DdeInitialize Function

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

Syntax

UINT DdeInitialize(          LPDWORD pidInst,
    PFNCALLBACK pfnCallback,
    DWORD afCmd,
    DWORD ulRes
);
Parameters

pidInst
[in, out] Pointer 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
[out] Pointer 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
[in] 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 one or more of the following values.

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 Value


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_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_ALLSVRXACTIONS 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 CONVCONTEXT structure (CP_WINANSI or CP_WINUNICODE).

Windows 95/98/Me: DdeInitializeW is supported by the Microsoft Layer for Unicode (MSLU). To use this, you must add certain files to your application, as outlined in Microsoft Layer for Unicode on Windows 95/98/Me Systems .