This message was posted on behalf of Intel Corporation
I understand you are trying to find out why black afterimage remains when the wglChoosePixelFormatARB funtion is called.
Let me apologize for any inconvenience this issue may be causing to you.
I recommend contacting our graphics developers so they can assist you better. This link will give you their contact information https://software.intel.com/en-us/forums/developing-games-and-graphics-on-intel