DdeInitialize

DdeInitialize

The DdeInitialize function registers an application with the Dynamic Data Exchange Management Library (DDEML). An application must call this function before calling any other DDEML function.

UINT DdeInitialize(

LPDWORD pidInst,	// pointer to instance identifier
PFNCALLBACK pfnCallback,	// pointer to callback function
DWORD afCmd,	// set of command and filter flags
DWORD ulRes	// reserved
);

Parameters

pidInst

Points to the application instance identifier. At initialization, this parameter should point to 0. If the function succeeds, this parameter points to the instance identifier for the application. This value should be passed as the idInst parameter in all other DDEML functions that require it. If an application uses multiple instances of the DDEML dynamic-link library (DLL), the application should provide a different callback function for each instance.

If pidInst points to a nonzero value, reinitialization of the DDEML is implied. In this case, pidInst must point to a valid application-instance identifier.

pfnCallback

Points to the application-defined dynamic data exchange (DDE) callback function. This function processes DDE transactions sent by the system. For more information, see the DdeCallback callback function.

afCmd

Specifies a set of APPCMD_, CBF_, and MF_ flags. The APPCMD_ flags provide special instructions to DdeInitialize. The CBF_ flags specify filters that prevent specific types of transactions from reaching the callback function. The MF_ flags specify the types of DDE activity that a DDE monitoring application monitors. Using these flags enhances the performance of a DDE application by eliminating unnecessary calls to the callback function.

This parameter can be a combination of the following filter flags:

Flag	Meaning
APPCLASS_MONITOR	Makes it possible for the application to monitor DDE activity in the system. This flag is for use by DDE monitoring applications. The application specifies the types of DDE activity to monitor by combining one or more monitor flags with the APPCLASS_MONITOR flag. For details, see the following Remarks section.
APPCLASS_STANDARD	Registers the application as a standard (nonmonitoring) DDEML application.
APPCMD_CLIENTONLY	Prevents the application from becoming a server in a DDE conversation. The application can only be a client. This flag reduces consumption of resources by the DDEML. It includes the functionality of the CBF_FAIL_ALLSVRXACTIONS flag.
APPCMD_FILTERINITS	Prevents the DDEML from sending XTYP_CONNECT and XTYP_WILDCONNECT transactions to the application until the application has created its string handles and registered its service names or has turned off filtering by a subsequent call to the DdeNameService or DdeInitialize function. This flag is always in effect when an application calls DdeInitialize for the first time, regardless of whether the application specifies the flag. On subsequent calls to DdeInitialize, not specifying this flag turns off the application's service-name filters, but specifying it turns on the application's service name filters.
CBF_FAIL_ALLSVRXACTIONS	Prevents the callback function from receiving server transactions. The system returns DDE_FNOTPROCESSED to each client that sends a transaction to this application. This flag is equivalent to combining all CBF_FAIL_ flags.
CBF_FAIL_ADVISES	Prevents the callback function from receiving XTYP_ADVSTART and XTYP_ADVSTOP transactions. The system returns DDE_FNOTPROCESSED to each client that sends an XTYP_ADVSTART or XTYP_ADVSTOP transaction to the server.
CBF_FAIL_CONNECTIONS	Prevents the callback function from receiving XTYP_CONNECT and XTYP_WILDCONNECT transactions.
CBF_FAIL_EXECUTES	Prevents the callback function from receiving XTYP_EXECUTE transactions. The system returns DDE_FNOTPROCESSED to a client that sends an XTYP_EXECUTE transaction to the server.
CBF_FAIL_POKES	Prevents the callback function from receiving XTYP_POKE transactions. The system returns DDE_FNOTPROCESSED to a client that sends an XTYP_POKE transaction to the server.
CBF_FAIL_REQUESTS	Prevents the callback function from receiving XTYP_REQUEST transactions. The system returns DDE_FNOTPROCESSED to a client that sends an XTYP_REQUEST transaction to the server.
CBF_FAIL_SELFCONNECTIONS	Prevents the callback function from receiving XTYP_CONNECT transactions from the application's own instance. This flag prevents an application from establishing a DDE conversation with its own instance. An application should use this flag if it needs to communicate with other instances of itself but not with itself.
CBF_SKIP_ALLNOTIFICATIONS	Prevents the callback function from receiving any notifications. This flag is equivalent to combining all CBF_SKIP_ flags.
CBF_SKIP_CONNECT_CONFIRMS	Prevents the callback function from receiving XTYP_CONNECT_CONFIRM notifications.
CBF_SKIP_DISCONNECTS	Prevents the callback function from receiving XTYP_DISCONNECT notifications.
CBF_SKIP_REGISTRATIONS	Prevents the callback function from receiving XTYP_REGISTER notifications.
CBF_SKIP_UNREGISTRATIONS	Prevents the callback function from receiving XTYP_UNREGISTER notifications.
MF_CALLBACKS	Notifies the callback function whenever a transaction is sent to any DDE callback function in the system.
MF_CONV	Notifies the callback function whenever a conversation is established or terminated.
MF_ERRORS	Notifies the callback function whenever a DDE error occurs.
MF_HSZ_INFO	Notifies the callback function whenever a DDE application creates, frees, or increments the usage count of a string handle or whenever a string handle is freed as a result of a call to the DdeUninitialize function.
MF_LINKS	Notifies the callback function whenever an advise loop is started or ended.
MF_POSTMSGS	Notifies the callback function whenever the system or an application posts a DDE message.
MF_SENDMSGS	Notifies the callback function whenever the system or an application sends a DDE message.

ulRes

Reserved; must be set to zero.

Return Values

If the function succeeds, the return value is DMLERR_NO_ERROR.

If the function fails, the return value is one of the following values:

DMLERR_DLL_USAGE
DMLERR_INVALIDPARAMETER
DMLERR_SYS_ERROR

Remarks

An application that uses multiple instances of the DDEML must not pass DDEML objects between instances.

A DDE monitoring application should not attempt to perform DDE operations (establish conversations, issue transactions, and so on) within the context of the same application instance.

A synchronous transaction fails with a DMLERR_REENTRANCY error if any instance of the same task has a synchronous transaction already in progress.

The CBF_FAIL_ALLSVRACTIONS flag causes the DDEML to filter all server transactions and can be changed by a subsequent call to DdeInitialize. The APPCMD_CLIENTONLY flag prevents the DDEML from creating key resources for the server and cannot be changed by a subsequent call to DdeInitialize.

There is an ANSI version and a Unicode version of DdeInitialize. The version called determines the type of the window procedures used to control DDE conversations (ANSI or Unicode), and the default value for the iCodePage member of the CONVCONTXT structure (CP_WINANSI or CP_WINUNICODE).