WebBrowser: How to cast the document object

[zdp]

Hi, all,

My project is based on wxPython, and I need an IE control (i.e.
WebBrowser ActiveX control). Although the wxPython implements a
wrapped version (wx.lib.iewin.IEHtmlWindow), but it doesn't meet all
my demands, because  I need to custom many behaviors of the control.
So I thought I should use it through ActiveXWrapper directly.

So I use makepy to make the typelib of "Microsoft Internet Controls"
and "Microsoft HTML Object Library". Now I can get the document object
of the WebBrowser, and I can cast it into any interface I need like
IHtmlDocument2, IHtmlDocument3...  So far, so good.

The document object also implements a COM interface
IPersistStreamInit, which has a *Load* method. Calling this method can
load any stream into the browser control. Here is the a example using
this method in visual c++:

	IPersistStreamInit* spPSI = NULL;
	CStreamOnCString stream(szHTML);
	if (m_pHtmlDoc)  {
		m_hResult = m_pHtmlDoc->QueryInterface(IID_IPersistStreamInit,
(void**)&spPSI);
		if( SUCCEEDED(m_hResult) && spPSI ) {
			m_hResult = spPSI->Load(static_cast<IStream*>(&stream));
			spPSI->Release();
		}
	}

Now I need to call this method on my document object, my code is just
like

            stream = win32com.client.CastTo(doc, "IPersistStreamInit")
            stream.Load(somestr)

But I got an error:

ValueError: The interface name 'IPersistStreamInit' does not appear in
the same
library as object '<win32com.gen_py.Microsoft HTML Object
Library.DispHTMLDocume
nt instance at 0x46359096>'

I googled and someones says only interfaces inherit from IDispatch can
be used by pythoncom. But IPersistStreamInit interface inherits from
IUnknown. But I just need to use
this interface.

However, I also noted that the class wx.lib.iewin.IEHtmlWindow has a
*LoadStream* method, I thought it's a wrapper of IPersistStreamInit's
Load method. So I trace the source code, but only found the implement
is in the c++ base class.

Could anybody tell me how to do it? Any clues is helpful.

Dapu