Override scrollToIndex(number) in TreeGrid

[sosa-vaadin]

Describe your motivation

TreeGrid inherits the scrollToIndex(int) method from Grid but some complications arise from this. The complete structure of the Grid is needed to properly calculate how to scroll to an item using its index. One example is a node at index 3 with 5 children is expanded, the following node (previously at index 4) would move to index 9. When collapsed, the node at index 9 would move back to index 4.

Describe the solution you'd like

We need to provide a reliable method that can consistently scroll to any item using its index. The tree should be traversed in a pre-order traversal manner.

Describe alternatives you've considered

Making it possible to only scroll to root nodes. I'm not sure if this solution would work if any node is expanded since we would probably face the previous issue of having a node's index change when previous nodes are expanded or collapsed.

[sirbris]

Any updates on this?

[yuriy-fix]

We need to implement the Flow counterpart of the logic introduced in the web-components with vaadin/web-components#5428. We would like to keep the existing API, so we should have two methods available:

public void scrollToIndex(int rowIndex)
public void scrollToIndex(int... indexes)

[tomivirkki]

Also

• Update the implementation of scrollToEnd as advised here
• Add API for scrolling to a hierarchical index to the TreeGridElement (TB)
• Re-enable the tests annotated with @Ignore("Fix as part of https://github.com/vaadin/flow-components/issues/3505")