WM_ERASEBKGND

  This message is sent to a window before it's client area is about to be
erased. The default action is to erase the window. If an application wants
to perform its own erasing, then it should process the WM_ERASEBACKGROUND
message and return TRUE. If an application is not interested in this
message, the window procedure should return FALSE.

Parameters
  wParam is not used.
  lParam is not used.