How to get IHTMLDocument2 from a HWND

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Summary

This article shows how to get the IHTMLDocument2 interface from a HWND. If Microsoft Active Accessibility (MSAA) is installed, you can send the WM_HTML_GETOBJECT message to the document's window (with the window class "Internet Explorer_Server") and then pass the result from SendMessage to an MSAA function, ObjectFromLresult, to get a fully marshaled IHTMLDocument2 pointer.

More Information

You must have Active Accessibility components installed on the system for the code described in this section to work. Client developers can use the SDK to develop and update Active Accessibility aids. If you incorporate the latest version of Active Accessibility and distribute new versions of your accessibility aids, you must distribute the runtime components (RDK) for clients that have been developed for Microsoft Windows 95, Windows 98, or Windows NT 4.0 with Service Pack 4 or 5. It's not necessary to include the RDK for clients developed solely for Windows 2000, or for Windows NT 4.0 with Service Pack 6. The new components are already included in these operating systems.


See the "References" section of this article for information about Active Accessibility and where to download the Active Accessibility SDK.

#include <mshtml.h>
#include <atlbase.h>
#include <oleacc.h>

BOOL CALLBACK EnumChildProc(HWND hwnd,LPARAM lParam)
{
TCHARbuf[100];

::GetClassName( hwnd, (LPTSTR)&buf, 100 );
if ( _tcscmp( buf, _T("Internet Explorer_Server") ) == 0 )
{
*(HWND*)lParam = hwnd;
return FALSE;
}
else
return TRUE;
};

//You can store the interface pointer in a member variable
//for easier access
void CDlg::OnGetDocInterface(HWND hWnd)
{
CoInitialize( NULL );

// Explicitly load MSAA so we know if it's installed
HINSTANCE hInst = ::LoadLibrary( _T("OLEACC.DLL") );
if ( hInst != NULL )
{
if ( hWnd != NULL )
{
HWND hWndChild=NULL;
// Get 1st document window
::EnumChildWindows( hWnd, EnumChildProc, (LPARAM)&hWndChild );
if ( hWndChild )
{
CComPtr<IHTMLDocument2> spDoc;
LRESULT lRes;

UINT nMsg = ::RegisterWindowMessage( _T("WM_HTML_GETOBJECT") );
::SendMessageTimeout( hWndChild, nMsg, 0L, 0L, SMTO_ABORTIFHUNG, 1000, (DWORD*)&lRes );

LPFNOBJECTFROMLRESULT pfObjectFromLresult = (LPFNOBJECTFROMLRESULT)::GetProcAddress( hInst, _T("ObjectFromLresult") );
if ( pfObjectFromLresult != NULL )
{
HRESULT hr;
hr = (*pfObjectFromLresult)( lRes, IID_IHTMLDocument, 0, (void**)&spDoc );
if ( SUCCEEDED(hr) )
{
// Change background color to red
spDoc->put_bgColor( CComVariant("red") );
}
}
} // else document not ready
} // else Internet Explorer is not running
::FreeLibrary( hInst );
} // else Active Accessibility is not installed
CoUninitialize();
}
NOTE: Before Internet Explorer 5.5, frames were implemented by hosting a new instance of Shdocvw.dll, and each frame had a separate window associated with it. Internet Explorer 5.5 implements native frames for better performance, and all frames are rendered by the same instance of Shdocvw.dll. Since there will not be a HWND for each frame for Internet Explorer 5.5 and later, the sample code described in this section will work to get to the document of the main window only. You can still get to each frame's document by using the frames collection of the main document.

References

The SDK for developers and the RDK, which installs the Active Accessibility runtime components onto the operating system, can be downloaded from the following Microsoft Web site:

For information about the Microsoft Active Accessibility support provided by the MSHTML component of Microsoft Internet Explorer, visit the following Web site:
For more information, click the following article number to view the article in the Microsoft Knowledge Base:

176792 How to connect to a running instance of Internet Explorer

Eigenschappen

Artikel-id: 249232 - Laatst bijgewerkt: 2 aug. 2012 - Revisie: 1

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