VC++ keybd-event

keybd_event Function

The keybd_event function synthesizes a keystroke. The system can use such a synthesized keystroke to generate a WM_KEYUP or WM_KEYDOWN message. The keyboard driver's interrupt handler calls the keybd_event function.

Windows NT/2000/XP/Vista:This function has been superseded. Use SendInput instead.

Syntax

VOID keybd_event(      
    BYTE bVk,    BYTE bScan,    DWORD dwFlags,    PTR dwExtraInfo);

Parameters

bVk

[in] Specifies a virtual-key code. The code must be a value in the range 1 to 254. For a complete list, see Virtual Key Codes.

bScan

Specifies a hardware scan code for the key.

dwFlags

[in] Specifies various aspects of function operation. This parameter can be one or more of the following values.

KEYEVENTF_EXTENDEDKEY

If specified, the scan code was preceded by a prefix byte having the value 0xE0 (224).

KEYEVENTF_KEYUP

If specified, the key is being released. If not specified, the key is being depressed.

dwExtraInfo

[in] Specifies an additional value associated with the key stroke.

Return Value

This function has no return value.

Remarks

An application can simulate a press of the PRINTSCRN key in order to obtain a screen snapshot and save it to the clipboard. To do this, call keybd_event with the bVk parameter set to VK_SNAPSHOT.

Windows NT/2000/XP: The keybd_event function can toggle the NUM LOCK, CAPS LOCK, and SCROLL LOCK keys.

Windows 95/98/Me: The keybd_event function can toggle only the CAPS LOCK and SCROLL LOCK keys. It cannot toggle the NUM LOCK key.

The following sample program toggles the NUM LOCK light by using keybd_event() with a virtual key of VK_NUMLOCK. It takes a Boolean value that indicates whether the light should be turned off (FALSE) or on (TRUE). The same technique can be used for the CAPS LOCK key (VK_CAPITAL) and the SCROLL LOCK key (VK_SCROLL).

Copy Code

   #include <windows.h>   void SetNumLock( BOOL bState )   {      BYTE keyState[256];      GetKeyboardState((LPBYTE)&keyState);      if( (bState && !(keyState[VK_NUMLOCK] & 1)) ||          (!bState && (keyState[VK_NUMLOCK] & 1)) )      {      // Simulate a key press         keybd_event( VK_NUMLOCK,                      0x45,                      KEYEVENTF_EXTENDEDKEY | 0,                      0 );      // Simulate a key release         keybd_event( VK_NUMLOCK,                      0x45,                      KEYEVENTF_EXTENDEDKEY | KEYEVENTF_KEYUP,                      0);      }   }   void main()   {      SetNumLock( TRUE );   }

Function Information