title: Drawing on the screen
body: <p>I'm currently developing an application with OpenCV to do visual recognition of elements on the screen.</p>
  
  <p>While a visual representation of the process is not needed, it would be very useful for debugging purposes if I could find a way to draw circles, lines and possibly text directly on the screen, without having an app window.</p>
  
  <p>There are certain applications that, for instance, draw HUDs over the screen. How do they go about doing that?</p>
  
  <p>I need a way for my drawing to always be at the front. In general, all the ways I managed to find involve painting on a window (WinAPI, Direct2D, OpenGL). Is there a workaround to make it appear like it's simply a layover on the desktop (including all open windows)?</p>