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

  • Migrating away from Windows Server 2003 is an investment in your organization's future, and there has never been a better time to begin the migration process. Take the next step to transform your datacenter by upgrading your server platform with leading edge Windows Operating Systems and SanDisk flash solutions.

  • The 2014 State of DevOps Report — based on a survey of 9,200+ people in IT operations, software development and technology management roles in 110 countries — reveals: Companies with high-performing IT organizations are twice as likely to exceed their profitability, market share and productivity goals. IT performance improves with DevOps maturity, and strongly correlates with well-known DevOps practices. Job satisfaction is the No. 1 predictor of performance against organizational …

Most Popular Programming Stories

More for Developers

RSS Feeds

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