WM_SETTINGCHANGE Overview  Group

The system sends the WM_SETTINGCHANGE message to all top-level windows when the SystemParametersInfo function changes a system-wide setting. The system sends this message only if the SystemParametersInfo caller specifies the SPIF_SENDCHANGE flag.

An application can send WM_SETTINGCHANGE to all top-level windows when it makes changes to system parameters. For example, you can send this message after a call to the WriteProfileString, WriteProfileSection, or SetLocaleInfo functions, or after making changes to system parameters in the registry.

The WM_SETTINGCHANGE message is the same as the older WM_WININICHANGE message.

WM_SETTINGCHANGE 

wParam = wFlag;                         // system-wide parameter flag 

lParam = (LPARAM) (LPCTSTR) pszSection; // name of changed section or registry

 

Parameters

wFlag

Value of wParam. When the system sends the message as a result of a SystemParametersInfo call, this parameter is a flag that indicates the system parameter that was changed. For a list of values, see the SystemParametersInfo function.

When an application sends the message, this parameter must be NULL.

pszMetrics

Value of lParam. Pointer to a string that indicates the area containing the system parameter that was changed. For example, this string can be the name of a registry key or the name of a section in the WIN.INI file.

This parameter is not particularly useful in determining which system parameter changed. For example, when the string is a registry name, it typically indicates only the leaf node in the registry, not the whole path. In addition, some applications send this message with lParam set to NULL. In general, when you receive this message, you should check and reload any system parameter settings that are used by your application.

Return Values

If you process this message, return zero.

Remarks

To send the WM_SETTINGCHANGE message to all top-level windows, use the SendMessage function with the hwnd parameter set to HWND_BROADCAST.

Calls to functions that change the WIN.INI file might be mapped to the registry instead. This mapping occurs when the WIN.INI file and the section being changed are specified in the registry under the following keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
        Windows NT\CurrentVersion\IniFileMapping

The change in the storage location has no effect on the behavior of this message.

See Also

SendMessage, SetLocaleInfo, SystemParametersInfo, WM_WININICHANGE, WriteProfileSection, WriteProfileString