Advanced MFC Programming

Chapter 16. Context Sensitive Help
)
{
}
DWORD lData2
switch(wType)
{
case XTYP_REGISTER:
case XTYP_UNREGISTER:
case XTYP_ADVSTART:
case XTYP_ADVDATA:
case XTYP_ADVREQ:
case XTYP_ADVSTOP:
case XTYP_XACT_COMPLETE:
case XTYP_CONNECT:
case XTYP_DISCONNECT:
case XTYP_CONNECT_CONFIRM:
{
return (HDDEDATA)NULL;
}
default:
{
return (HDDEDATA)NULL;
}
}
The most important parameter here is uType, which indicates what kind of message has been sent to
this application. There are many types of DDE messages. In the callback function, we can return NULL if
we do not want to process the message. Standard DDE messages will be explained in the following
sections.
Server
Sample 15.1\DDE\Server is a standard SDI application generated by Application Wizard. The view of
this application is based on class CEditView, so that it can be used to display current server states. The
sample is a very basic DDE server, which implements DDE registration and name service registration but
actually provides no service. In the sample, the service name is “Server”. All the DDE functions are
implemented in the frame window. In the sample, function CMainFrame::InitializeDDE() is called to
initialize DDE. This function is called after the client view is created:
void CDDESrvView::OnInitialUpdate()
{
CEditView::OnInitialUpdate();
((CMainFrame *)(AfxGetApp()->m_pMainWnd))->InitializeDDE();
}
Function CMainFrame::InitializeDDE() simply calls ::DdeInitialize(…) with appropriate
parameters, if the function returns DMLERR_NO_ERROR, it further proceeds to register the name service:
void CMainFrame::InitializeDDE()
{
UINT uDdeInit;
CString szRlt;
uDdeInit=::DdeInitialize
(
&m_dwInst,
(PFNCALLBACK)DdeCallback,
APPCMD_FILTERINITS,
0L
);
switch(uDdeInit)
{
case DMLERR_NO_ERROR:
{
Hszize();
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