code: function textLabel(x,y,s,color) {// x is center x ,y is bottom y
    var charSize=getCharSize(LABEL_FONT_SIZE);
    var lines=s.split("\n");
    var textHeight=lines.length*charSize.height;
    var textWidth;
    if (lines.length>1) {
      textWidth=Math.max.apply(Math,lines.map(function (a) {return a.length}));
    } else {
      textWidth=s.length;
    }
    textWidth=textWidth*charSize.width;
    var margin=4;
    var txt={
      type:'text',
      x:x,y:y-textHeight/2-margin,
      text:s,
      'font-size':LABEL_FONT_SIZE,
      'font-family':FONT_FAMILY,
      fill:color || '#444'
    };
    return {
      label:txt,
      x:x-textWidth/2,y:y-textHeight-margin,
      width:textWidth,height:textHeight+margin
    };
  }
docs: return LabelObject {lable:Element,x,y,width,height}