Requests ownership of (locks) the physical display buffer.

#define INCL_VIO
#include <os2.h>

ULONG     WaitFlag;   /*  Wait until screen I/O can take place. */
PUCHAR    Status;     /*  Address of the lock status. */
HVIO      VioHandle;  /*  VIO presentation-space handle. */
APIRET    rc;         /*  Return code. */

rc = VioScrLock(WaitFlag, Status, VioHandle);