This function obtains a presentation space whose associated update region is set ready for drawing in a specified window.

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

HWND      hwnd;        /*  Handle of window where drawing is going to occur. */
HPS       hps;         /*  Presentation-space handle. */
PRECTL    prclPaint;   /*  Bounding rectangle. */
HPS       hpsPaintPS;  /*  Presentation-space handle. */

hpsPaintPS = WinBeginPaint(hwnd, hps, prclPaint);