WM_NULL message
Performs no operation. An application sends the WM_NULL message if it wants to post a message that the recipient window will ignore.
A window receives this message through its WindowProc function.
#define WM_NULL 0x0000
-
wParam
-
This parameter is not used.
-
lParam
-
This parameter is not used.
Type: LRESULT
An application returns zero if it processes this message.
For example, if an application has installed a WH_GETMESSAGE hook and wants to prevent a message from being processed, the GetMsgProc callback function can change the message number to WM_NULL so the recipient will ignore it.
As another example, an application can check if a window is responding to messages by sending the WM_NULL message with the SendMessageTimeout function.
Requirement | Value |
---|---|
Minimum supported client |
Windows 2000 Professional [desktop apps only] |
Minimum supported server |
Windows 2000 Server [desktop apps only] |
Header |
|