VS2005 – Browser Helper Object (BHO) Tutorial

// in the Header Files -> stdafx.h, the bottom part of the file should look like this:

#include "resource.h"
#include
#include
#include

#define CAtlString CString

using namespace ATL;

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//in Source Files-> BrowserHelper.cpp you need to include

#include

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Then you need to implement methods listed here. You really shouldnt have to modify these

// this should be created by the wizard
STDMETHODIMP CBrowserHelper::InterfaceSupportsErrorInfo(REFIID riid)
{
static const IID* arr[] =
{
&IID_IBrowserHelper
};

for (int i=0; i FindConnectionPoint(DIID_DWebBrowserEvents2, &spCP);

if (FAILED(hr))
{
return hr;
}

// Subscribe the event handlers to the container
hr = spCP->Advise(reinterpret_cast(this), &m_dwCookie);

return hr;
}

STDMETHODIMP CBrowserHelper::IEUnAdvise(void)
{
HRESULT hr;
CComPtr spCP;

// Receives the connection point for WebBrowser events
hr = m_CPCptr->FindConnectionPoint(DIID_DWebBrowserEvents2, &spCP);

if (FAILED(hr))
{
return hr;
}

// Unsubscribe the event handlers to the container
hr = spCP->Unadvise(m_dwCookie);
return hr;
}

STDMETHODIMP CBrowserHelper::IEQuit(void)
{
return IEUnAdvise();
}

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//then you need to implement the invoke method, as you can see i just care about the IEBeforeNaviate2() method
//so i commented the rest of the case statements out but left them in case i need them

STDMETHODIMP CBrowserHelper::Invoke(DISPID dispidMember, REFIID riid,
LCID lcid, WORD wFlags,
DISPPARAMS* pDispParams,
VARIANT* pvarResult,
EXCEPINFO* pExcepInfo, UINT* puArgErr)
{

if (!pDispParams)
{
return E_INVALIDARG;
}

switch(dispidMember)
{
case DISPID_BEFORENAVIGATE2: // Before Naigation
IEBeforeNavigate2(pDispParams);
break;

// case DISPID_COMMANDSTATECHANGE:// Command state change
// IECommandStateChange(pDispParams);
//break;

// case DISPID_DOCUMENTCOMPLETE: // Document completed
// IEDocumentComplete(pDispParams);
//break;

// case DISPID_DOWNLOADCOMPLETE: // Download completed
// IEDownloadComplete(pDispParams);
//break;

// case DISPID_NAVIGATECOMPLETE2: // Navigation completed
// IENavigateComplete2(pDispParams);
//break;

// case DISPID_NEWWINDOW2: // Open a new window
// IENewWindow2(pDispParams);
//break;

// case DISPID_PROGRESSCHANGE: // The progress status change
// IEProgressChange(pDispParams);
//break;

// case DISPID_STATUSTEXTCHANGE: // The status bar text change
// IEStatusTextChange(pDispParams);
//break;

// case DISPID_TITLECHANGE: // Title change
// IETitleChange(pDispParams);
//break;

// case DISPID_ONQUIT: // Quit
// IEQuit();
//break;
}
return S_OK;

}

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//then implement BeforeNavigate2 - you can see the relevant code between the ***** that will
//check if IE is on google and redirect them to yahoo. You can add more code here like checking registry for a key,
//launching a process, etc, etc

void CBrowserHelper::IEBeforeNavigate2(DISPPARAMS* pDispParams)
{
CComQIPtr WebBrowser2Ptr;
CAtlString url;
VARIANT_BOOL* ptrBoolCancel;
VARTYPE vt;

// Check the type of IWebBrowser2
vt = pDispParams->rgvarg[6].vt;
if(vt == 0x0009)
{
WebBrowser2Ptr = pDispParams->rgvarg[6].pdispVal;
}
else
{
// Wrong type, return.
return;
}

// Check the first parameter type is VT_BYREF|VT_BOOL or not
vt = pDispParams->rgvarg[0].vt;
if(vt == 0x400B)
{
ptrBoolCancel = pDispParams->rgvarg[0].pboolVal;
}
else
{
// Wrong type, return.
return;
}

