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How do i set NUMLOCK OFF

Posted on 1998-12-17
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Last Modified: 2010-04-04
How can i set numlock on when my program start running. This should switch on the numlock light. SetKeyboardState
only sets the program not the system keyboard buffer.
Assembler code generate GPF on my NT system. I am using
NT4 and delphi3 client server on my system.
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Question by:dziedzir
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Author Comment

by:dziedzir
ID: 1351731
Edited text of question
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rwilson032697 earned 50 total points
ID: 1351732
Use the keybd_event API function. Here is the API help for it:

Cheers,

Raymond.

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 Value

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.

See Also

GetAsyncKeyState, GetKeyState, MapVirtualKey, SetKeyboardState

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Expert Comment

by:rwilson032697
ID: 1351733
... Set bVK to VK_NUMLOCK ...

Cheers,

Raymond.
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LVL 5

Expert Comment

by:ronit051397
ID: 1351734
There are at list 2 methods (tested on D3, NT4):

procedure TForm1.Button1Click(Sender: TObject);
begin
  keybd_event(VK_NUMLOCK,0,0,0);
  keybd_event(VK_NUMLOCK,0,KEYEVENTF_KEYUP,0);
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  TmpKeyBuffer:    TKeyboardState;
  TmpScan:         Integer;
begin
 GetKeyboardState(TmpKeyBuffer);
  SetKeyboardState(TmpKeyBuffer);
  TmpScan := MapVirtualKey(VK_NUMLOCK,0);
  Keybd_event(VK_NUMLOCK,TmpScan,0,0);
  Keybd_event(VK_NUMLOCK,TmpScan,KEYEVENTF_KEYUP,0);
end;

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Author Comment

by:dziedzir
ID: 1351735
Thanks a lot for your help.

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