This example shows how to center a dialog box within the Screen using WinQueryWindowPos.

#define INCL_WINWINDOWMGR
#define INCL_WINSYS
#include <OS2.H>
HWND  hwnd;           /* window handle. */
SHORT ix, iy;
SHORT iwidth, idepth;
SWP   swp;

  /* Query width and height of Screen device                         */
  iwidth = WinQuerySysValue( HWND_DESKTOP, SV_CXSCREEN );
  idepth = WinQuerySysValue( HWND_DESKTOP, SV_CYSCREEN );

  /* Query width and height of dialog box                            */
  WinQueryWindowPos( hwnd, (PSWP)&swp );

  /* Center dialog box within the Screen                             */
  ix = (SHORT)(( iwidth  - swp.cx ) / 2);
  iy = (SHORT)(( idepth  - swp.cy ) / 2);
  WinSetWindowPos( hwnd, HWND_TOP, ix, iy, 0, 0, SWP_MOVE );