PFNCALLBACK callback function

An application-defined callback function used with the Dynamic Data Exchange Management Library (DDEML) functions. It processes Dynamic Data Exchange (DDE) transactions. The PFNCALLBACK type defines a pointer to this callback function. DdeCallback is a placeholder for the application-defined function name.

Syntax

PFNCALLBACK Pfncallback;

HDDEDATA Pfncallback(
  UINT wType,
  UINT wFmt,
  HCONV hConv,
  HSZ hsz1,
  HSZ hsz2,
  HDDEDATA hData,
  ULONG_PTR dwData1,
  ULONG_PTR dwData2
)
{...}

Parameters

wType

wFmt

hConv

hsz1

Type: HSZ

A handle to a string. The meaning of this parameter depends on the type of the current transaction. For the meaning of this parameter, see the description of the transaction type.

hsz2

Type: HSZ

A handle to a string. The meaning of this parameter depends on the type of the current transaction. For the meaning of this parameter, see the description of the transaction type.

hData

dwData1

Type: ULONG_PTR

Transaction-specific data. For the meaning of this parameter, see the description of the transaction type.

dwData2

Type: ULONG_PTR

Transaction-specific data. For the meaning of this parameter, see the description of the transaction type.

Return Value

Type: HDDEDATA

The return value depends on the transaction class. For more information about the return values, see descriptions of the individual transaction types.

Remarks

The callback function is called asynchronously for transactions that do not involve the creation or termination of conversations. An application that does not frequently accept incoming messages will have reduced DDE performance because the Dynamic Data Exchange Management Library (DDEML) uses messages to initiate transactions.

An application must register the callback function by specifying a pointer to the function in a call to the DdeInitialize function.

Requirements

   
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header ddeml.h (include Windows.h)

See Also

Conceptual

DdeEnableCallback

DdeInitialize

Dynamic Data Exchange Management Library

Reference