Leveraging JavaScript to Invoke C++ Code in Internet Explorer

While BHO extensions allow JavaScript to call functions in a C++ BHO, I am exploring a different scenario. Imagine that instead of using a BHO, I have a C++ console application that creates an IE COM object like this:

HRESULT hr = CoCreateInstance(
            CLSID_InternetExplorer,
            NULL,
            CLSCTX_LOCAL_SERVER,
            IID_IWebBrowser2,
            (void**)&_cBrowser);

In addition to this setup, I also have a class that "owns" the IWebBrowser2 object returned by the function:

class BrowserWrapper{
        public: 
            CComPtr<IWebBrowser2> pBrowser;

            void SomeFunction(...)
    }

My question is: Is there a way to call a function like "SomeFunction" in the wrapper class from the JavaScript within the spawned IWebBrowser2 object?

javascriptc++windowscom

Answer №1

To successfully integrate the IDocHostUIHandler interface into a web browser, you need to follow these steps outlined in the official documentation:

ComPtr<IDispatch> spDocument;
hr = spWebBrowser2->get_Document(&spDocument);
if (SUCCEEDED(hr) && (spDocument != nullptr))
{
    // Retrieve default handler from MSHTML client site
    ComPtr<IOleObject> spOleObject;
    if (SUCCEEDED(spDocument.As(&spOleObject)))
    {
        ComPtr<IOleClientSite> spClientSite;
        hr = spOleObject->GetClientSite(&spClientSite);
        if (SUCCEEDED(hr) && spClientSite)
        {
            // Store pointer for default delegation 
            m_spDefaultDocHostUIHandler = spClientSite;
        }
    }

    // Set the new custom IDocHostUIHandler
    ComPtr<ICustomDoc> spCustomDoc;
    if (SUCCEEDED(spDocument.As(&spCustomDoc)))
    {
        // Note: Define spHandler as a user-defined class
        spCustomDoc->SetUIHandler(spHandler.Get());
    }
}

It's crucial to implement the GetExternal method with precision.

In Internet Explorer's JavaScript (or VBScript), you can interact with your host using this simple call:

var ext = window.external; // Invokes your host's IDocHostUIHandler.GetExternal method
ext.SomeFunction(...); // Function implemented by your object

The output from GetExternal should always be an IDispatch object that conforms to your design specifications.

Answer №2

To solve this problem, it is important to integrate the IDocHostUIHandler interface into your system. One of the key methods within this interface is GetExternal, which requires an object that adheres to the IDispatch protocol.

Within your JavaScript code, you can trigger the process by invoking window.external.something(). This action will prompt the browser to seek out your custom external implementation - namely, the IDispatch object - and then utilize its capabilities to carry out the task specified in the something function.

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