Take you step by step to draw a flow chart using vue3.x

How to draw a flow chart using vue3.x? The following article will share with you the flow chart drawing method based on vue3.x. I hope it will be helpful to you!

##GitHub-workflow

https://github.com/554246839/component -test/tree/dev/src/components/workflow

This is mainly about flow chart drawing and implementation methods for workflow scenarios. (Learning video sharing:

vuejs video tutorial)

The following is the rendering:

Overall structural layout:

List of functions to be implemented:

Configurable configuration of nodes and connecting lines
• Drag-and-drop and rendering of nodes and drawing of connecting lines
• Selection of nodes and connecting lines
• Style adjustment of nodes
• Adsorption when moving nodes
• Undo and restore

Configurable nodes and connecting lines

Node configuration information

• [
    {
      'id': '', // 每次渲染会生成一个新的id
      'name': 'start', // 节点名称，也就是类型
      'label': '开始', // 左侧列表节点的名称
      'displayName': '开始', // 渲染节点的显示名称（可修改）
      'className': 'icon-circle start', // 节点在渲染时候的class，可用于自定义节点的样式
      'attr': { // 节点的属性
        'x': 0, // 节点相对于画布的 x 位置
        'y': 0, // 节点相对于画布的 y 位置
        'w': 70, // 节点的初始宽度
        'h': 70  // 节点的初始高度
      },
      'next': [], // 节点出度的线
      'props': [] // 节点可配置的业务属性
    },
    // ...
  ]

Connecting line configuration information

• // next
  [
    {
      // 连接线的id
      'id': 'ee1c5fa3-f822-40f1-98a1-f76db6a2362b',
      // 连接线的结束节点id
      'targetComponentId': 'fa7fbbfa-fc43-4ac8-8911-451d0098d0cb',
      // 连接线在起始节点的方向
      'directionStart': 'right',
      // 连接线在结束节点的方向
      'directionEnd': 'left',
      // 线的类型（直线、折线、曲线）
      'lineType': 'straight',
      // 显示在连接线中点的标识信息
      'extra': '',
      // 连接线在起始节点的id
      'componentId': 'fde2a040-3795-4443-a57b-af412d06c023'
    },
    // ...
  ]

Node attribute configuration structure

• // props
  [
    {
      // 表单的字段
      name: 'displayName',
      // 表单的标签
      label: '显示名称',
      // 字段的值
      value: '旅客运输',
      // 编辑的类型
      type: 'input',
      // 属性的必填字段
      required: true,
      // 表单组件的其它属性
      props: {
          placeholder: 'xxx'
      }
    },
    // ...
  ]

For the drop-down selected data, if there is a lot of drop-down data, the amount of data saved in the configuration will also be very large, so all the drop-down data can be Unified data management. When obtaining the information of the configuration node on the left, extract all the drop-down data and save it with the name value of props as the key. When using it, use props.name to get the corresponding drop-down data.

In addition, you need to configure the properties of the connecting line. Compared with the properties of the nodes, the properties of each node may be different, but the connecting line will not exist when there are no nodes, so we must prepare it first. The properties of the connection line are added to the properties of the connection line when the connection line is generated. Of course, we can set the properties of the connecting lines to be the same, or we can set the properties of different connecting lines according to different nodes.

The last method used:

<template>
  <workflow
    ref="workflowRef"
    @component-change="getActiveComponent"
    @line-change="getActiveLine"
    main-height="calc(100vh - 160px)">
  </workflow>
</template>


<script setup>
import { ref } from &#39;vue&#39;
import Workflow from &#39;@/components/workflow&#39;
import { commonRequest } from &#39;@/utils/common&#39;
import { ElMessage, ElMessageBox } from &#39;element-plus&#39;
import { useRoute } from &#39;vue-router&#39;

const route = useRoute()

const processId = route.query.processId // || &#39;testca08c433c34046e4bb2a8d3ce3ebc&#39;
const processType = route.query.processType

// 切换的当前节点
const getActiveComponent = (component: Record<string, any>) => {
  console.log(&#39;active component&#39;, component)
}

// 切换的当前连接线
const getActiveLine = (line: Record<string, any>) => {
  console.log(&#39;active line&#39;, line)
}

const workflowRef = ref<InstanceType<typeof Workflow>>()

