ArcGIS Engine Developer Guide

VISUAL C++
DIID_IMapControlEvents2, // Interface to listen to
0x1, // Dispatch ID of MouseDown
OnMapControlMouseDown, // Method to call when event arrives
&g_ParamInfo_MapControl_OnMouseDown) // Parameter info for method call
END_SINK_MAP()
};
Listening to more than one IDispatch event interface on a COM
object
If a single COM object needs to receive events from more than one IDispatch
source, then this can cause compiler issues with ambiguous definitions of the
DispEventAdvise method. This is not normally a problem in a dialog box, as
AtlAdviseSinkMap will handle all the connections. The ambiguity can be avoided
by introducing different typedefs each time IDispEventSimpleImpl is inherited. The
following example illustrates a COM object called CListen, which is a sink for
dispatch events from a MapControl and a PageLayoutControl.
#pragma once
#include "resource.h"
// Main symbols
// This is the parameter information.
extern _ATL_FUNC_INFO g_ParamInfo_MapControl_OnMouseDown;
extern _ATL_FUNC_INFO g_ParamInfo_PageLayoutControl_OnMouseDown;
//
// Define some typedefs of the dispatch template.
//
class CListen; // Forward definition
typedef IDispEventSimpleImpl
IDispEventSimpleImpl_MapControl;
typedef IDispEventSimpleImpl
IDispEventSimpleImpl_PageLayoutControl;
////////////////////////////////////////////////////////////////////////////
// CListen
class ATL_NO_VTABLE CListen :
public CComObjectRootEx,
public CComCoClass,
public IDispEventSimpleImpl_MapControl,
public IDispEventSimpleImpl_PageLayoutControl,
public IListen
{
public:
CListen()
Chapter 4 • Developer environments • 133