Tip: Accessing the IHTMLDocument Interface of an HTML Frame Within Internet Explorer

When developing applications that embed the IE webbrowser control as an application rendering engine or when developing browser debugging tools, the cross-domain scripting restrictions in the browser can limit the effectiveness of developing those solutions. Sometimes you need to be able to manipulate the contents of an iframe programatically from these tools and using the DOM doesn't work because of the safeguards that the browser has in place to safeguard against cross-domain scripting attacks.

Microsoft provides the following snippet for enumerating the frames within an IHTMLDocument in the following article, How to get the WebBrowser object model of an HTML frame. This is only of limited usefulness since it only demonstrates iterating through all frames and refreshing them. The following snippet shows how to obtain the IHTMLDocument interface for an iframe by its id.

HRESULT getFrameDocumentById(IHTMLDocument2* topLevelDocument,
                             LPOLESTR frameId,
                             IHTMLDocument2** frameDocument)
{
   HRESULT hresult = E_FAIL;
   CComPtr<IOleContainer> container;
   HRESULT hr = topLevelDocument->QueryInterface(IID_IOleContainer,
                                                 (void**)&container);
   if (hr == S_OK) 
   {
      CComPtr<IEnumUnknown> enumerator;
      // Get an enumerator for the frames 
      hr = container->EnumObjects(OLECONTF_EMBEDDINGS, &enumerator);
      if (hr == S_OK) 
      {
         CComPtr<IUnknown> unk;
         ULONG uFetched;
         // Enumerate and refresh all the frames
         for (UINT i = 0; S_OK == enumerator->Next(1, &unk,
              &uFetched); i++) 
         {
            CComPtr<IWebBrowser2> browser;
            // QI for IWebBrowser here to see if we have an embedded
            // browser
            hr = unk->QueryInterface(IID_IWebBrowser2,
                                     (void**)&browser);
            if (hr == S_OK) 
            { 
               CComPtr<IHTMLElement> htmlElement;
               unk->QueryInterface(IID_IHTMLElement,
                                   (void**)&htmlElement);
               CComBSTR id;
               if (SUCCEEDED(htmlElement->get_id(&id)) && id)
               {
                  CComPtr<IDispatch> disp;
                  browser->get_Document(&disp);
                  if (disp != NULL )
                  { 
                     CComPtr<IHTMLDocument2> frameDoc;
                     hr = disp->QueryInterface( IID_IHTMLDocument2,
                                               (void**)&frameDoc);
                        if (hr == S_OK)
                        {
                           if (!wcscmp(id, frameId))
                           {
                              *frameDocument = frameDoc;
                              (*frameDocument)->AddRef();
                              hresult = S_OK;
                              break;
                        }
                     }
                  }
               }
            }
         }
      }
   }
   return hresult;
}

The author maintains a blog at http://www.znsoftware.com with more programming tips, snippets, and software.



Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • An organization's ability to identify, assess and resolve technical issues is critical to business success. Developer, operations and IT teams must be able to collect and analyze data in real-time if they which to resolve issues quickly without creating additional problems. This article introduces the idea of real-time analytics and demonstrates how log data from different layers of the system and application stack can enable real-time analytics and response.

  • As the mobile enterprise marketplace expands and customer needs grow more diverse, Samsung recognizes that solution partners and developers play an essential role by continually innovating to meet their customers' needs. Samsung works to provide these developers and partners with the latest tools and resources needed to create these solutions. Read this program guide to learn how the Samsung Enterprise Alliance Program provides partners and developers with Samsung enterprise software development kits (SDKs) …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date