<issue_start><issue_comment>Title: 连接线起始点、终止点的位置坐标问题
username_0: <!--- Provide a general summary of the issue in the Title above. -->

### Expected Behavior
连接线起始点、终止点的位置问题
<!--- What should happen. -->

### Current Behavior

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### Possible Solution

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### Steps To Reproduce
strokeWidth = ‘1’ 终点坐标的是链接桩圆心位置
strokeWidth = ‘10’ 为什么终点坐标偏离链接桩圆心坐标？是否有问题？
strokeWidth = ‘50’ 偏离的更远了 。

目前使用的strokeWidth =‘4’ 导致连接线看上去没有连接到图形
![image](https://user-images.githubusercontent.com/22650893/135380997-26ff47e9-7f48-4dbd-b424-32492ac4575c.png)

![image](https://user-images.githubusercontent.com/22650893/135381652-9f722ca1-21d9-429e-8ad5-bc8562e469db.png)

![image](https://user-images.githubusercontent.com/22650893/135382045-7842ecd8-9a13-436e-a22f-7d617be22721.png)


### Additional Context

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### Your Environment

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-@antv/x6: [1.26.2]
<issue_comment>username_1: 连线宽度修改，相应的箭头的 `size` 也需要修改：
```ts
graph.addEdge({
  source: [50, 50],
  target: {
    cell: source,
    port: '1'
  },
  attrs: {
    line: {
      strokeWidth: 30,
      targetMarker: {
        name: 'block',
        size: 30,
        offset: 0,
      }
    }
  }
})
```<issue_closed>