// 获取配置的节点列表
const getConfig = () => {
  commonRequest(`/workflow/getWorkflowConfig?processType=${processType}`).then((res: Record<string, any>) => {
    // 需要把所有的属性根据name转换成 key - value 形式
    const props: Record<string, any> = {}
    transferOptions(res.result.nodes, props)
    // 设置左侧配置的节点数据
    workflowRef.value?.setConfig(res.result)
    getData(props)
  })
}
// 获取之前已经配置好的数据
const getData = (props: Record<string, any>) => {
  commonRequest(`/workflow/getWfProcess/${processId}`).then((res: Record<string, any>) => {
    // 调整属性，这里是为了当配置列表的节点或者属性有更新，从而更新已配置的节点的属性
    adjustProps(props, res.result.processJson)
    // 设置已配置好的数据，并渲染
    workflowRef.value?.setData(res.result.processJson, res.result.type || &#39;add&#39;)
  })
}

const init = () => {
  if (!processId) {
    ElMessageBox.alert(&#39;当前没有流程id&#39;)
    return
  }
  getConfig()
}
init()

const transferOptions = (nodes: Record<string, any>[], props: Record<string, any>) => {
  nodes?.forEach((node: Record<string, any>) => {
    props[node.name] = node.props
  })
}

const adjustProps = (props: Record<string, any>, nodes: Record<string, any>[]) => {
  nodes.forEach((node: Record<string, any>) => {
    const oldProp: Record<string, any>[] = node.props
    const res = transferKV(oldProp)
    node.props = JSON.parse(JSON.stringify(props[node.name]))
    node.props.forEach((prop: Record<string, any>) => {
      prop.value = res[prop.name]
    })
  })
}

const transferKV = (props: Record<string, any>[]) => {
  const res: Record<string, any> = {}
  props.forEach((prop: Record<string, any>) => {
    res[prop.name] = prop.value
  })
  return res
}
</script>

Drag and render the node and draw the connecting line

I won’t say much about the dragging of the node Yes, it is the usage related to drag, mainly the design of nodes and connecting lines in the rendering area.

The idea of ​​the rendering area here is: use the canvas element as the canvas background, the node is rendered in the form of a div, and the dragged position will be moved based on the relative position of the canvas, roughly The structure is as follows:

<template>
    <!-- 渲染区域的祖先元素 -->
    <div>
        <!-- canvas 画布，绝对于父级元素定位， inset: 0; -->
        <canvas></canvas>
        <!-- 节点列表渲染的父级元素，绝对于父级元素定位， inset: 0; -->
        <div>
            <!-- 节点1，绝对于父级元素定位 -->
            <div></div>
            <!-- 节点2，绝对于父级元素定位 -->
            <div></div>
            <!-- 节点3，绝对于父级元素定位 -->
            <div></div>
            <!-- 节点4，绝对于父级元素定位 -->
            <div></div>
        </div>
    </div>
</template>

The drawing of the connecting line is to find the position of the targetComponentId component based on the information in the next field, and then draw a line between two points on the canvas.

There are three types of links: straight line, polyline, curve

Straight line

The straight line is the simplest to draw, just connect two points. .

// 绘制直线
const drawStraightLine = (
  ctx: CanvasRenderingContext2D, 
  points: [number, number][], 
  highlight?: boolean
) => {
  ctx.beginPath()
  ctx.moveTo(points[0][0], points[0][1])
  ctx.lineTo(points[1][0], points[1][1])
  // 是否是当前选中的连接线，当前连接线高亮
  shadowLine(ctx, highlight)
  ctx.stroke()
  ctx.restore()
  ctx.closePath()
}

Polyline

The polyline method is more complicated, because the polyline needs to avoid overlapping the connecting lines and nodes as much as possible, so It needs to determine the scenario of each connection line, and the width and height of the two nodes also need to be considered and calculated. As follows:

The starting node has four directions, the target node also has four directions, and the target node has four quadrants relative to the starting node, so strictly speaking , there are 4 * 4 * 4 = 64 scenarios in total. The polyline points in these scenes are also different. The maximum is 4 times and the minimum is 0 times. It takes 700 lines of code to find these 64 coordinate points alone.

