This message is sent when an operator presses a key.

param1
     USHORT  fsflags     /*  Keyboard control codes. */
     UCHAR   ucrepeat    /*  Repeat count. */
     UCHAR   ucscancode  /*  Hardware scan code. */

param2
     USHORT  usch        /*  Character code. */
     USHORT  usvk        /*  Virtual key codes. */