title: How to overlay graphics on Windows games?
body: <p>I want my program to be able to launch any Windows game, and while the user is playing it, intermittently display some text or pictures in some part of the game window. The game may be in windowed or full-screen mode. From what I have been able to figure out from online resources, this could be done using a graphics library that supports overlays and using Windows Hooks to keep track of the target application's window. In this context I have some questions. </p>
  
  <ol>
  <li>Will the overlays affect the game's performance?</li>
  <li>How will hooking the application affect performance?</li>
  <li>Is there any other way one could achieve this? For example, how do you think <a href="http://msdn.microsoft.com/en-us/library/ee417062(VS.85).aspx" rel="noreferrer">PIX</a>, the DirectX debugging and analysis tool, work?  </li>
  </ol>