The WM_DDE_ACK message notifies a DDE application of the receipt and processing of a WM_DDE_POKE, WM_DDE_EXECUTE, WM_DDE_DATA, WM_DDE_ADVISE, WM_DDE_UNADVISE, or WM_DDE_INITIATE message, and in some cases, of a WM_DDE_REQUEST message.
WM_DDE_ACK
// Response to WM_DDE_INITIATE
wParam = (WPARAM) hwnd; // handle of posting application
lParam = MAKELPARAM(aApp, aTopic) // application and topic atoms
// Response to WM_DDE_EXECUTE
wParam = (WPARAM) hwnd; // handle of posting application
lParam = (LPARAM) lPackedVal; // packed status flags and data handle
// Response to all other messages
wParam = (WPARAM) hwnd; // handle of posting application
lParam = (LPARAM) lPackedVal; // packed status flags and item
Parameter | Description |
---|---|
wStatus | Specifies a DDEACK structure containing a series of flags that indicate the status of the response. |
hCommands | Handle to a global memory object that contains the command string. |
Parameter | Description |
---|---|
wStatus | Specifies a DDEACK structure containing a series of flags that indicate the status of the response. |
aItem | Contains a global atom that identifies the name of the data item for which the response is sent. |
Posting
Except in response to the WM_DDE_INITIATE message, the application posts the WM_DDE_ACK message by calling the PostMessage function, not by calling the SendMessage function. When responding to WM_DDE_INITIATE, the application sends the WM_DDE_ACK message by calling SendMessage. In this case, neither the application-name atom nor the topic-name atom should be NULL (even if the WM_DDE_INITIATE message specified NULL atoms).
When acknowledging any message with an accompanying aItem atom, the application posting WM_DDE_ACK can either reuse the aItem atom that accompanied the original message, or it can delete it and create a new one.
When acknowledging WM_DDE_EXECUTE, the application that posts WM_DDE_ACK should reuse the global memory object identified in the original WM_DDE_EXECUTE message.
All posted WM_DDE_ACK messages must create or reuse the lPackedVal parameter by calling the PackDDElParam function or the ReuseDDElParam function.
If an application has initiated the termination of a conversation by posting WM_DDE_TERMINATE and is awaiting confirmation, the waiting application should not acknowledge (positively or negatively) any subsequent messages sent by the other application. The waiting application should delete any atoms or shared memory objects received in these intervening messages. Memory objects should not be freed if the fRelease flag is set to FALSE in WM_DDE_POKE, and WM_DDE_DATA messages.
Receiving
The application that receives a WM_DDE_ACK message should delete all atoms accompanying the message. If the application receives a WM_DDE_ACK in response to a message with an accompanying hData object, and the object was sent with the fRelease flags set to FALSE, the application is responsible for deleteing the hData object.
If the application receives a negative WM_DDE_ACK message posted in reply to a WM_DDE_ADVISE message, the application should delete the global memory object posted with the original WM_DDE_ADVISE message (in hOptions). If the application receives a negative WM_DDE_ACK message posted in reply to a WM_DDE_DATA, WM_DDE_POKE, or WM_DDE_EXECUTE message, the application should delete the global memory object posted with the original WM_DDE_DATA, WM_DDE_POKE, or WM_DDE_EXECUTE message (in hCommands).
The application that receives a posted WM_DDE_ACK message must free the lPackedVal parameter by using the FreeDDElParam function.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in dde.h.
Dynamic Data Exchange Overview, Dynamic Data Exchange Messages, DDEACK, FreeDDElParam, PackDDElParam, PostMessage, ReuseDDElParam, SendMessage, UnpackDDElParam, WM_DDE_ADVISE, WM_DDE_DATA, WM_DDE_EXECUTE, WM_DDE_INITIATE, WM_DDE_POKE, WM_DDE_REQUEST, WM_DDE_TERMINATE, WM_DDE_UNADVISE