G6的插件系统做的相当完善, 可惜文档没有具体说到. 这里整理一下g6的插件.

插件大致分为四种类型:

1. behaviour 行为, 可以理解为事件处理
2. node, edge的插件, 就是node和edge的样式, 同样是插件
3. layout插件, node的布局之类, 这部分涉及的算法比较多
4. Util插件, 就是自定义工具函数, 将其内置G6.Util中

这四种插件都有各自的写法以及api, 但是文档中没有提到, 这里简单介绍一下. 一下都以官方插件为例.

behaviour 行为

写完发现其实官方有这部分的文档: https://www.yuque.com/antv/g6/custom-interaction

请看下面代码, 这部分是注册一个右键拖动的行为:

// g6/plugins/behaviour.analysis/index.js
function panCanvas(graph, button = 'left', panBlank = false) {
  let lastPoint;
  if (button === 'right') {
    graph.behaviourOn('contextmenu', ev => {
      ev.domEvent.preventDefault();
    });
  }
  graph.behaviourOn('mousedown', ev => {
    if (button === 'left' && ev.domEvent.button === 0 ||
    button === 'right' && ev.domEvent.button === 2) {
      if (panBlank) {
        if (!ev.shape) {
          lastPoint = {
            x: ev.domX,
            y: ev.domY
          };
        }
      } else {
        lastPoint = {
          x: ev.domX,
          y: ev.domY
        };
      }
    }
  });


// 鼠标右键拖拽画布空白处平移画布交互
G6.registerBehaviour('rightPanBlank', graph => {
  panCanvas(graph, 'right', true);
})

然后在实例化graph的时候在modes中引入:

new Graph({
  modes: {
    default: ['panCanvas']
  }
})

其实到这里我们已经知道了, 只要是在一些内置事件中注册一下自定义事件再引入我们就可以称之为一个行为插件. 但是我们还需要再深入一点, 看到底是不是这样的.

// g6/src/mixin/mode.js
behaviourOn(type, fn) {
    const eventCache = this._eventCache;
    if (!eventCache[type]) {
      eventCache[type] = [];
    }
    eventCache[type].push(fn);
    this.on(type, fn);
},

照老虎画猫我们最终可以实现一个自己的行为插件:

// 未经过验证
function test(graph) {
 graph.behaviourOn('mousedown' () => alert(1) ) 
}


// 鼠标右键拖拽画布空白处平移画布交互
G6.registerBehaviour('test', graph => {
  test(graph);
})

new Graph({
  modes: {
    default: ['test']
  }
})

node, edge的插件

关于node, edge的插件的插件其实官方文档上面的自定义形状和自定义边.

// g6/plugins/edge.polyline/index.js
G6.registerEdge('polyline', {
  offset: 10,
  getPath(item) {
    const points = item.getPoints();
    const source = item.getSource();
    const target = item.getTarget();
    return this.getPathByPoints(points, source, target);
  },
  getPathByPoints(points, source, target) {
    const polylinePoints = getPolylinePoints(points[0], points[points.length - 1], source, target, this.offset);
    // FIXME default
    return Util.pointsToPolygon(polylinePoints);
  }
});

G6.registerEdge('polyline-round', {
  borderRadius: 9,
  getPathByPoints(points, source, target) {
    const polylinePoints = simplifyPolyline(
      getPolylinePoints(points[0], points[points.length - 1], source, target, this.offset)
    );
    // FIXME default
    return getPathWithBorderRadiusByPolyline(polylinePoints, this.borderRadius);
  }
}, 'polyline');

这部分那么多代码其实最重要的还是上面的部分, 注册一个自定义边, 直接引入就可以在shape中使用了, 具体就不展开了.
自定义边
自定义节点

layout插件

layout在初始化的时候即可以在 layout 字段中初始化也可以在plugins中.

const graph = new G6.Graph({
  container: 'mountNode',
  layout: dagre
})

/* ---- */

const graph = new G6.Graph({
  container: 'mountNode',
  plugins: [ dagre ]
})

原因在于写插件的时候同时也把布局注册为一个插件了:

// g6/plugins/layout.dagre/index.js
class Plugin {
  constructor(options) {
    this.options = options;
  }
  init() {
    const graph = this.graph;
    graph.on('beforeinit', () => {
      const layout = new Layout(this.options);
      graph.set('layout', layout);
    });
  }
}

G6.Plugins['layout.dagre'] = Plugin;

通过查看源码我们可以知道自定义布局的核心方法就是execute, 再具体一点就是我们需要在每个布局插件中都有execute方法:

// g6/plugins/layout.dagre/layout.js
// 执行布局
  execute() {
    const nodes = this.nodes;
    const edges = this.edges;
    const nodeMap = {};
    const g = new dagre.graphlib.Graph();
    const useEdgeControlPoint = this.useEdgeControlPoint;
    g.setGraph({
      rankdir: this.getValue('rankdir'),
      align: this.getValue('align'),
      nodesep: this.getValue('nodesep'),
      edgesep: this.getValue('edgesep'),
      ranksep: this.getValue('ranksep'),
      marginx: this.getValue('marginx'),
      marginy: this.getValue('marginy'),
      acyclicer: this.getValue('acyclicer'),
      ranker: this.getValue('ranker')
    });
    g.setDefaultEdgeLabel(function() { return {}; });
    nodes.forEach(node => {
      g.setNode(node.id, { width: node.width, height: node.height });
      nodeMap[node.id] = node;
    });
    edges.forEach(edge => {
      g.setEdge(edge.source, edge.target);
    });
    dagre.layout(g);
    g.nodes().forEach(v => {
      const node = g.node(v);
      nodeMap[v].x = node.x;
      nodeMap[v].y = node.y;
    });
    g.edges().forEach((e, i) => {
      const edge = g.edge(e);
      if (useEdgeControlPoint) {
        edges[i].controlPoints = edge.points.slice(1, edge.points.length - 1);
      }
    });
  }

上面是官方插件有向图的核心代码, 用到了dagre算法, 再简化一点其实可以理解为就是利用某种算法确定节点和边的位置.

最终执行布局的地方:

// g6/src/controller/layout.js
graph._executeLayout(processor, nodes, edges, groups)

Util插件

这类插件相对简单许多, 就是将函数内置到Util中. 最后直接在G6.Util中使用即可

比如一个生成模拟数据的:

// g6/plugins/util.randomData/index.js
const G6 = require('@antv/g6');
const Util = G6.Util;
const randomData = {
  // generate chain graph data
  createChainData(num) {
    const nodes = [];
    const edges = [];
    for (let index = 0; index < num; index++) {
      nodes.push({
        id: index
      });
    }
    nodes.forEach((node, index) => {
      const next = nodes[index + 1];
      if (next) {
        edges.push({
          source: node.id,
          target: next.id
        });
      }
    });
    return {
      nodes,
      edges
    };
  },
  // generate cyclic graph data
  createCyclicData(num) {
    const data = randomData.createChainData(num);
    const { nodes, edges } = data;
    const l = nodes.length;
    edges.push({
      source: data.nodes[l - 1].id,
      target: nodes[0].id
    });
    return data;
  },
  // generate num * num nodes without edges
  createNodesData(num) {
    const nodes = [];
    for (let index = 0; index < num * num; index++) {
      nodes.push({
        id: index
      });
    }
    return {
      nodes
    };
  }
};
Util.mix(Util, randomData);