在节点边缘上对齐标记 D3 强制布局

Question

我正在尝试实现 d3 强制布局，但不知道如何以正确的方式定位我的链接标记。

这是我目前得到的：

var links = force_data.force_directed_data.links;

        var nodes = {};

        // Compute the distinct nodes from the links.
        links.forEach(function (link) {
            link.source = nodes[link.source] || (nodes[link.source] = {name: link.source});
            link.target = nodes[link.target] || (nodes[link.target] = {name: link.target});
        });

        console.log(nodes);

        var width = 1000,
            height = 1000;

        var force = d3.layout.force()
            .nodes(d3.values(nodes))
            .links(links)
            .size([width, height])
            .linkDistance(300)
            .charge(-120)
            .friction(0.9)
            .on("tick", tick)
            .start();

        var svg = d3.select("#force-graph").append("svg")
            .attr("width", width)
            .attr("height", height);

        // Per-type markers, as they don't inherit styles.
        svg.append("defs").selectAll("marker")
            .data(["dominating"])
            .enter().append("marker")
            .attr("id", function (d) {
                return d;
            })
            .attr("viewBox", "0 -5 10 10")
            .attr("refX", 15)
            .attr("refY", -1.5)
            .attr("markerWidth", 12)
            .attr("markerHeight", 12)
            .attr("orient", "auto")
            .append("path")
            .attr("d", "M0,-5L10,0L0,5");

        svg.append("defs").selectAll("marker")
            .data(["concomidant"])
            .enter().append("marker")
            .attr("id", function (d) {
                return d;
            })
            .attr("viewBox", "0 -5 10 10")
            .attr("refX", 15)
            .attr("refY", -1.5)
            .attr("markerWidth", 12)
            .attr("markerHeight", 12)
            .attr("orient", "auto-start-reverse")
            .append("path")
            .attr("d", "M0,-5L10,0L0,5");

        var path = svg.append("g").selectAll("path")
            .data(force.links())
            .enter().append("path")
            .attr("class", function (d) {
                return "link " + d.type;
            })
            .attr("marker-end", function (d) {
                return "url(#" + d.type + ")";
            })
            .attr("marker-start", function (d) {
                if (d.type == "concomidant") {
                    return "url(#" + d.type + ")";
                }
            });


        var circle = svg.append("g").selectAll("circle")
            .data(force.nodes())
            .enter().append("circle")
            .attr("r", function (d) {
                return d.weight * 4;
            })
            .call(force.drag);

        var text = svg.append("g").selectAll("text")
            .data(force.nodes())
            .enter().append("text")
            .attr("x", 8)
            .attr("y", ".31em")
            .text(function (d) {
                return d.name;
            });

        // Use elliptical arc path segments to doubly-encode directionality.
        function tick() {
            path.attr("d", linkArc);
            circle.attr("transform", transform);
            text.attr("transform", transform);
        }

        function linkArc(d) {
            var dx = d.target.x - d.source.x,
                dy = d.target.y - d.source.y,
                dr = Math.sqrt(dx * dx + dy * dy);

            return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + d.target.x + "," + d.target.y;
        }

        function transform(d) {
            return "translate(" + d.x + "," + d.y + ")";
        }

为不同的链接添加不同类型的标记可以正常工作，但是如果节点变大（根据它们的权重），标记会被节点覆盖。

这是现在的截图：

有没有办法将我的标记准确地定位在节点的边缘？

Answer 1

有趣的问题。这通过正常设置链接路径，然后通过将长度回退到圆的半径来重新计算结束位置来工作。

首先在标记 def 中，将 refX 和 refY 设置为 0（这是它留在圆圈外的当前方式）：

  .attr("refX", 0)
  .attr("refY", 0)

然后做：

function tick() {

  // fit path like you've been doing
  path.attr("d", function(d){
    var dx = d.target.x - d.source.x,
        dy = d.target.y - d.source.y,
        dr = Math.sqrt(dx * dx + dy * dy);
    return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + d.target.x + "," + d.target.y;
  });

  // recalculate and back off the distance
  path.attr("d", function(d) {

    // length of current path
    var pl = this.getTotalLength(),
        // radius of circle plus marker head
        r = (d.target.weight) * 4 + 16.97, //16.97 is the "size" of the marker Math.sqrt(12**2 + 12 **2)
        // position close to where path intercepts circle
        m = this.getPointAtLength(pl - r);          

     var dx = m.x - d.source.x,
        dy = m.y - d.source.y,
        dr = Math.sqrt(dx * dx + dy * dy);

      return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + m.x + "," + m.y;
  });

  circle.attr("transform", transform);
  text.attr("transform", transform);
}

运行代码：

<!DOCTYPE html>
<html>

<head>
  <script data-require="d3@3.5.17" data-semver="3.5.17" src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.js"></script>
  <style>
    path.link {
      fill: none;
      stroke: #666;
      stroke-width: 1.5px;
    }
    
    circle {
      fill: #ccc;
      stroke: #fff;
      stroke-width: 1.5px;
    }
    
    text {
      fill: #000;
      font: 10px sans-serif;
      pointer-events: none;
    }
  </style>
</head>

