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WM_INPUTLANGCHANGEREQUEST Overview Group

The WM_INPUTLANGCHANGEREQUEST message is posted to the window with the focus when the user chooses a new input language, either with the hotkey (specified in the Keyboard control panel application) or from the indicator on the system taskbar. An application can accept the change by passing the message to the DefWindowProc function or reject the change (and prevent it from taking place) by returning immediately.

WM_INPUTLANGCHANGEREQUEST
fSysCharSet = (BOOL) wParam 

hkl = (HKL) lParam;

Parameters

wParam: The lowest bit of this parameter is set if the handle of the keyboard layout can be used with the system character set. The other bits are reserved.
hkl: Identifies the new keyboard layout.

Return Values

This message is posted, not sent, to the application, so the return value is ignored. To accept the change, the application should pass the message to DefWindowProc. To reject the change, the application should return zero without calling DefWindowProc.

Default Action

When the DefWindowProc function receives the WM_INPUTLANGCHANGEREQUEST message, it activates the new input locale and notifies the application of the change by sending the WM_INPUTLANGCHANGE message.

Remarks

The language indicator is only present on the taskbar if you have installed more than one keyboard layout and if you have enabled the indicator using the Keyboard control panel application.