The final drawing method is the same as the straight line:

// 绘制折线
const drawBrokenLine = ({ ctx, points }: WF.DrawLineType, highlight?: boolean) => {
  ctx.beginPath()
  ctx.moveTo(points[0][0], points[0][1])
  for (let i = 1; i < points.length; i++) {
    ctx.lineTo(points[i][0], points[i][1])
  }
  shadowLine(ctx, highlight)
  ctx.stroke()
  ctx.restore()
  ctx.closePath()
}

Curve

Compared with the polyline, the curve The idea will be much simpler, and there is no need to consider so many scenarios of polyline.

The polyline here is drawn using a third-order Bezier curve. Four fixed points are taken, two start and end points, and two control points, two of which are fixed. The starting and ending points are fixed, we only need to find the coordinates of the two control points. There is not much code here, so you can post it directly:

/**
 * Description: 计算三阶贝塞尔曲线的坐标
 */
import WF from '../type'

const coeff = 0.5
export default function calcBezierPoints({ startDire, startx, starty, destDire, destx, desty }: WF.CalcBezierType,
  points: [number, number][]) {

  const p = Math.max(Math.abs(destx - startx), Math.abs(desty - starty)) * coeff
  switch (startDire) {
    case 'down':
      points.push([startx, starty + p])
      break
    case 'up':
      points.push([startx, starty - p])
      break
    case 'left':
      points.push([startx - p, starty])
      break
    case 'right':
      points.push([startx + p, starty])
      break
    // no default
  }
  switch (destDire) {
    case 'down':
      points.push([destx, desty + p])
      break
    case 'up':
      points.push([destx, desty - p])
      break
    case 'left':
      points.push([destx - p, desty])
      break
    case 'right':
      points.push([destx + p, desty])
      break
    // no default
  }
}

To put it simply, the first control point is calculated based on the starting point, and the second control point is calculated based on the ending point. The calculation method is to continue to calculate a distance based on the direction of the current point relative to the node, and this distance is based on half of the maximum relative distance between the starting and ending points (it may be a bit roundabout...).

Drawing method:

// 绘制贝塞尔曲线
const drawBezier = ({ ctx, points }: WF.DrawLineType, highlight?: boolean) => {
  ctx.beginPath()
  ctx.moveTo(points[0][0], points[0][1])
  ctx.bezierCurveTo(
    points[1][0], points[1][1], points[2][0], points[2][1], points[3][0], points[3][1]
  )
  shadowLine(ctx, highlight)
  ctx.stroke()
  ctx.restore()
  ctx.globalCompositeOperation = 'source-over'    //目标图像上显示源图像
}

节点与连接线的选择

节点是用 div 来渲染的，所以节点的选择可以忽略，然后就是连接点的选择，首先第一点是鼠标在移动的时候都要判断鼠标的当前位置下面是否有连接线，所以这里就有 3 种判断方法，呃... 严格来说是两种，因为折线是多条直线，所以是按直线的判断方法来。

// 判断当前鼠标位置是否有线
export const isAboveLine = (offsetX: number, offsetY: number, points: WF.LineInfo[]) => {
  for (let i = points.length - 1; i >= 0; --i) {
    const innerPonints = points[i].points
    let pre: [number, number], cur: [number, number]
    // 非曲线判断方法
    if (points[i].type !== 'bezier') {
      for (let j = 1; j < innerPonints.length; j++) {
        pre = innerPonints[j - 1]
        cur = innerPonints[j]
        if (getDistance([offsetX, offsetY], pre, cur) < 20) {
          return points[i]
        }
      }
    } else {
      // 先用 x 求出对应的 t，用 t 求相应位置的 y，再比较得出的 y 与 offsetY 之间的差值
      const tsx = getBezierT(innerPonints[0][0], innerPonints[1][0], innerPonints[2][0], innerPonints[3][0], offsetX)
      for (let x = 0; x < 3; x++) {
        if (tsx[x] <= 1 && tsx[x] >= 0) {
          const ny = getThreeBezierPoint(tsx[x], innerPonints[0], innerPonints[1], innerPonints[2], innerPonints[3])
          if (Math.abs(ny[1] - offsetY) < 8) {
            return points[i]
          }
        }
      }
      // 如果上述没有结果，则用 y 求出对应的 t，再用 t 求出对应的 x，与 offsetX 进行匹配
      const tsy = getBezierT(innerPonints[0][1], innerPonints[1][1], innerPonints[2][1], innerPonints[3][1], offsetY)
      for (let y = 0; y < 3; y++) {
        if (tsy[y] <= 1 && tsy[y] >= 0) {
          const nx = getThreeBezierPoint(tsy[y], innerPonints[0], innerPonints[1], innerPonints[2], innerPonints[3])
          if (Math.abs(nx[0] - offsetX) < 8) {
            return points[i]
          }
        }
      }
    }
  }

