How to make a shape jump when pressing Up key

Question

I'd like to make a shape jump when the player presses the UP key, so the best i could think of is this, but the method i used is terrible and problematic:

(shape coordinates: shape1.top:=432;)

procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
case key of
vk_up: shape1.top:=shape1.top-40   //so that it jumps to 392
end; 
end;

And now this timer:

procedure TForm1.Timer1Timer(Sender: TObject);
begin
timer1.interval:=300
if shape1.Top<400 then      //if shape1.top=392 < 400
begin
shape1.Top:=432;            //move back to 432
end;

end;

The problem is that players can constantly press the key UP, which I don't want. I know this method is terrible, so i hope you have something better than this and i would be grateful if you could share it with me.

Answer 1

If the player can hold down a key and KeyDown fires repeatedly, you can lock it.

First, declare a field on the form called FKeyLock: set of byte. (Note: this technique will fail if you get any Key values higher than 255, but the ones you're likely to deal with won't be that high.)

procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
  if key in FKeyLock then
    Exit;
  case key of
    vk_up:
    begin
      shape1.top:=shape1.top-40;   //so that it jumps to 392
      include(FKeyLock, vk_up);
    end;
  end;
end;

procedure TForm1.FormKeyUp(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
   exclude(FKeyLock, key);
end;