internet-exploreractivexatlbhoieaddon

Calling BHO method from Javascript?

I am trying to call my BHO method from the javascript. The problem is same as stated in the the following posts:

  1. Call BHO from Javascript function
  2. http://social.msdn.microsoft.com/Forums/en-US/ieextensiondevelopment/thread/91d4076e-4795-4d9e-9b07-5b9c9eca62fb/
  3. Calling C++ function from JavaScript script running in a web browser control

Third link is another SO post talking about it, but I did not understand the need and code. Also the shared working sample keeps crashing on windows 7 with ie 8 and windows vista with ie 7.

If it helps my BHO is written in C++ using ATL.

What I have tried:

I have written a very basic BHO and tried the approach as mentioned here by Igor Tandetnik. There is no exception generated but when I open the following html file in IE then it says object undefined.

<html>
    <head>
        <script language='javascript'>
            function call_external(){
                try{
                alert(window.external.TestScript);
                //JQueryTest.HelloJquery('a');
                }catch(err){
                    alert(err.description );
                }
            }
        </script>
    </head>
    <body id='bodyid' onload="call_external();">
        <center><div><span>Hello jQuery!!</span></div></center>
    </boay>
</html>

Question:

  1. Please clarify whether is it possible to expose and call BHO method from javascript or do i have to expose it using an activex (as answered by jeffdav in [2] )? If yes then how to do it.
  2. Basically i want to extend the window.external but the way shown in the above link [2] uses var x = new ActiveXObject("MySampleATL.MyClass");; Is both the calling conventions are same or different?

Note:

  1. There is a related post on SO which gives hint that it is possible through inserting this [id(1), helpstring("method DoSomething")] HRESULT DoSomething(); in the BHO IDL file. I am not sure how it was done and couldn't find any supporting resource through google.
  2. I am aware of this post calling-into-your-bho-from-a-client-script, but haven't tried it as it is solving the problem using ActiveX.
  3. My reason to avoid ActiveX is primarily due to the security restrictions.

Edit 1

It seems there is a way to extend the window.external. Check this. Specially the section titled IDocHostUIHandler::GetExternal: Extending the DOM.Now assuming our IDispatch interface is on the same object that implements IDocHostUIHandler. Then we can do something like this:

HRESULT CBrowserHost::GetExternal(IDispatch **ppDispatch) 
{
    *ppDispatch = this;
    return S_OK;
}

The problem with this approach is that it won't append to the existing windows methods, but rather replace them. Please tell if I am wrong.

Edit 2

The BHO Class:

class ATL_NO_VTABLE CTestScript :
    public CComObjectRootEx<CComSingleThreadModel>,
    public CComCoClass<CTestScript, &CLSID_TestScript>,
    public IObjectWithSiteImpl<CTestScript>,
    public IDispatchImpl<ITestScript, &IID_ITestScript, &LIBID_TestBHOLib, /*wMajor =*/ 1, /*wMinor =*/ 0>,
    public IDispEventImpl<1, CTestScript, &DIID_DWebBrowserEvents2, &LIBID_SHDocVw, 1, 1>
{
public:
    CTestScript()
    {
    }

DECLARE_REGISTRY_RESOURCEID(IDR_TESTSCRIPT)

DECLARE_NOT_AGGREGATABLE(CTestScript)

BEGIN_COM_MAP(CTestScript)
    COM_INTERFACE_ENTRY(ITestScript)
    COM_INTERFACE_ENTRY(IDispatch)
    COM_INTERFACE_ENTRY(IObjectWithSite)
END_COM_MAP()



    DECLARE_PROTECT_FINAL_CONSTRUCT()

    HRESULT FinalConstruct()
    {
        return S_OK;
    }

    void FinalRelease()
    {
    }

public:
    BEGIN_SINK_MAP(CTestScript)
        SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_DOCUMENTCOMPLETE, OnDocumentComplete)
        //SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_NAVIGATECOMPLETE2, OnNavigationComplete)
    END_SINK_MAP()

    void STDMETHODCALLTYPE OnDocumentComplete(IDispatch *pDisp, VARIANT *pvarURL);
    //void STDMETHODCALLTYPE OnNavigationComplete(IDispatch *pDisp, VARIANT *pvarURL);

    STDMETHOD(SetSite)(IUnknown *pUnkSite);

    HRESULT STDMETHODCALLTYPE DoSomething(){
        ::MessageBox(NULL, L"Hello", L"World", MB_OK);
        return S_OK;
    }
public:

//private:
    // InstallBHOMethod();

private:
    CComPtr<IWebBrowser2>  m_spWebBrowser;
    BOOL m_fAdvised;
};

// TestScript.cpp : Implementation of CTestScript

#include "stdafx.h"
#include "TestScript.h"


// CTestScript

STDMETHODIMP CTestScript::SetSite(IUnknown* pUnkSite)
{
    if (pUnkSite != NULL)
    {
        HRESULT hr = pUnkSite->QueryInterface(IID_IWebBrowser2, (void **)&m_spWebBrowser);
        if (SUCCEEDED(hr))
        {
            hr = DispEventAdvise(m_spWebBrowser);
            if (SUCCEEDED(hr))
            {
                m_fAdvised = TRUE;              
            }
        }
    }else
    {
        if (m_fAdvised)
        {
            DispEventUnadvise(m_spWebBrowser);
            m_fAdvised = FALSE;
        }
        m_spWebBrowser.Release();
    }
    return IObjectWithSiteImpl<CTestScript>::SetSite(pUnkSite);
}

void STDMETHODCALLTYPE CTestScript::OnDocumentComplete(IDispatch *pDisp, VARIANT *pvarURL)
{
        CComPtr<IDispatch> dispDoc;
        CComPtr<IHTMLDocument2> ifDoc;
        CComPtr<IHTMLWindow2> ifWnd;
        CComPtr<IDispatchEx> dispxWnd;