  return false
}

直线的判断方法是点到线段的距离：

/**
 * 求点到线段的距离
 * @param {number} pt 直线外的点
 * @param {number} p 直线内的点1
 * @param {number} q 直线内的点2
 * @returns {number} 距离
 */
function getDistance(pt: [number, number], p: [number, number], q: [number, number]) {
  const pqx = q[0] - p[0]
  const pqy = q[1] - p[1]
  let dx = pt[0] - p[0]
  let dy = pt[1] - p[1]
  const d = pqx * pqx + pqy * pqy   // qp线段长度的平方
  let t = pqx * dx + pqy * dy     // p pt向量 点积 pq 向量（p相当于A点，q相当于B点，pt相当于P点）
  if (d > 0) {  // 除数不能为0; 如果为零 t应该也为零。下面计算结果仍然成立。                   
    t /= d      // 此时t 相当于 上述推导中的 r。
  }
  if (t < 0) {  // 当t（r）< 0时，最短距离即为 pt点 和 p点（A点和P点）之间的距离。
    t = 0
  } else if (t > 1) { // 当t（r）> 1时，最短距离即为 pt点 和 q点（B点和P点）之间的距离。
    t = 1
  }

  // t = 0，计算 pt点 和 p点的距离; t = 1, 计算 pt点 和 q点 的距离; 否则计算 pt点 和 投影点 的距离。
  dx = p[0] + t * pqx - pt[0]
  dy = p[1] + t * pqy - pt[1]

  return dx * dx + dy * dy
}

关于曲线的判断方法比较复杂，这里就不多介绍， 想了解的可以去看这篇：如何判断一个坐标点是否在三阶贝塞尔曲线附近

连接线还有一个功能就是双击连接线后可以编辑这条连接线的备注信息。这个备注信息的位置是在当前连接线的中心点位置。所以我们需要求出中心点，这个相对简单。

// 获取一条直线的中点坐标
const getStraightLineCenterPoint = ([[x1, y1], [x2, y2]]: [number, number][]): [number, number] => {
  return [(x1 + x2) / 2, (y1 + y2) / 2]
}

// 获取一条折线的中点坐标
const getBrokenCenterPoint = (points: [number, number][]): [number, number] => {
  const lineDistancehalf = getLineDistance(points) >> 1

  let distanceSum = 0, pre = 0, tp: [number, number][] = [], distance = 0

  for (let i = 1; i < points.length; i++) {
    pre = getTwoPointDistance(points[i - 1], points[i])
    if (distanceSum + pre > lineDistancehalf) {
      tp = [points[i - 1], points[i]]
      distance = lineDistancehalf - distanceSum
      break
    }
    distanceSum += pre
  }

  if (!tp.length) {
    return [0, 0]
  }

  let x = tp[0][0], y = tp[0][1]

  if (tp[0][0] === tp[1][0]) {
    if (tp[0][1] > tp[1][1]) {
      y -= distance
    } else {
      y += distance
    }
  } else {
    if (tp[0][0] > tp[1][0]) {
      x -= distance
    } else {
      x += distance
    }
  }

  return [x, y]
}

曲线的中心点位置，可以直接拿三阶贝塞尔曲线公式求出

// 获取三阶贝塞尔曲线的中点坐标
const getBezierCenterPoint = (points: [number, number][]) => {
  return getThreeBezierPoint(
    0.5, points[0], points[1], points[2], points[3]
  )
}

