PRB: Cannot Center Explorer-Style FileOpen Common Dialog Box

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Code Sample Modification of Win32 SDK COMDLG32 Sample

   BOOL NEAR PASCAL TestNotify(HWND hDlg, LPOFNOTIFY pofn)
   {
    switch (pofn->hdr.code)
    {

        case CDN_INITDONE:
        {
           CenterWindow (GetParent (hDlg), NULL);
           break;
        }

        :
        :
   }

   // Center with respect to another window.
   // Specifying NULL for hwndParent centers hwndChild relative to the
   // screen.
   BOOL CenterWindow(HWND hwndChild, HWND hwndParent)
   {
       RECT    rcChild, rcParent;
       int     cxChild, cyChild, cxParent, cyParent;
       int     cxScreen, cyScreen, xNew, yNew;
       HDC     hdc;

       // Get the Height and Width of the child window.
       GetWindowRect(hwndChild, &rcChild);
       cxChild = rcChild.right - rcChild.left;
       cyChild = rcChild.bottom - rcChild.top;


       if (hwndParent)
       {
       // Get the Height and Width of the parent window.
          GetWindowRect(hwndParent, &rcParent);
          cxParent = rcParent.right - rcParent.left;
          cyParent = rcParent.bottom - rcParent.top;
       }

       else
       {
          cxParent = GetSystemMetrics (SM_CXSCREEN);
          cyParent = GetSystemMetrics (SM_CYSCREEN);
          rcParent.left = 0;
          rcParent.top  = 0;
          rcParent.right = cxParent;
          rcParent.bottom= cyParent;
       }

       // Get the display limits.
       hdc = GetDC(hwndChild);
       cxScreen = GetDeviceCaps(hdc, HORZRES);
       cyScreen = GetDeviceCaps(hdc, VERTRES);
       ReleaseDC(hwndChild, hdc);

       // Calculate new X position, then adjust for screen.
       xNew = rcParent.left + ((cxParent - cxChild) / 2);
       if (xNew < 0)
       {
           xNew = 0;
       }
       else if ((xNew + cxChild) > cxScreen)
       {
           xNew = cxScreen - cxChild;
       }

       // Calculate new Y position, then adjust for screen.
       yNew = rcParent.top  + ((cyParent - cyChild) / 2);
       if (yNew < 0)
       {
           yNew = 0;
       }
       else if ((yNew + cyChild) > cyScreen)
       {
           yNew = cyScreen - cyChild;
       }

       // Set it, and return.
       return SetWindowPos(hwndChild,
                           NULL,
                           xNew, yNew,
                           0, 0,
                           SWP_NOSIZE | SWP_NOZORDER);
   }