Question

I have a html-page loaded in a CDialog in an MFC application, using the IE8 engine, and an instance of CDHtmlDialog. The html-page contains <input> elements, and includes jQuery. In said jQuery, I have this code:

$(function()
{$
  $('#Left').change(function()
  {
     $('[id$=left]').prop('disabled', ! $(this).is(':checked') );
  }).change();
});

Which essentially just keeps some inputs and selects (chosen by id convention) disabled or enabled, based on the checkbox with the id #Left.

The issue being: When I change the checkbox from the C++ code like so:

// Get pElements checkbox through doc->getElementsByTagName("input")
CComQIPtr<IHTMLInputElement> spInputElement(pElement);
spInputElement->put_checked(true);

then the change event does not fire (possibly to avoid infinite recursion), and the other inputs never update. Is there a way in which I can fire the change-event explicitly from my C++? I would prefer not to require all checkboxes to have specific html-code (such as an explicit onchange=”…”), as that would be impractical for maintenance.

Answer 1

So, thanks to amadeus, I got it figured out. This is the code that works, so everyone else can just copy-paste it if they need it.

void fireOnChangeEvent(IHTMLElement* pElement)
{
    // Create a new event-object
    IHTMLEventObj* eventObject;
    IDispatch* dispatch;
    pElement->get_document(&dispatch);
    CComQIPtr<IHTMLDocument4, &__uuidof(IHTMLDocument4)> doc = dispatch;
    dispatch->Release();
    VARIANT empty;
    VariantInit(&empty);
    doc->createEventObject(&empty, &eventObject);

    // fire event
    VARIANT eventref;
    VariantInit(&eventref);
    V_VT(&eventref) = VT_DISPATCH;
    V_DISPATCH(&eventref) = eventObject;

    VARIANT_BOOL cancellable;

    CComQIPtr<IHTMLElement3, &__uuidof(IHTMLElement3)> element3 = pElement;
    BSTR bstrChange = SysAllocString(L"onchange");
    element3->fireEvent(bstrChange, &eventref, &cancellable);
    SysFreeString(bstrChange);
}

Note that this will not fire any events described in JQuery, but it will get all those that are declared directly in the html as onchange="..."