/**
 * @desc 获取三阶贝塞尔曲线的线上坐标
 * @param {number} t 当前百分比
 * @param {Array} p1 起点坐标
 * @param {Array} p2 终点坐标
 * @param {Array} cp1 控制点1
 * @param {Array} cp2 控制点2
 */
export const getThreeBezierPoint = (
  t: number,
  p1: [number, number],
  cp1: [number, number],
  cp2: [number, number],
  p2: [number, number]
): [number, number] => {
  const [x1, y1] = p1
  const [x2, y2] = p2
  const [cx1, cy1] = cp1
  const [cx2, cy2] = cp2
  const x =
    x1 * (1 - t) * (1 - t) * (1 - t) +
    3 * cx1 * t * (1 - t) * (1 - t) +
    3 * cx2 * t * t * (1 - t) +
    x2 * t * t * t
  const y =
    y1 * (1 - t) * (1 - t) * (1 - t) +
    3 * cy1 * t * (1 - t) * (1 - t) +
    3 * cy2 * t * t * (1 - t) +
    y2 * t * t * t
  return [x | 0, y | 0]
}

在算出每一条的中心点位置后，在目标位置添加备注信息即可：

节点的样式调整

节点的样式调整主要是位置及大小，而这些属性就是节点里面的 attr，在相应的事件下根据鼠标移动的方向及位置，来调整节点的样式。

还有批量操作也是同样，不过批量操作是要先计算出哪些节点的范围。

// 获取范围选中内的组件
export const getSelectedComponent = (componentList: WF.ComponentType[], areaPosi: WF.Attr) => {
  let selectedArea: WF.Attr | null = null
  let minx = Infinity, miny = Infinity, maxx = -Infinity, maxy = -Infinity
  const selectedComponents = componentList.filter((component: WF.ComponentType) => {

    const res = areaPosi.x <= component.attr.x &&
      areaPosi.y <= component.attr.y &&
      areaPosi.x + areaPosi.w >= component.attr.x + component.attr.w &&
      areaPosi.y + areaPosi.h >= component.attr.y + component.attr.h

    if (res) {
      minx = Math.min(minx, component.attr.x)
      miny = Math.min(miny, component.attr.y)
      maxx = Math.max(maxx, component.attr.x + component.attr.w)
      maxy = Math.max(maxy, component.attr.y + component.attr.h)
    }
    return res
  })

  if (selectedComponents.length) {
    selectedArea = {
      x: minx,
      y: miny,
      w: maxx - minx,
      h: maxy - miny
    }
    return {
      selectedArea, selectedComponents
    }
  }
  return null
}

这个有个小功能没有做，就是在批量调整大小的时候，节点间的相对距离应该是不动的，这里忽略了。

节点移动时的吸附

这里的吸附功能其实是做了一个简单版的，就是 x 和 y 轴都只有一条校准线，且校准的优先级是从左至右，从上至下。

这里吸附的标准是节点的 6 个点：X 轴的左中右，Y 轴的上中下，当前节点在移动的时候，会用当前节点的 6 个点，一一去与其它节点的 6 个点做比较，在误差正负 2px 的情况，自动更新为0，即自定对齐。

因为移动当前节点时候，其它的节点是不动的，所以这里是做了一步预处理，即在鼠标按下去的时候，把其它的节点的 6 个点都线算出来，用 Set 结构保存，在移动的过程的比较中，计算量会相对较少。

// 计算其它节点的所有点位置
export const clearupPostions = (componentList: WF.ComponentType[], currId: string) => {
  // x 坐标集合
  const coordx = new Set<number>()
  // y 坐标集合
  const coordy = new Set<number>()

  componentList.forEach((component: WF.ComponentType) => {
    if (component.id === currId) {
      return
    }
    const { x, y, w, h } = component.attr
    coordx.add(x)
    coordx.add(x + (w >> 1))
    coordx.add(x + w)
    coordy.add(y)
    coordy.add(y + (h >> 1))
    coordy.add(y + h)
  })

  return [coordx, coordy]
}

判读是否有可吸附的点

// 可吸附范围
const ADSORBRANGE = 2
// 查询是否有可吸附坐标
const hasAdsorbable = (
  coords: Set<number>[], x: number, y: number, w: number, h: number
) => {
  // x, y, w, h, w/2, h/2
  const coord: (number | null)[] = [null, null, null, null, null, null]
  // 查询 x 坐标
  for (let i = 0; i <= ADSORBRANGE; i++) {
    if (coords[0].has(x + i)) {
      coord[0] = i
      break
    }
    if (coords[0].has(x - i)) {
      coord[0] = -i
      break
    }
  }

