title: (C/C++/C#) DirectX 9 Overlay, preferably the same way xfire or Steam does it
body: <p>I wonder what techniques xfire and/or Steam uses to overlay into games.
  I'm trying to do something similar and I really would like to know what is the least intrusive way, I.e. won't alert any anti-cheat systems. I don't need any kind of information from the game (no wall-hack BS). I would basically just like to display a rectangle with custom contents in the game.</p>
  
  <p>PS. I have seen some examples by googling but most of them seem very old. Are they still good options?</p>