sprintf(m_szBuff, "%6s %1s",item_no,item_name);
这段中的item_name有时候会很长，造成打印区域过大，如何强制固定一个item_name的打印字符长度？整个类如下：
void CSaleImpl::PrintBillItem(CString item_no,CString item_name,double qty,double amnt)
{
    int nMaxLen = GetSalePos()->GetParams()->m_nMaxPrintLineLen;
    int i = 0;
    
    if ( nMaxLen < 32 )
    nMaxLen = 32;

    CPrinter *printer = GetSalePos()->GetPrinter();
    char *pt = m_szBuff;
    char *tmp=new char[512];
    char *result=new char[512];
    
    sprintf(m_szBuff, "%6s %1s",item_no,item_name);
    sprintf(tmp, "%7.f %7.02f",qty,amnt);
   
    GetPrintFormatLines(m_szBuff, tmp, result, nMaxLen);
    //GetPrintFormatAlignString(m_szBuff,m_szBuff,DT_CENTER);
    printer->PrintLine( result );
    delete []tmp;delete []result;

}