MSHTML: Callback on image insertion

Question

Currently I am working on embedding a HTML editor into a C++ WinAPI application using the MSHTML component.

I got everything set up (activating editing mode, changing font face, etc.), but now I have to support inserting images. MSHTML already has support for it built in, but this support is - to my knowledge - not enough.

Somehow I need a way to intercept the insertion of images into the HTML-editor, since I have to create a list of images in the UI of our application. So, whenever the user uses the default-dialog of the MSHTML-component to insert an image or updates its source (e.g. from file://xyz.jpg to file://abc.jpg), I want my code to be notified.

I already looked at the conecpt of "Edit Designers", the implementation of IHTMLEditHost, or the DWebBrowserEvents2 interface. But nothing seems to do the trick.

Perhaps someone can give me a hint?

Answer 1

Okay,

it looks like you cannot explicitly subscribe for specific changes of the document. What you can do is to create a so-called "Change Sink".

Everytime you change the document, either by user input or programmatically, you can get a notification that "something" changed in your document. This can be done by implementing the IHTMLChangeSink interface and attaching it to the IMarkupContainer2 of the IHTMLDocument2.

Example code (not complete):

class CHTMLChangeSink : public IHTMLChangeSink
{
    public:
        // Implement IUnknown: QueryInterface, AddRef, Release
        // Implement IHTMLChangeSink:
        HRESULT STDMETHODCALLTYPE Notify()
        {
            // Notify() is called everytime the document changes
            return S_OK;
        }
};

CHTMLChangeSink * pChangeSink = new CHTMLChangeSink();
IHTMLDocument2 * pDoc; // lets suppose we already have it
IMarkupContainer2 * pMarkupContainer = nullptr;
if (pDoc->QueryInterface(IID_IMarkupContainer2, reinterpret_cast<void **>(&pMarkupContainer)) == S_OK) {
    DWORD dwCookie = 1;
    // registration is done here
    pMarkupContainer->RegisterForDirtyRange(pChangeSink, &dwCookie);
}

Please be aware, that the document has to be loaded completely (register for DIID_DWebBrowserEvents2::DocumentComplete).

From now on, whenever a change in the document occurs, your Notify-method will be called and you can do further processing to find out what has changed (e.g. process the list of images in the document).

Have fun!