tree type series set roam as true cause the root node disapear in sight

[peter-wang-wsl]

Version

4.2.1

Steps to reproduce

1、add roam:true to option of https://echarts.baidu.com/examples/editor.html?c=tree-basic
2、click util node
3、click math node
4、click flare

What is expected?

display only flare node in original position

What is actually happening?

chart disapper

[echarts-bot]

Hi! We've received your issue and please be patient to get responded. 🎉
The average response time is expected to be within one day for weekdays.

In the meanwhile, please make sure that you have posted enough image to demo your request. You may also check out the API and chart option to get the answer.

Have a nice day! 🍵

[yufeng04]

According to the reproducing steps:

1. add roam:true to option
   
2. click 'util' and 'math' node
   
3. click 'flare'
   
   The root node didn't disapear in sight.

[peter-wang-wsl]

@yufeng04 you need click run to update your change, i can reproduce with chrome and fire fox

[sicraf]

作者的步骤并不能很好的重现这个bug，请参考以下步骤：
1、添加roam:true
2、拖动树


3、点击flare

整个树消失了

[yufeng04]

The reason lies in the function _updateViewCoordSys;
When we click flare, the number of points and the running result of function fromPoints will changes. So the value of defaultCenter will also change.
The the value of viewCoordSys.position is wrong, so the root node disappear in sight