ArcGIS Engine Developer Guide

VISUAL C++
// Start listening to the PageLayoutControl.
ipUnk = pPageLayoutControl;
hr = IDispEventSimpleImpl_PageLayoutControl::DispEventAdvise(ipUnk);
if (SUCCEEDED(hr))
m_ipUnkPageLayoutControl = ipUnk; // Store pointer to PageLayoutControl
for Unadvise.
The implementation of CListen also contains the following code to UnAdvise
and stop listening to the controls.
// Stop listening to the MapControl.
if (m_ipUnkMapControl!=0)
IDispEventSimpleImpl_MapControl::DispEventUnadvise(m_ipUnkMapControl);
m_ipUnkMapControl = 0;
if (m_ipUnkPageLayoutControl!=0)
IDispEventSimpleImpl_PageLayoutControl::DispEventUnadvise(m_ipUnkPageLayoutControl);
m_ipUnkPageLayoutControl= 0;
Creating a COM events source
For an object to be a source of events, it will need to provide an implementation
of IConnectionPointContainer and a mechanism to track which sinks are listening to
which IConnectionPoint interfaces. ATL provides this through the
IConnectionPointContainerImpl template. In addition, ATL provides a wizard to
generate code to fire IDispatch events for all members of a given dispatch events
interface. Below are the steps to modify an ATL COM coclass to support a connection
point:
1. First ensure that your ATL coclass has been compiled at least once. This will
allow the wizard to find an initial type library.
2. In Class view, right-click the COM object and click Implement Connection
Point.
3. Either use a definition of events from the IDL in the project or click Add
Typelib to browse for another definition.
4. Check the outbound interface to be implemented in the coclass.
Chapter 4 • Developer environments • 135