Simulation support:

This function is mandatory for display drivers that want to be DCAF-enabled.

Description GreOpenScreenChangeArea allocates a data area internal to the display driver, in which the driver will accumulate screen changes. The function returns a 32-bit handle that is required to identify the area in GreGetScreenChangeArea and GreCloseScreenChangeArea calls.

#define INCL_GRE_SCREEN
#include <os2.h>
#include <pmddi.h>

HDC      hdc;     /*  Any device context handle. */
PDC      pdcArg;  /*  Pointer to instance data. */
ULONG    FunN;    /*  High-order word=Flags; Low-order word=NGreOpenScreenChangeArea. */
LONG     rc;

rc = GreOpenScreenChangeArea(hdc, pdcArg,
       FunN);