This example fills an update rectangle with a white background in response to the WM_PAINT message, after obtaining a presentation space handle via WinBeginPaint.

#define INCL_WINWINDOWMGR       /* Window Manager Functions     */
#include <os2.h>

BOOL  fSuccess;         /* success indicator                    */
HAB     hab;            /* anchor-block handle                  */
PRECTL prclRect1 = {0,0,100,100}; /* fill rectangle              */
LONG  lColor=CLR_WHITE; /* fill color                           */
HWND   hwnd;            /* client window handle                 */
HPS    hps;             /* presentation-space handle            */

case WM_PAINT:
     hps = WinBeginPaint(hwnd, NULLHANDLE, &prclRect1);
     fSuccess = WinFillRect(hps, &prclRect1, lColor);
     WinEndPaint(hps);