The following example demonstrates procedures that provide the capibility of sending keystrokes to any window control capable of receiving keyboard input. You may use this technique to toggle the num lock, caps lock, and scroll lock keys under Windows NT. This same technique works for toggling caps lock and scroll lock keys under Windows 95, but it will not work for num lock.

Note that there are four procedures provided: SimulateKeyDown(), SimulateKeyUp(), SimulateKeystroke(), and SendKeys(), to allow greater control in your ability to send keystrokes.

The SimulateKeyDown(), SimulateKeyUp(), and SimulateKeystroke() procedures expect a virtural key code (like VK_F ). The SimulateKeystroke() procedure accepts an extra parameter that is useful when simulating the PrintScreen key. When extra is set to zero, the entire screen will be captured to the windows clipboard. When extra is set to one, only the active window will be captured.

The four button click methods demonstrate the use of these functions: ButtonClick - Toggles the cap lock. ButtonClick2 - Captures the entire screen to the clipboard. ButtonClick3 - Capture the active window to the clipboard. ButtonClick4 - Set the focus to an edit control and sends it a string.

Example:

procedure SimulateKeyDown(Key : byte); begin keybd_event(Key, 0, 0, 0); end;

procedure SimulateKeyUp(Key : byte); begin keybd_event(Key, 0, KEYEVENTF_KEYUP, 0); end;

procedure SimulateKeystroke(Key : byte; extra : DWORD); begin keybd_event(Key, extra, 0, 0); keybd_event(Key, extra, KEYEVENTF_KEYUP, 0); end;

procedure SendKeys(s : string); var i : integer; flag : bool; w : word; begin {Get the state of the caps lock key} flag := not GetKeyState(VK_CAPITAL) and = 0; {If the caps lock key is on then turn it off} if flag then SimulateKeystroke(VK_CAPITAL, 0); for i := to Length(s) do begin w := VkKeyScan(s[i]); {If there is not an error in the key translation} if ((HiByte(w) <> $FF) and (LoByte(w) <> $FF)) then begin {If the key requires the shift key down - hold it down} if HiByte(w) and = then SimulateKeyDown(VK_SHIFT); {Send the VK_KEY} SimulateKeystroke(LoByte(w), 0); {If the key required the shift key down - release it} if HiByte(w) and = then SimulateKeyUp(VK_SHIFT); end; end; {if the caps lock key was on at start, turn it back on} if flag then SimulateKeystroke(VK_CAPITAL, 0); end;

procedure TForm .Button Click(Sender: TObject); begin {Toggle the cap lock} SimulateKeystroke(VK_CAPITAL, 0); end;

procedure TForm .Button2Click(Sender: TObject); begin {Capture the entire screen to the clipboard} {by simulating pressing the PrintScreen key} SimulateKeystroke(VK_SNAPSHOT, 0); end;

procedure TForm .Button3Click(Sender: TObject); begin {Capture the active window to the clipboard} {by simulating pressing the PrintScreen key} SimulateKeystroke(VK_SNAPSHOT, ); end;

procedure TForm .Button4Click(Sender: TObject); begin {Set the focus to a window (edit control) and send it a string} Application.ProcessMessages; Edit .SetFocus; SendKeys('Delphi Is RAD!'); end;

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