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ATL Event Handling Summary

In general, handling COM events is a relatively simple process. There are three main steps:

  • Implement the event interface on your object.

  • Advise the event source that your object wants to receive events.

  • Unadvise the event source when your object no longer needs to receive events.

Implementing the Interface

There are four main ways of implementing an interface using ATL.

Derive from

Suitable for Interface type

Requires you to implement all methods*

Requires a type library at run time

The interface

Vtable

Yes

No

IDispatchImpl

Dual

Yes

Yes

IDispEventImpl

Dispinterface

No

Yes

IDispEventSimpleImpl

Dispinterface

No

No

* When using ATL support classes, you are never required to implement the IUnknown or IDispatch methods manually.

Advising and Unadvising the Event Source

There are three main ways of advising and unadvising an event source using ATL.

Advise function

Unadvise function

Most suitable for use with

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Comments

AtlAdvise, CComPtrBase::Advise

AtlUnadvise

Vtable or dual interfaces

Yes

AtlAdvise is a global ATL function. CComPtrBase::Advise is used by CComPtr and CComQIPtr.

IDispEventSimpleImpl::DispEventAdvise

IDispEventSimpleImpl::DispEventUnadvise

IDispEventImpl or IDispEventSimpleImpl

No

Fewer parameters than AtlAdvise since the base class does more work.

CComCompositeControl::AdviseSinkMap(TRUE)

CComCompositeControl::AdviseSinkMap(FALSE)

ActiveX controls in Composite controls

No

CComCompositeControl::AdviseSinkMap advises all entries in the event sink map. The same function unadvises the entries. This method is called automatically by the CComCompositeControl class.

CAxDialogImpl::AdviseSinkMap(TRUE)

CAxDialogImpl::AdviseSinkMap(FALSE)

ActiveX controls in a dialog box

No

CAxDialogImpl::AdviseSinkMap advises and unadvises all ActiveX controls in the dialog resource. This is done automatically for you.

See Also

Concepts

Event Handling and ATL

Supporting IDispEventImpl