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ITfKeystrokeMgr::KeyDown method (msctf.h)

  • Article

Passes a key down event to the keystroke manager.

Syntax

HRESULT KeyDown(
  [in]  WPARAM wParam,
  [in]  LPARAM lParam,
  [out] BOOL   *pfEaten
);

Parameters

[in] wParam

Specifies the virtual-key code of the key. For more information about this parameter, see the wParam parameter in WM_KEYDOWN.

[in] lParam

Specifies the repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag of the key. For more information about this parameter, see the lParam parameter in WM_KEYDOWN.

[out] pfEaten

Pointer to a BOOL that, on exit, indicates if the key event was handled. If this value receives TRUE, the key event was handled and the event should not be forwarded to the application. If this value is FALSE, the key event was not handled and the event should be forwarded to the application.

Return value

This method can return one of these values.

Value Description
S_OK
 The method was successful.
S_FALSE
 There are no key event sinks installed.
E_INVALIDARG
 One or more parameters are invalid.

Remarks

If this method is successful and pfEaten receives TRUE, the application should not process the key down event. If this method does not return S_OK or pfEaten receives FALSE, the application should process the key down event. The following is an example of how this is implemented.


if(msg.message == WM_KEYDOWN)
{
    if( pKeyboardMgr->TestKeyDown(msg.wParam, msg.lParam, &fEaten) == S_OK 
        && fEaten 
        && pKeyboardMgr->KeyDown(msg.wParam, msg.lParam, &fEaten) == S_OK 
        && fEaten)
    {
        //The key was handled by the keystroke manager or a TSF text service. Do not pass the key to the application. 
        continue;
    }
    else
    {
        //Let the application process the key. 
    }
}

If the keystroke manager does not handle the key event, it passes the key event to TSF text services by calling the TSF text service ITfKeyEventSink::OnKeyDown method.

Requirements

Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps | UWP apps]
Minimum supported server Windows 2000 Server [desktop apps | UWP apps]
Target Platform Windows
Header msctf.h
DLL Msctf.dll
Redistributable TSF 1.0 on Windows 2000 Professional

See also