keybd_event详解

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.

VOID keybd_event(

    BYTE bVk, // virtual-key code
    BYTE bScan, // hardware scan code
    DWORD dwFlags, // flags specifying various function options
    DWORD dwExtraInfo  // additional data associated with keystroke
   ); 
 

Parameters

bVk

Specifies a virtual-key code. The code must be a value in the range 1 to 254.

bScan

Specifies a hardware scan code for the key.

dwFlags

A set of flag bits that specify various aspects of function operation. An application can use any combination of the following predefined constant values to set the flags:

Value Meaning
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

Specifies an additional 32-bit value associated with the key stroke.

 

Return Values

This function has no return value.

Remarks

Although keybd_event passes an OEM-dependent hardware scan code to Windows, applications should not use the scan code. Windows converts scan codes to virtual-key codes internally and clears the up/down bit in the scan code before passing it to applications.
An application can simulate a press of the PRINTSCREEN key in order to obtain a screen snapshot and save it to the Windows clipboard. To do this, call keybd_event with the bVk parameter set to VK_SNAPSHOT, and the bScan parameter set to 0 for a snapshot of the full screen or set bScan to 1 for a snapshot of the active window.