Dynamic in-game object creation and manipulation

[Tomi]

Is the right place for drawing objects the FormPaint event? I have put the following piece of code there, but the bullets aren't visible. Only the background and the player's spaceship are visible. What is wrong?

procedure TMain.FormPaint(Sender: TObject);
  var i: integer;
begin
 //Canvas.clear;
  Canvas.StretchDraw(Rect(0, 0, ClientWidth, ClientHeight), backg);
  if numofbullets>1 then
  begin
       for i:=1 to numofbullets-1 do
       begin
        if bullets[i]<>nil then
           Canvas.Draw(bullets[i].xplace,bullets[i].yplace,bullets[i].picture);
       end;
  end;
end;