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ITfKeystrokeMgr::TestKeyDown method (msctf.h)

  • Article

Determines if the keystroke manager will handle a key down event.

Syntax

HRESULT TestKeyDown(
  [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 indicates if the key event would be handled. If this value receives TRUE, the key event would be handled and the event should not be forwarded to the application. If this value is FALSE, the key event would not be 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

An application can determine if a key event will be handled by the keystroke manager with this method. If this method is successful and pfEaten receives TRUE, the application should call ITfKeystrokeMgr::KeyDown. If this method does not return S_OK or pfEaten receives FALSE, the application should not call ITfKeystrokeMgr::KeyDown . 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 the TSF text services by calling the text service ITfKeyEventSink::OnTestKeyDown 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