowser control has a pointer to the IDispatch of the
container, it then calls IDispatch::GetIDsOfNames() to get the DISPID of
the method or property called from script, yourMethod in this case.
Finally, the WebBrowser control calls IDispatch::Invoke() with the DISPID
retrieved from GetIDsOfNames().
Here are the steps you must follow to extend the DHTML Object Model to be
able to access the container's methods and properties from script:
- Implement IDocHostUIHandler.
- Implement the IDocHostUIHandler::GetExternal method. Set the IDispatch
parameter to that of your container like so:
// Assumes you inherit from IDispatch
*ppDispatch = (IDispatch*)this;
- Return the dispatch ID (DISPID) of your method or property from
GetIDsOfNames. If you added your method or property using a wizard,
this will be done for you.
- Implement the DISPID of your method or property in your implementation
of IDispatch::Invoke like so:
STDMETHODIMP CAtlBrCon::Invoke(DISPID dispidMember, REFIID riid,
LCID lcid, WORD wFlags,
EXCEPINFO* pExcepInfo, UINT* puArgErr)
// Do something here
- Call a method or property of the container from script like this:
For more information about the technologies discussed in this article,
please refer to the documentation regarding Advanced Hosting Interfaces and
IDocHostUIHandler in the following MSDN web site:
(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Scott
Roberts, Microsoft Corporation