1. Technology

Simulating keystrokes from code

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Here's a handy function to simulate the pressing of keyboard keys.

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procedure PostKeyEx32(key: Word; const shift: TShiftState; specialkey: Boolean) ;
{
Parameters :
* key : virtual keycode of the key to send. For printable keys this is simply the ANSI code (Ord(character)) .
* shift : state of the modifier keys. This is a set, so you can set several of these keys (shift, control, alt, mouse buttons) in tandem. The TShiftState type is declared in the Classes Unit.
* specialkey: normally this should be False. Set it to True to specify a key on the numeric keypad, for example.

Description:
Uses keybd_event to manufacture a series of key events matching the passed parameters. The events go to the control with focus. Note that for characters key is always the upper-case version of the character. Sending without any modifier keys will result in a lower-case character, sending it with [ ssShift ] will result in an upper-case character!
}
type
   TShiftKeyInfo = record
     shift: Byte ;
     vkey: Byte ;
   end;
   ByteSet = set of 0..7 ;
const
   shiftkeys: array [1..3] of TShiftKeyInfo =
     ((shift: Ord(ssCtrl) ; vkey: VK_CONTROL),
     (shift: Ord(ssShift) ; vkey: VK_SHIFT),
     (shift: Ord(ssAlt) ; vkey: VK_MENU)) ;
var
   flag: DWORD;
   bShift: ByteSet absolute shift;
   j: Integer;
begin
   for j := 1 to 3 do
   begin
     if shiftkeys[j].shift in bShift then
       keybd_event(shiftkeys[j].vkey, MapVirtualKey(shiftkeys[j].vkey, 0), 0, 0) ;
   end;
   if specialkey then
     flag := KEYEVENTF_EXTENDEDKEY
   else
     flag := 0;

   keybd_event(key, MapvirtualKey(key, 0), flag, 0) ;
   flag := flag or KEYEVENTF_KEYUP;
   keybd_event(key, MapvirtualKey(key, 0), flag, 0) ;

   for j := 3 downto 1 do
   begin
     if shiftkeys[j].shift in bShift then
       keybd_event(shiftkeys[j].vkey, MapVirtualKey(shiftkeys[j].vkey, 0), KEYEVENTF_KEYUP, 0) ;
   end;
end;
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Example of usage:
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procedure TForm1.SpeedButton1Click(Sender: TObject) ;
begin
// Simulate PRINTSCREEN - snapshot of the full screen
PostKeyEx32(VK_SNAPSHOT, [], False) ;

// Simulate PRINTSCREEN - snapshot of the active window
PostKeyEx32(VK_SNAPSHOT, [ssAlt], False) ;

// Simulate left Windows key
PostKeyEx32(VK_LWIN, [], False) ;

// Simulate Alt+F4 - close active window
PostKeyEx32(VK_F4, [ssAlt], False) ;
end;
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