Question

I am developing a Delphi application.
On TImage.MouseDown event I want to do X task if shift key is pressed, Y task if control key is pressed and Z task if any of them is not pressed. For that I am using TShiftState variable. Now I have a function in which I have to pass this variable as parameter.

procedure Something(keyState : TShiftState);

Now In this function what I should right to check the state of key?

if KeyState <> ssShift then begin

end;

The above code shows error.
Thanks.

Answer 1

IIUC you want the empty set []:

Something([ssShift]); // X
Something([ssCtrl]); // Y
Something([]); // Z

Regarding your update:

procedure Something(keyState : TShiftState);
begin
  if ssShift in KeyState then // KeyState contains ssShift (and maybe more)
    X;
  if ssCtrl in KeyState then // KeyState contains ssCtrl (and maybe more)
    Y;
  if [ssShift, ssCtrl] * KeyState = [] then // KeyState contains neither ssShift nor ssCtrl
    Z;
end;

If you are only interested in ssShift and ssCtrl, and the other values (ssAlt, ssLeft, …) don’t matter, you can mask the latter ones out:

procedure Something(keyState : TShiftState);
var
  MaskedKeyState : TShiftState
begin
  MaskedKeyState := KeyState * [ssShift, ssCtrl];
  if ssShift in MaskedKeyState then // MaskedKeyState contains ssShift
    X;
  if ssCtrl in MaskedKeyState then // MaskedKeyState contains ssCtrl
    Y;
  if MaskedKeyState = [] then // MaskedKeyState contains neither ssShift nor ssCtrl
    Z;
end;