WM_DDE_ADVISE

WM_DDE_ADVISE

A DDE client application posts the WM_DDE_ADVISE message to a DDE server application to request the server to supply an update for a data item whenever the item changes.

WM_DDE_ADVISE

wParam = (WPARAM) hwnd; // handle of posting application

lParam = (LPARAM) lPackedVal; // packed DDEADVISE and item atom

Parameters

hwnd

Value of wParam. Identifies the client window posting the message.

lPackedVal

Value of lParam. The component parameters packed into lPackedVal are extracted by calling the UnpackDDElParam function. The low-order word is hOptions. The high-order word is aItem.

Parameter	Description
hOptions	Identifies a global memory object containing a DDEADVISE structure that specifies how the data is to be sent.
aItem	Contains an atom that identifies the requested data item.

Remarks

If a client application supports more than one clipboard format for a single topic and item, it can post multiple WM_DDE_ADVISE messages for the topic and item, specifying a different clipboard format with each message. Note that a server can support multiple formats only for hot data links, not warm data links.

Posting

The client application posts the WM_DDE_ADVISE message by calling the PostMessage function, not the SendMessage function.

The client application allocates hOptions by calling the GlobalAlloc function with the GMEM_DDESHARE option. It allocates aItem by calling the GlobalAddAtom function.

The client application must create or reuse the WM_DDE_ADVISE lPackedVal parameter by calling the PackDDElParam function or the ReuseDDElParam function with hOptions supplied as the low-order word and aItem supplied as the high-order word.

If the receiving (server) application responds with a negative WM_DDE_ACK message, the posting (client) application must delete the hOptions object.

The fRelease flag is not used in WM_DDE_ADVISE messages, but their data-freeing behavior is similar to that of WM_DDE_DATA and WM_DDE_POKE messages where fRelease is TRUE.

Receiving

The server application posts the WM_DDE_ACK message to respond positively or negatively. When posting WM_DDE_ACK, the application can reuse the aItem atom or delete it and create a new one. If the WM_DDE_ACK message is positive, the application should delete the hOptions object; otherwise, the application should not delete the object.

The server must create or reuse the WM_DDE_ACK lPackedVal parameter by calling the PackDDElParam function or the ReuseDDElParam function with wStatus supplied as the low-order word and aItem supplied as the high-order word.