if (iC % 50 == 0)
if (iC % 20 == 0)
mng_retcode display_progressive_check (mng_datap pData){                                      /* approximate the need for progressive display */  if (((pData->eImagetype != mng_it_mng) || (pData->iDataheight > 300)) &&      (pData->iDestb - pData->iDestt > 50) && (!pData->pCurraniobj))  {    mng_int32 iC = pData->iRow + pData->iDestt - pData->iSourcet;    if (iC % 50 == 0)                  /* every 20th line */      pData->bNeedrefresh = MNG_TRUE;  }  return MNG_NOERROR;}