This function draws a filled rectangular area.

#define INCL_WINWINDOWMGR /* Or use INCL_WIN, INCL_PM, Also in COMMON section */
#include <os2.h>

HPS       hps;     /*  Presentation-space handle. */
PRECTL    prcl;    /*  Rectangle to be filled, in window coordinates. */
LONG      lColor;  /*  Color with which to fill the rectangle. */
BOOL      rc;      /*  Success indicator. */

rc = WinFillRect(hps, prcl, lColor);