一、回顾

  contextPad就是元素追加的上下文,可以直接在画板上的元素上添加其他元素。

  在前面我们自定义了palette和render模块后，左侧工具栏和画板上的元素已经变成自定义的样式，但是contextPad这部分还没有变化。同样这里也需要重写contextPad的方法来覆盖默认方法。

二、文件结构

在plugins文件目录下新建context-pad文件夹。创建一个index.js入口文件和contextPadProvider.js自定义contextPad文件（用来覆盖默认contextPad）。

三、代码实现

1. contextPadProvider.js文件

import {
  assign,
  forEach,
  isArray
} from "min-dash";

import {
  is
} from "bpmn-js/lib/util/ModelUtil";

import {
  isAny
} from "bpmn-js/lib/features/modeling/util/ModelingUtil";

import {
  hasPrimaryModifier
} from "diagram-js/lib/util/Mouse";

export default function ContextPadProvider(
  config,
  injector,
  eventBus,
  contextPad,
  modeling,
  elementFactory,
  connect,
  create,
  popupMenu,
  canvas,
  rules,
  translate,
  elementRegistry
) {
  config = config || {};

  contextPad.registerProvider(this);

  this._contextPad = contextPad;
  this._modeling = modeling;
  this._elementFactory = elementFactory;
  this._connect = connect;
  this._create = create;
  this._popupMenu = popupMenu;
  this._canvas = canvas;
  this._rules = rules;
  this._translate = translate;

  if (config.autoPlace !== false) {
    this._autoPlace = injector.get("autoPlace", false);
  }

  eventBus.on("create.end", 250, function (event) {
    var context = event.context,
      shape = context.shape;

    if (!hasPrimaryModifier(event) || !contextPad.isOpen(shape)) {
      return;
    }

    var entries = contextPad.getEntries(shape);

    if (entries.replace) {
      entries.replace.action.click(event, shape);
    }
  });
}

ContextPadProvider.$inject = [
  "config.contextPad",
  "injector",
  "eventBus",
  "contextPad",
  "modeling",
  "elementFactory",
  "connect",
  "create",
  "popupMenu",
  "canvas",
  "rules",
  "translate",
  "elementRegistry"
];

ContextPadProvider.prototype.getContextPadEntries = function (element) {
  var contextPad = this._contextPad,
    modeling = this._modeling,
    elementFactory = this._elementFactory,
    connect = this._connect,
    create = this._create,
    popupMenu = this._popupMenu,
    canvas = this._canvas,
    rules = this._rules,
    autoPlace = this._autoPlace,
    translate = this._translate;

  var actions = {};

  if (element.type === "label") {
    return actions;
  }

  var businessObject = element.businessObject;

  function startConnect(event, element) {
    connect.start(event, element);
  }

  function removeElement() {
    modeling.removeElements([element]);
  }



  /**
   * Create an append action
   *
   * @param {string} type
   * @param {string} className
   * @param {string} [title]
   * @param {Object} [options]
   * @return {Object} descriptor
   */
  function appendAction(type, className, title, options) {
    if (typeof title !== "string") {
      options = title;
      title = translate("Append {type}", {
        type: type.replace(/^bpmn:/, "")
      });
    }

    function appendStart(event, element) {
      var shape = elementFactory.createShape(assign({
        type: type
      }, options));
      create.start(event, shape, {
        source: element
      });
    }

    var append = autoPlace ?
      function (event, element) {
        var shape = elementFactory.createShape(assign({
          type: type
        }, options));

        autoPlace.append(element, shape);
      } :
      appendStart;

    return {
      group: "model",
      className,
      title,
      action: {
        dragstart: appendStart,
        click: append
      }
    };
  }


  if (is(businessObject, "bpmn:FlowNode")) {

    if (
      !is(businessObject, "bpmn:EndEvent")
    ) {
      assign(actions, {
        "append.append-task": appendAction("bpmn:UserTask", "icon-custom taskNode", translate("Append Task")),
        "append.gateway": appendAction("bpmn:ExclusiveGateway", "icon-custom gatewayNode", translate("Append Gateway")),
        "append.end-event": appendAction("bpmn:EndEvent", "icon-custom endNode", translate("Append EndEvent")),
      });
    }
  }

  if (isAny(businessObject, ["bpmn:FlowNode", "bpmn:InteractionNode", "bpmn:DataObjectReference", "bpmn:DataStoreReference"])) {
    assign(actions, {

      connect: {
        group: "edit",
        // className: "bpmn-icon-connection-multi",
        className: "feelec feel-lianxian",
        title: translate("Connect using " + (businessObject.isForCompensation ? "" : "Sequence/MessageFlow or ") + "Association"),
        action: {
          click: startConnect,
          dragstart: startConnect
        }
      }
    });
  }



