This function maps points from dialog coordinates to window coordinates, or from window coordinates to dialog coordinates.

#define INCL_WINDIALOGS /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HWND       hwndDlg;            /*  Dialog-window handle. */
PPOINTL    prgwptl;            /*  Coordinate points to be mapped. */
ULONG      cwpt;               /*  Number of coordinate points. */
BOOL       fCalcWindowCoords;  /*  Calculation control. */
BOOL       rc;                 /*  Coordinates-mapped indicator. */

rc = WinMapDlgPoints(hwndDlg, prgwptl, cwpt,
       fCalcWindowCoords);