javascript - 附加文本未显示在 d3 v4 中

Question

我正在尝试“翻译”parallel coordinates example到新版本的d3 v4。我有一个使用此 javascript 的工作示例(如果有人尝试使用 d3 的 v4 并且对新功能有疑问，这也是一个很好的示例):

var margin = {top: 30, right: 10, bottom: 10, left: 10},
    width = 600 - margin.left - margin.right,
    height = 200 - margin.top - margin.bottom;

var x = d3.scaleBand().rangeRound([0, width]).padding(1),
    y = {},
    dragging = {};


var line = d3.line(),
    //axis = d3.axisLeft(x),
    background,
    foreground,
    extents;

var svg = d3.select("#body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

d3.csv("cars.csv", function(error, cars) {
  // Extract the list of dimensions and create a scale for each.
    //cars[0] contains the header elements, then for all elements in the header
    //different than "name" it creates and y axis in a dictionary by variable name
  x.domain(dimensions = d3.keys(cars[0]).filter(function(d) {
    if(d == "name") {
        return false;
    }
    return y[d] = d3.scaleLinear()
        .domain(d3.extent(cars, function(p) { 
            return +p[d]; }))
        .range([height, 0]);
  }));

  extents = dimensions.map(function(p) { return [0,0]; });

  // Add grey background lines for context.
  background = svg.append("g")
      .attr("class", "background")
    .selectAll("path")
      .data(cars)
    .enter().append("path")
      .attr("d", path);

  // Add blue foreground lines for focus.
  foreground = svg.append("g")
      .attr("class", "foreground")
    .selectAll("path")
      .data(cars)
    .enter().append("path")
      .attr("d", path);

  // Add a group element for each dimension.
  var g = svg.selectAll(".dimension")
      .data(dimensions)
    .enter().append("g")
      .attr("class", "dimension")
      .attr("transform", function(d) {  return "translate(" + x(d) + ")"; })
      .call(d3.drag()
        .subject(function(d) { return {x: x(d)}; })
        .on("start", function(d) {
          dragging[d] = x(d);
          background.attr("visibility", "hidden");
        })
        .on("drag", function(d) {
          dragging[d] = Math.min(width, Math.max(0, d3.event.x));
          foreground.attr("d", path);
          dimensions.sort(function(a, b) { return position(a) - position(b); });
          x.domain(dimensions);
          g.attr("transform", function(d) { return "translate(" + position(d) + ")"; })
        })
        .on("end", function(d) {
          delete dragging[d];
          transition(d3.select(this)).attr("transform", "translate(" + x(d) + ")");
          transition(foreground).attr("d", path);
          background
              .attr("d", path)
            .transition()
              .delay(500)
              .duration(0)
              .attr("visibility", null);
        }));
  // Add an axis and title.
  g.append("g")
      .attr("class", "axis")
      .each(function(d) {  d3.select(this).call(d3.axisLeft(y[d]));})
      //text does not show up because previous line breaks somehow
    .append("text")
      .style("text-anchor", "middle")
      .attr("y", -9)
      .text(function(d) { return d; });

  // Add and store a brush for each axis.
  g.append("g")
      .attr("class", "brush")
      .each(function(d) {
        d3.select(this).call(y[d].brush = d3.brushY().extent([[-8, 0], [8,height]]).on("brush start", brushstart).on("brush", brush_parallel_chart));
      })
    .selectAll("rect")
      .attr("x", -8)
      .attr("width", 16);
});

function position(d) {
  var v = dragging[d];
  return v == null ? x(d) : v;
}

function transition(g) {
  return g.transition().duration(500);
}

// Returns the path for a given data point.
function path(d) {
  return line(dimensions.map(function(p) { return [position(p), y[p](d[p])]; }));
}

function brushstart() {
  d3.event.sourceEvent.stopPropagation();
}


// Handles a brush event, toggling the display of foreground lines.
function brush_parallel_chart() {    
    for(var i=0;i<dimensions.length;++i){
        if(d3.event.target==y[dimensions[i]].brush) {
            extents[i]=d3.event.selection.map(y[dimensions[i]].invert,y[dimensions[i]]);

        }
    }

      foreground.style("display", function(d) {
        return dimensions.every(function(p, i) {
            if(extents[i][0]==0 && extents[i][0]==0) {
                return true;
            }
          return extents[i][1] <= d[p] && d[p] <= extents[i][0];
        }) ? null : "none";
      });
}

一切正常(刷在每个轴上，改变轴的顺序......)除了每个轴顶部的标签没有显示，即使附加了文本标签并且文本是写在标签中(可以通过使用浏览器检查生成的 html 来检查)。我相信负责这部分的代码是这部分，但我无法找到发生这种情况的原因:

  g.append("g")
      .attr("class", "axis")
      .each(function(d) {  d3.select(this).call(d3.axisLeft(y[d]));})
      //text does not show up because previous line breaks somehow
    .append("text")
      .style("text-anchor", "middle")
      .attr("y", -9)
      .text(function(d) { return d; });

为什么文本标签不显示？

Answer 1

在 D3 v4 中，轴组件将显式设置填充为 none在它被要求的选择上。来自source code :

selection.filter(entering)
    .attr("fill", "none")      // <=== Fill set to none by D3
    .attr("font-size", 10)
    .attr("font-family", "sans-serif")
    .attr("text-anchor", orient === right ? "start" : orient === left ? "end" : "middle");

这将创建以下代码:

对比v3生成的代码:

<text>元素将继承这些属性，因为它们是这些组的子元素，因此隐藏了文本。

要显示标签，您需要明确设置它们的样式，这是可以做到的

1. 通过 CSS:

   .axis text {
     fill:black;   /* <== Set the fill */
     text-shadow: 0 1px 0 #fff, 1px 0 0 #fff, 0 -1px 0 #fff, -1px 0 0 #fff;
     cursor: move;
   }
   

   工作 demo .

2. 通过设置 fill <text> 上的属性元素本身:

   .append("text")
     .attr("fill", "black")          // <=== Set the fill
   //  .style("fill", "black")       // Will also work when using .style()
     .style("text-anchor", "middle")
     .attr("y", -9) 
     .text(function(d) { return d; });
   

   工作 demo .