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

  • Live Event Date: May 18, 2015 @ 1:00 p.m. ET / 10:00 a.m. PT While the idea of using facial and or gesture recognitions to create a modern, intuitive game seems attractive, some developers may want to leverage Unity 3D as a way to accelerate their development. There are many different ways in which Intel and Unity Technologies have been working together to helps speed the develop of games with the Intel® RealSense™ SDK (Software Developer Kit), so come hear from a panel of experts on what we've done …

  • Are you truly leading your team or simply managing them? Organizations need leaders and your team needs someone to follow. With some ongoing development, you could become that leader. Learn the top leadership qualities that inspire others to want to follow you and the direction of your company.

Most Popular Programming Stories

More for Developers

RSS Feeds

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