WM_DDE_ACK
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
Parameters
When
responding to WM_DDE_INITIATE:
hwnd
Value of wParam.
Identifies the server window posting the message.
aApp
Value of the
low-order word of lParam. Contains an atom that identifies the replying
application.
aTopic
Value of the
high-order word of lParam. Contains an atom that identifies the topic
for which a conversation is being established.
When
responding to WM_DDE_EXECUTE:
hwnd
Value of wParam.
Identifies the server window posting the message.
lPackedVal
Value of lParam.
The component parameters that are packed into lPackedVal are extracted
by calling the UnpackDDElParam function. The low-order word is wStatus. The
high-order word is the same hCommands that was received in the
WM_DDE_EXECUTE message.
|
Parameter |
Description |
|
wStatus |
Specifies a
DDEACK
structure containing a series of flags that indicate the status of the
response. |
|
hCommands |
Identifies
a global memory object that contains the command string. |
When
replying to all other messages:
hwnd
Value of wParam.
Identifies the client or server window posting the message.
lPackedVal
Value of lParam.
The component parameters that are packed into lPackedVal are extracted
by calling the UnpackDDElParam function. The low-order word is wStatus. The
high-order word is aItem.
|
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. |
Remarks
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.
See Also