[Question] aria-rowcount and aria-rowindex vs. aria-setsize and aria-posinset for treegrid

[NeoDobby]

In the aria practices, it is specified that table, grid and treegrid must specify the aria-rowcount and aria-rowindex attributes if not all rows are in the DOM. But it is not completely clear how this should work within a treegrid.

Is the rowcount to include all rows in the table or just root-level rows? And related to that, is the rowindex supposed to be only the index within the list of top level rows, or all the rows?

• If all rows should be included, this would make it really difficult to handle in scenarios where child rows are only loaded when expanding, and it's impossible to find out what the total would be if all rows are expanded without requesting data about the children of each expandable item.
• If only top level rows are included, would this not already be covered by using aria-setsize and aria-posinset on all levels of the hierarchy?

So essentially, should rowcount and rowindex really be required for treegrid if setsize and posinset would be enough to appropriately define the tree hierarchy?

[mcking65]

@NeoDobby, these are really good questions. I don't think we've really thought this through.

It does seem like we have made aria-rowindex redundant with aria-posinset in treegrids. The spec says the following for aria-posinset:

If all items in a set are present in the document structure, it is not necessary to set this attribute, as the user agent can automatically calculate the set size and position for each item. However, if only a portion of the set is present in the document structure at a given moment, this property is needed to provide an explicit indication of an element's position.

The same redundancy also exists between aria-rowcount and aria-setsize.

I believe you should be safe using aria-posinset and aria-setsize in a treegrid and not using aria-rowindex and aria-rowcount. However, I will raise this for group discussion in an upcoming authoring practices meeting.

I have also raised it for discussion in the specification working group with w3c/aria#1303.

[NeoDobby]

Thank you, that helps!