  // 查询 y 坐标
  for (let i = 0; i <= ADSORBRANGE; i++) {
    if (coords[1].has(y + i)) {
      coord[1] = i
      break
    }
    if (coords[1].has(y - i)) {
      coord[1] = -i
      break
    }
  }

  // 查询 x + w 坐标
  for (let i = 0; i <= ADSORBRANGE; i++) {
    if (coords[0].has(x + w + i)) {
      coord[2] = i
      break
    }
    if (coords[0].has(x + w - i)) {
      coord[2] = -i
      break
    }
  }

  // 查询 y + h 坐标
  for (let i = 0; i <= ADSORBRANGE; i++) {
    if (coords[1].has(y + h + i)) {
      coord[3] = i
      break
    }
    if (coords[1].has(y + h - i)) {
      coord[3] = -i
      break
    }
  }

  // 查询 x + w/2 坐标
  for (let i = 0; i <= ADSORBRANGE; i++) {
    if (coords[0].has(x + (w >> 1) + i)) {
      coord[4] = i
      break
    }
    if (coords[0].has(x + (w >> 1) - i)) {
      coord[4] = -i
      break
    }
  }

  // 查询 y + h/2 坐标
  for (let i = 0; i <= ADSORBRANGE; i++) {
    if (coords[1].has(y + (h >> 1) + i)) {
      coord[5] = i
      break
    }
    if (coords[1].has(y + (h >> 1) - i)) {
      coord[5] = -i
      break
    }
  }

  return coord
}

最后更新状态。

// 获取修正后的 x, y，还有吸附线的状态
export const getAdsordXY = (
  coords: Set<number>[], x: number, y: number, w: number, h: number
) => {
  const vals = hasAdsorbable(
    coords, x, y, w, h
  )

  let linex = null
  let liney = null

  if (vals[0] !== null) { // x
    x += vals[0]
    linex = x
  } else if (vals[2] !== null) { // x + w
    x += vals[2]
    linex = x + w
  } else if (vals[4] !== null) { // x + w/2
    x += vals[4]
    linex = x + (w >> 1)
  }

  if (vals[1] !== null) { // y
    y += vals[1]
    liney = y
  } else if (vals[3] !== null) { // y + h
    y += vals[3]
    liney = y + h
  } else if (vals[5] !== null) { // y + h/2
    y += vals[5]
    liney = y + (h >> 1)
  }

  return {
    x, y, linex, liney
  }
}

撤销和恢复

撤销和恢复的功能是比较简单的，其实就是用栈来保存每一次需要保存的配置结构，就是要考虑哪些操作是可以撤销和恢复的，就是像节点移动，节点的新增和删除，连接线的连接，连接线的备注新增和编辑等等，在相关的操作下面入栈即可。

// 撤销和恢复操作
const cacheComponentList = ref<WF.ComponentType[][]>([])
const currentComponentIndex = ref(-1)
// 撤销
const undo = () => {
  componentRenderList.value = JSON.parse(JSON.stringify(cacheComponentList.value[--currentComponentIndex.value]))
  // 更新视图
  updateCanvas(true)
  cancelSelected()
}
// 恢复
const redo = () => {
  componentRenderList.value = JSON.parse(JSON.stringify(cacheComponentList.value[++currentComponentIndex.value]))
  // 更新视图
  updateCanvas(true)
  cancelSelected()
}
// 缓存入栈
const chacheStack = () => {
  if (cacheComponentList.value.length - 1 > currentComponentIndex.value) {
    cacheComponentList.value.length = currentComponentIndex.value + 1
  }
  cacheComponentList.value.push(JSON.parse(JSON.stringify(componentRenderList.value)))
  currentComponentIndex.value++
}

最后

这里主要的已经差不多都写了，其实最红还有一个挺有用的功能还没有做。就是改变已经绘制的连接线的起止点。

这里的思路是：先选中需要改变起止点的连接线，然后把鼠标移动到起止点的位置，将它从已经绘制的状态改为正在绘制的状态，然后再选择它的开始位置或者结束位置。这个后面看情况吧，有空就加上。

（学习视频分享：web前端开发、编程基础视频）

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