Keyboard Events Simulation using keybd_event() function

Programming 궁금하니? 2009. 3. 31. 18:56

출처: http://www.codeproject.com/KB/system/keyboard.aspx?display=Print

Introduction

Simulation of a keyboard input is a well known concept for those who are all familiar with Visual Basic. SendKeys() in Visual Basic does all the things, if you want to do anything without keyboard. But what is in SendKeys() function? What does it do? Can we do such a thing with Visual C++? This article is the answer. I think this will be useful for beginners who are all just trying to do something different with VC++. Let us get into the steps…

Function Syntax

void keybd_event(BYTE bVirtualKey, BYTE bScanCode, 
                         DWORD dwFlags, DWORD dwExtraInfo);

bVirtualKey //Virtual Keycode of keys. E.g., VK_RETURN, VK_TAB…
bScanCode //Scan Code value of keys. E.g., 0xb8 for “Left Alt” key.
dwFlags //Flag that is set for key state. E.g., KEYEVENTF_KEYUP.
dwExtraInfo //32-bit extra information about keystroke.

Function Details:

bVirtualKey

Virtual keycode that has to be send as key input. The following are the available predefined virtual key codes:

`VK_NUMPAD7`	0x67	`VK_BACK`	0x08
`VK_NUMPAD8`	0x68	`VK_TAB`	0x09
`VK_NUMPAD9`	0x69	`VK_RETURN`	0x0D
`VK_MULTIPLY`	0x6A	`VK_SHIFT`	0x10
`VK_ADD`	0x6B	`VK_CONTROL`	0x11
`VK_SEPARATOR`	0x6C	`VK_MENU`	0x12
`VK_SUBTRACT`	0x6D	`VK_PAUSE`	0x13
`VK_DECIMAL`	0x6E	`VK_CAPITAL`	0x14
`VK_DIVIDE`	0x6F	`VK_ESCAPE`	0x1B
`VK_F1`	0x70	`VK_SPACE`	0x20
`VK_F2`	0x71	`VK_END`	0x23
`VK_F3`	0x72	`VK_HOME`	0x24
`VK_F4`	0x73	`VK_LEFT`	0x25
`VK_F5`	0x74	`VK_UP`	0x26
`VK_F6`	0x75	`VK_RIGHT`	0x27
`VK_F7`	0x76	`VK_DOWN`	0x28
`VK_F8`	0x77	`VK_PRINT`	0x2A
`VK_F9`	0x78	`VK_SNAPSHOT`	0x2C
`VK_F10`	0x79	`VK_INSERT`	0x2D
`VK_F11`	0x7A	`VK_DELETE`	0x2E
`VK_F12`	0x7B	`VK_LWIN`	0x5B
`VK_NUMLOCK`	0x90	`VK_RWIN`	0x5C
`VK_SCROLL`	0x91	`VK_NUMPAD0`	0x60
`VK_LSHIFT`	0xA0	`VK_NUMPAD1`	0x61
`VK_RSHIFT`	0xA1	`VK_NUMPAD2`	0x62
`VK_LCONTROL`	0xA2	`VK_NUMPAD3`	0x63
`VK_RCONTROL`	0xA3	`VK_NUMPAD4`	0x64
`VK_LMENU`	0xA4	`VK_NUMPAD5`	0x65
`VK_RMENU`	0xA5	`VK_NUMPAD6`	0x66

Character key can be converted into virtual key using VkKeyScan(TCHAR ch) function.

bScanCode
Scan code is the hardware key code for the key (make and break codes). The following are the available scan codes (break code will be used in this parameter).

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
32-bit extra information along with the keyboard input.

Example Code

// Simulating a Alt+Tab keystroke
keybd_event(VK_MENU,0xb8,0 , 0); //Alt Press
keybd_event(VK_TAB,0x8f,0 , 0); // Tab Press
keybd_event(VK_TAB,0x8f, KEYEVENTF_KEYUP,0); // Tab Release
keybd_event(VK_MENU,0xb8,KEYEVENTF_KEYUP,0); // Alt Release

// Simulating a Ctrl+A keystroke
keybd_event(VK_CONTROL,0x9d,0 , 0); // Ctrl Press
keybd_event(VkKeyScan(‘A’),0x9e,0 , 0); // ‘A’ Press
keybd_event(VkKeyScan(‘A’),0x9e, KEYEVENTF_KEYUP,0); // ‘A’ Release
keybd_event(VK_CONTROL,0x9d,KEYEVENTF_KEYUP,0); // Ctrl Release

Conclusion

This article may not be that much detailed. None of the articles can satisfy one's expectations. But, each article should be a seed for your technical growth. Thus, I believe that this would be a seed. Thank you all.

Discussions and Feedback

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Last Updated: 4 Jun 2004
Editor: Smitha Vijayan

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