Custom Event Handling in COM c++

Question

I have a c#.NET class having an Event signature which is exposed to COM using an outgoing interface like this::

[ComVisible(true)]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IHehServerEvents
    {
       string EmptyEvent(object sender, CustomEventArgs args);
    }

In PluginAPI.h>> I have

class PluginAPI: public IHehServerEvents,public FB::JSAPIAuto//implemented the COM outgoing interface
{

//declared EmptyEvent method based upon tlh file

 HRESULT __stdcall EmptyEvent(VARIANT sender,IUnknown * args, BSTR * pRetVal);
        FB_JSAPI_EVENT(CSharpEvent, 2, (FB::variant,IUnknown *));

    }
    HRESULT ClassCpluss::EmptyEvent(BSTR message, BSTR * pRetVal)
    {....}

My Event helper in Firebreath statement is

FB_JSAPI_EVENT(CSharpEvent, 2, (VARIANT,struct _EventArgs *));

I also saw THIS link. SO boost::vairant is supported right?Then how to cast VARIANT to boost::variant? Any changes expected in the above statement? How to handle the above event in c# by use of VARIANT or struct?any examples would be helpful..

taxilian · Accepted Answer · 2013-07-04 19:41:42Z

1

No, boost::variant is not supported, FB::variant is supported -- it is not the same thing at all. FB::variant is actually using boost::any internally.

What you're trying to do is mix COM and FireBreath and it's not going to have a good result. Instead, create a class that talks to your COM stuff and use that from your JSAPI object. Handle the event in your object and have it call a functor (look at boost::bind and boost::function) or maybe use signals and sockets from boost. There are lots of ways you can handle it, but the key here is that you need to first get your C++ object that knows how to talk to COM and then using that object from FireBreath will be easy. Directly using a VARIANT or arbitrary struct type with firebreath events will never work.

answered Jul 4, 2013 at 19:41

taxilian

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2 Comments

Pratik Pattanayak Over a year ago

Surely knew about boost::function and boost::bind.But can you give us a link/provide an example(of handling COM events in c++) and as to what you're talking about this statement "have it call a functor (look at boost::bind and boost::function) "

taxilian Over a year ago

I haven't done any handling of COM events in c++. To see an example of using a functor, look at the SimpleStreamsHelper class in the FireBreath codebase -- it uses a boost::function callback. To see it used, look at FBTestPlugin where it uses SimpleStreamsHelper.

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