  // delete element entry, only show if allowed by rules
  var deleteAllowed = rules.allowed("elements.delete", {
    elements: [element]
  });

  if (isArray(deleteAllowed)) {
    // was the element returned as a deletion candidate?
    deleteAllowed = deleteAllowed[0] === element;
  }

  if (deleteAllowed) {
    assign(actions, {
      delete: {
        group: "edit",
        className: "bpmn-icon-trash",
        title: translate("Remove"),
        action: {
          click: removeElement
        }
      }
    });
  }
  return actions;
};

代码思路解析：

重写 ContextPadProvider 类，同时覆盖了其原型上的 getContextPadEntries 方法
getContextPadEntries 方法返回一个对象,和 PaletteProvider 一样，返回的是需要的元素。

不同的是 contextPad 通过判断元素的类型来决定追加哪些元素。比如在结束节点 EndEvent 就没有其他元素，只有一个删除节点，而其他节点一样，所以就需要在 EndEvent 这个节点单独判断。

2. inedx.js文件

import CustomContextPadProvider from "./contextPadProvider";

export default {
  __init__: ["contextPadProvider"],
  contextPadProvider: ["type", CustomContextPadProvider]
};

3.css文件

自定义样式文件process-panel.scss里再加入样式 contextPad 原生hover样式。

.djs-context-pad{
  & .startNode.entry:hover {
    background: url('../../../../../../public/bpmn_imgs/startNode.png') center no-repeat !important;
    background-size: cover !important;
  }
  & .endNode.entry:hover {
    background: url('../../../../../../public/bpmn_imgs/endNode.png') center no-repeat !important;
    background-size: cover !important;
  }
  & .taskNode.entry:hover {
    background: url('../../../../../../public/bpmn_imgs/taskNode.png') center no-repeat !important;
    background-size: cover !important;
  }
  & .gatewayNode.entry:hover {
    background: url('../../../../../../public/bpmn_imgs/gatewayNode.png') center no-repeat !important;
    background-size: cover !important;
  }
  & .entry {
    box-sizing: border-box;
    background-size: 100%;
    transition: all 0.3s;
  }
  & .entry:hover {
    border: 1px solid #1890ff;
  }
} 

四、整合使用

到这里需要自定义样式的这三部分就完成了，最后的使用就在初始化BpmnModeler时添加这三个自定义模块。
customBpmn.vue文件

<template>
  <div>
    <div ref="bpmn-canvas">
  </div>
</template>

<script>
import BpmnModeler from "bpmn-js/lib/Modeler";
// 自定义左侧菜单（修改 默认任务 为 用户任务）
import CustomPaletteProvider from "../package/process-designer/plugins/palette";
// 自定义渲染
import CustomRenderer from "../package/process-designer/plugins/render";
// 自定义元素选中时的弹出菜单（修改 默认任务 为 用户任务）
import CustomContextPadProvider from "../package/process-designer/plugins/context-pad";
export default {
  data() {
    return {
      bpmnModeler: null,
    };
  },
  mounted() {
    this.initBpmnModeler();
  },
  methods: {
    initBpmnModeler() {
      if (this.bpmnModeler) return;
      this.bpmnModeler = new BpmnModeler({
        container: this.$refs.bpmn - canvas,
        additionalModules: [
          CustomPaletteProvider,
          CustomRenderer,
          CustomContextPadProvider,
        ], //添加自定义模块
      });
    },
  },
};
</script>

五、效果展示

最后这三部分都变成自定义的样式了，要修改样式或者逻辑就在对应的文件修改，灰常Nice!!!