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: March 19, 2015 @ 1:00 p.m. ET / 10:00 a.m. PT The 2015 Enterprise Mobile Application Survey asked 250 mobility professionals what their biggest mobile challenges are, how many employees they are equipping with mobile apps, and their methods for driving value with mobility. Join Dan Woods, Editor and CTO of CITO Research, and Alan Murray, SVP of Products at Apperian, as they break down the results of this survey and discuss how enterprises are using mobile application management and private …

  • Companies undertaking an IT project need to find the right balance between cost and functionality. It's important to start by determining whether to build a solution from scratch, buy an out-of-the-box solution, or a combination of both. In reality, most projects will require some system tailoring to meet business requirements. Decision-makers must understand how much software development is enough and craft a detailed implementation plan to ensure the project's success. This white paper examines the different …

Most Popular Programming Stories

More for Developers

RSS Feeds

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