// Check the URL parameter type
vt = pDispParams->rgvarg[5].vt;
if(vt == 0x400C)
{
USES_CONVERSION;
url = OLE2T(pDispParams->rgvarg[5].pvarVal->bstrVal);
}
else
{
// Wrong type, return.
return;
}

// *********************************************************

// check for a given URL
if(url == _T("http://www.google.com/") || url == _T("http://www.google.com"))
{

BSTR newUrl = _T("http://www.yahoo.com/");

*ptrBoolCancel = TRUE;
WebBrowser2Ptr->Navigate(newUrl,NULL,NULL,NULL,NULL);

}

// ********************************************************
}

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//you will need to wire these up in your header file, so in HEader Files->BrowserHelper.h it would look like this

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// BrowserHelper.h : Declaration of the CBrowserHelper

#pragma once
#include "resource.h" // main symbols
#include "ExDisp.h"
#include "CompanyBrowserHelper.h"
#include "_IBrowserHelperEvents_CP.h"

#if defined(_WIN32_WCE) && !defined(_CE_DCOM) && !defined(_CE_ALLOW_SINGLE_THREADED_OBJECTS_IN_MTA)
#error "Single-threaded COM objects are not properly supported on Windows CE platform, such as the Windows Mobile platforms that do not include full DCOM support. Define _CE_ALLOW_SINGLE_THREADED_OBJECTS_IN_MTA to force ATL to support creating single-thread COM object's and allow use of it's single-threaded COM object implementations. The threading model in your rgs file was set to 'Free' as that is the only threading model supported in non DCOM Windows CE platforms."
#endif

// CBrowserHelper

class ATL_NO_VTABLE CBrowserHelper :
public CComObjectRootEx,
public CComCoClass,
public ISupportErrorInfo,
public IConnectionPointContainerImpl,
public CProxy_IBrowserHelperEvents,
public IObjectWithSiteImpl,
public IDispatchImpl
{
public:
CBrowserHelper()
{
}

DECLARE_REGISTRY_RESOURCEID(IDR_BROWSERHELPER)

BEGIN_COM_MAP(CBrowserHelper)
COM_INTERFACE_ENTRY(IBrowserHelper)
COM_INTERFACE_ENTRY(IDispatch)
COM_INTERFACE_ENTRY(ISupportErrorInfo)
COM_INTERFACE_ENTRY(IConnectionPointContainer)
COM_INTERFACE_ENTRY(IObjectWithSite)
END_COM_MAP()

BEGIN_CONNECTION_POINT_MAP(CBrowserHelper)
CONNECTION_POINT_ENTRY(__uuidof(_IBrowserHelperEvents))
END_CONNECTION_POINT_MAP()

public:

// ISupportsErrorInfo
STDMETHOD(InterfaceSupportsErrorInfo)(REFIID riid);

//
// IDispatch Methods
//
STDMETHOD(Invoke)(DISPID dispidMember,REFIID riid, LCID lcid,
WORD wFlags, DISPPARAMS* pdispparams,
VARIANT* pvarResult, EXCEPINFO* pexcepinfo,
UINT* puArgErr);

//
// IOleObjectWithSite Methods
//
STDMETHOD(SetSite)(IUnknown *pUnkSite);

DECLARE_PROTECT_FINAL_CONSTRUCT()

HRESULT FinalConstruct()
{
return S_OK;
}

void FinalRelease()
{
}

public:

private:
CComQIPtr m_CPCptr;
DWORD m_dwCookie; // Connection Token - used for
// Advise and Unadvise

enum ConnectType { Advise, Unadvise }; // What to do when managing
// the connection

STDMETHOD(IEAdvise)(void);
STDMETHOD(IEUnAdvise)(void);
STDMETHOD(IEQuit)(void);

void IEBeforeNavigate2(DISPPARAMS* pDispParams);

};

OBJECT_ENTRY_AUTO(__uuidof(BrowserHelper), CBrowserHelper)

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And Finally,

To Test:

you shouldnt have to create or modify any more code, if you build it, you should get a dll

then to register with the system you need to call

regsvr32 DllName.dll

now open a browser and goto http://www.google.com and it will redirect to yahoo!

and if you look at the loaded add-ons, it should be in the list

close all your browsers

and to unregister

regsvr32 /u DllName.dll

open a browser and try google, it should work as normal

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