        HRESULT hr = m_spWebBrowser->get_Document( &dispDoc );
        hr = dispDoc.QueryInterface( &ifDoc );      
        hr = ifDoc->get_parentWindow( &ifWnd );
        hr = ifWnd.QueryInterface( &dispxWnd );

        // now ... be careful. Do exactly as described here. Very easy to make mistakes
        CComBSTR propName( L"myBho" );
        DISPID dispid;
        hr = dispxWnd->GetDispID( propName, fdexNameEnsure, &dispid );

        CComVariant varMyBho( (IDispatch*)this );
        DISPPARAMS params;
        params.cArgs = 1;
        params.cNamedArgs = 0;
        params.rgvarg = &varMyBho;            
        params.rgdispidNamedArgs = NULL;
        hr = dispxWnd->Invoke( dispid, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_PROPERTYPUT,
            &params, NULL, NULL, NULL );

}

The Javascript:

<script language='javascript'>
            function call_external(){
                try{
                alert(window.ITestScript);
                }catch(err){
                    alert(err.description );
                }
            }
        </script>

Edit 3

After spending three days on this, I think I should take the ActiveX path. Writing a basic activex is just way to easy, written one and tested on all major IE releases. I am leaving this question as open, please see comments in Uri's answer (many thanks to him). I have tried most of his suggestions (except for 4 and 5). I will also suggest you to see the MSDN IDispatcEx sample. If you find a solution then please post, if I find a solution then I will definitely update here.

Edit 4

See my last comment in URI's post. Issue Resolved.

Solution

  • Igor Tandetnik's method is the correct approach. The problem with the post is that the sample code (at least on the few pages I spotted it) is that it wasn't complete. I had many trials and errors until I got it working. Here is a good chunk of my code that does the trick:

    Say you have a class CMyBho, and you want to expose IMyBho automation object for Java scripts

    Class definition:
    You derive from the standard CComObjectRootEx, and CComCoClass to make it 'co creatble'. You have IObjectWithSiteImpl (reuse the m_spUnkSite implemented by this base class). IDispatchImpl implements your automation object, and IDispatchEventImpl is the sink to get notifications from the browser:

    class ATL_NO_VTABLE CMyBho
    : public CComObjectRootEx<CComSingleThreadModel>
    , public CComCoClass<CMyBho, &CLSID_MyBho>
    , public IObjectWithSiteImpl<CMyBho>
    , public IDispatchImpl<IMyBho, &IID_IMyBho, &LIBID_MyBhoLib, 1, 0>
    , IDispatchEventImpl<1, CMyBho, &DIID_DWebBrowserEvents2, &LIBID_SHDocVw, 1, 1>
{
    ...

public:
    BEGIN_COM_MAP(CMyBho)
        COM_INTERFACE_ENTRY(IMyBho)
        COM_INTERFACE_ENTRY(IDispatch)
        COM_INTERFACE_ENTRY(IObjectWithSite)
    END_COM_MAP()

    ...

    BEGIN_SINK_MAP(CMyBho)
        SINK_ENTRY_EX( 1, DIID_DWebBrowserEvents2, DISPID_DOCUMENTCOMPLETE, OnDocComplete )
    END_SINK_MAP()

    ...

private:
    CComPtr<IWebBrowser2> m_ifbrz;          // pointer to the hosting browser

}

    Next, the SetSite method, where you register to get the notification. Don't forget to call the base class.

    STDMETHODIMP CMyBho::SetSite( IUnknown* unkSite )
{
    ...
    hr = IObjectWithSiteImpl::SetSite( unkSite );
    if( unkSite ) {
        ...
        // advise to browser event.
        CComPtr<IServiceProvider> ifsp;
        hr = m_spUnkSite.QueryInterface( &ifsp );
        hr = ifsp->QueryService( SID_SwebBrowserApp, IID_IWebBrowser2, &m_ifbrz );
        hr = DispEventAdvise( m_ifbrz );
    }
    else {
        // release various resources (m_ifbrz will be released automatically by its dtor)
        ...
    }
...
}

    When document load is complete, this function will be called:

    void STDMETHODCALLTYPE CMyBho::onDocComplete( IDispatch* dispBrz, VARIANT* pvarUrl )
{
    CComPtr<IDispatch> dispDoc;
    CComPtr<IHTMLDocument2> ifDoc;
    CComPtr<IHTMLWindow2> ifWnd;
    CComPtr<IDispatchEx> dispxWnd;

    hr = m_ifbrz->get_Document( &dispDoc );
    hr = dispDoc.QueryInterface( &ifDoc );      
    hr = ifDoc->get_parentWindow( &ifWnd );
    hr = ifWnd.QueryInterface( &dispxWnd );

    // now ... be careful. Do exactly as described here. Very easy to make mistakes
    CComBSTR propName( L"myBho" );
    DISPID dispid;
    hr = dispxWnd->GetDispID( propName, fdexNameEnsure, &dispid );

    CComVariant varMyBho( (IDispatch*)this );
    DISPPARAMS params;
    params.cArgs = 1;
    params.cNamedArgs = 0;
    params.rgvarg = &varMyBho;            
    params.rgdispidNamedArgs = NULL;
    hr = dispxWnd->Invoke( dispid, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_PROPERTYPUTREF,
                           &params, NULL, NULL, NULL );
}

    As for your other questions:

    Hope this helped.