Windows edges got clipped off

I don’t know if anybody came across this problem. However I found that in many OpenGL programmes out there including my own has the clipped problem. The clipped problem symtims are…

  1. it only happens in Double Buffering mode. Same code doesn’t fail in Single-Buffering mode.
  2. View is clipped on the right side and bottom side.
  3. The part got clipped shows always black no matter what background color you have.
  4. It happens to all types of Windows OS such as Windows 2000, NT4, ME, Windows 98.
  5. The clipped-off happens on different systems and different video cards.
  6. The width and height of the OnSize() is always matching the glViewport() size.