问当用户缩小时增加Konva.js地图中的文本大小

EN

function redrawSegments(segArray){
drawLayer.destroy();
segGrp = new Konva.Group({name:'segments'});
cornGrp = new Konva.Group({name:'corners'});
tGrp = new Konva.Group({name:'tconnections'});
lenGrp = new Konva.Group({name:'lengths'});
/* SEGMENTS */
for(var i=0;i<segArray.length;i++){
    drawShape = new Konva.Line({
        points: [segArray[i].start.x, segArray[i].start.y,
                segArray[i].end.x, segArray[i].end.y],
        strokeWidth: 15,
        stroke: 'black',
        opacity: 1,
        dir:'',
        id:i
    });
    if(drawShape.attrs.points[0]==drawShape.attrs.points[2])
        drawShape.attrs.dir = 'v';
    else if(drawShape.attrs.points[1]==drawShape.attrs.points[3])
        drawShape.attrs.dir = 'h';
    drawShape.on('mouseover', function (e) {
        if(mouseMode == 1 && selSegment !== e.target.attrs.id){
            this.stroke('#092C70');
            drawLayer.draw();
        }
    });
    drawShape.on('mouseout', function (e) {
        if(mouseMode == 1 && selSegment !== e.target.attrs.id){
            this.stroke('black');
            drawLayer.draw();
        }
    });
    drawShape.on('mouseup', function (e){
        if(mouseMode == 1){
            if(selSegment !== null){
                var aux = getDesignSegByID(selSegment);
                if(aux !== -1)
                    segGrp.children[aux].stroke('black');
                selSegment = null;
            }
            selSegment = e.target.attrs.id;
            this.stroke('#264F9F');
            drawLayer.draw();
            //make delete button active
            $('#delButton').removeClass('btn_disabled');
        }
    });
    segGrp.add(drawShape);

    //Length indicator
    var lenTxt = new Konva.Text({
        align: 'center',
        verticalAlign: 'middle',
        fontSize: 12,
        resizeEnabled:true
    });        

      if(drawShape.attrs.dir === 'v'){
        lenTxt.rotation(90);
        lenTxt.x(drawShape.attrs.points[0]-18);
        lenTxt.y(drawShape.attrs.points[1]);
        if(drawShape.attrs.points[1] > drawShape.attrs.points[3])
            lenTxt.y(drawShape.attrs.points[3]);
    }else{
        //length dashed line
        lenTxt.rotation(0);                    
        lenTxt.y(drawShape.attrs.points[1]-25);
        lenTxt.x(drawShape.attrs.points[0]);
        if(drawShape.attrs.points[0] > drawShape.attrs.points[2])
            lenTxt.x(drawShape.attrs.points[2]);
    }                
    lenTot = getSegLength(segArray[i]);
    lenTxt.text(lenTot +' mm');
    lenTxt.width(lenTot/gridSizeInMM * gridSize);
    lenGrp.add(lenTxt);

}

drawLayer.add(segGrp);
drawLayer.add(lenGrp);