WM_ENDSESSION message
The WM_ENDSESSION message is sent to an application after the system processes the results of the WM_QUERYENDSESSION message. The WM_ENDSESSION message informs the application whether the session is ending.
A window receives this message through its WindowProc function.
LRESULT CALLBACK WindowProc(
HWND hwnd, // handle to window
UINT uMsg, // message identifier
WPARAM wParam, // end-session option
LPARAM lParam // logoff option
);
Parameters
-
hwnd
-
A handle to the window.
-
uMsg
-
The WM_ENDSESSION identifier.
-
wParam
-
If the session is being ended, this parameter is TRUE; the session can end any time after all applications have returned from processing this message. Otherwise, it is FALSE.
-
lParam
-
This parameter can be one or more of the following values. If this parameter is 0, the system is shutting down or restarting (it is not possible to determine which event is occurring).
Value Meaning - ENDSESSION_CLOSEAPP
- 0x1
If wParam is TRUE, the application must shut down. Any data should be saved automatically without prompting the user (for more information, see Remarks). The Restart Manager sends this message when the application is using a file that needs to be replaced, when it must service the system, or when system resources are exhausted. The application will be restarted if it has registered for restart using the RegisterApplicationRestart function. For more information, see Guidelines for Applications.
If wParam is FALSE, the application should not shut down.- ENDSESSION_CRITICAL
- 0x40000000
The application is forced to shut down. - ENDSESSION_LOGOFF
- 0x80000000
The user is logging off. For more information, see Logging Off. Note that this parameter is a bit mask. To test for this value, use a bit-wise operation; do not test for equality.
Return value
If an application processes this message, it should return zero.
Remarks
Applications that have unsaved data could save the data to a temporary location and restore it the next time the application starts. It is recommended that applications save their data and state frequently; for example, automatically save data between save operations initiated by the user to reduce the amount of data to be saved at shutdown.
The application need not call the DestroyWindow or PostQuitMessage function when the session is ending.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client |
Windows XP [desktop apps | UWP apps] |
| Minimum supported server |
Windows Server 2003 [desktop apps | UWP apps] |
| Header |
|
See also