<body>
  <script>
    var links = [{
      "source": "Harry",
      "target": "Sally",
      "value": "1.2"
    }, {
      "source": "Harry",
      "target": "Mario",
      "value": "1.3"
    }, {
      "source": "Sarah",
      "target": "Alice",
      "value": "0.2"
    }, {
      "source": "Eveie",
      "target": "Alice",
      "value": "0.5"
    }, {
      "source": "Peter",
      "target": "Alice",
      "value": "1.6"
    }, {
      "source": "Mario",
      "target": "Alice",
      "value": "0.4"
    }, {
      "source": "James",
      "target": "Alice",
      "value": "0.6"
    }, {
      "source": "Harry",
      "target": "Carol",
      "value": "0.7"
    }, {
      "source": "Harry",
      "target": "Nicky",
      "value": "0.8"
    }, {
      "source": "Bobby",
      "target": "Frank",
      "value": "0.8"
    }, {
      "source": "Alice",
      "target": "Mario",
      "value": "0.7"
    }, {
      "source": "Harry",
      "target": "Alice",
      "value": "0.5"
    }, {
      "source": "Sarah",
      "target": "Alice",
      "value": "1.9"
    }, {
      "source": "Roger",
      "target": "Alice",
      "value": "1.1"
    }];

    var nodes = {};

    // Compute the distinct nodes from the links.
    links.forEach(function(link) {
      link.type = "dominating";
      link.source = nodes[link.source] || (nodes[link.source] = {
        name: link.source
      });
      link.target = nodes[link.target] || (nodes[link.target] = {
        name: link.target
      });
    });

    var width = 500,
      height = 500;

    var force = d3.layout.force()
      .nodes(d3.values(nodes))
      .links(links)
      .size([width, height])
      .linkDistance(300)
      .charge(-120)
      .friction(0.9)
      .on("tick", tick)
      .start();

    var svg = d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height);

    // Per-type markers, as they don't inherit styles.
    svg.append("defs").selectAll("marker")
      .data(["dominating"])
      .enter().append("marker")
      .attr("id", function(d) {
        return d;
      })
      .attr("viewBox", "0 -5 10 10")
      .attr("refX", 0)
      .attr("refY", 0)
      .attr("markerWidth", 12)
      .attr("markerHeight", 12)
      .attr("orient", "auto")
      .append("path")
      .attr("d", "M0,-5L10,0L0,5");

    svg.append("defs").selectAll("marker")
      .data(["concomidant"])
      .enter().append("marker")
      .attr("id", function(d) {
        return d;
      })
      .attr("viewBox", "0 -5 10 10")
      .attr("refX", 0)
      .attr("refY", 0)
      .attr("markerWidth", 12)
      .attr("markerHeight", 12)
      .attr("orient", "auto-start-reverse")
      .append("path")
      .attr("d", "M0,-5L10,0L0,5");

    var path = svg.append("g").selectAll("path")
      .data(force.links())
      .enter().append("path")
      .attr("class", function(d) {
        return "link " + d.type;
      })
      .attr("marker-end", function(d) {
        return "url(#" + d.type + ")";
      })
      .attr("marker-start", function(d) {
        if (d.type == "concomidant") {
          return "url(#" + d.type + ")";
        }
      });


    var circle = svg.append("g").selectAll("circle")
      .data(force.nodes())
      .enter().append("circle")
      .attr("r", function(d) {
        return d.weight * 4;
      })
      .call(force.drag);

    var text = svg.append("g").selectAll("text")
      .data(force.nodes())
      .enter().append("text")
      .attr("x", 8)
      .attr("y", ".31em")
      .text(function(d) {
        return d.name;
      });

    function tick() {
      path.attr("d", function(d){
        var dx = d.target.x - d.source.x,
            dy = d.target.y - d.source.y,
            dr = Math.sqrt(dx * dx + dy * dy);
        return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + d.target.x + "," + d.target.y;
      });
      path.attr("d", function(d) {
        var pl = this.getTotalLength(),
          r = (d.target.weight) * 4 + 16.97, //16.97 is the "size" of the marker Math.sqrt(12**2 + 12 **2)
          m = this.getPointAtLength(pl - r);

         var dx = m.x - d.source.x,
            dy = m.y - d.source.y,
            dr = Math.sqrt(dx * dx + dy * dy);

          return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + m.x + "," + m.y;
      });
      circle.attr("transform", transform);
      text.attr("transform", transform);
    }
    

    function transform(d) {
      return "translate(" + d.x + "," + d.y + ")";
    }
  </script>
</body>

</html>