@chandlerprall status of this PR and what I need help on:

1. Keydown events are handled in both data_grid.tsx and data_grid_cell. Preferably this could be on one place. My guess is that it could all be in data_grid_cell at this point.
2. data_grid_cell.tsx now has a popover in EuiDataGridCellContent. The state for this popover is managed in the two separate components in that file. Likely it should be done completely through pass downs.
3. Cell focus needs to reflect that state (of the popover) regardless of it being initiated through a keydown event or mouse event. On press, the popover should take focus. On close, the origin cell should take focus.
4. The popover content has an example of using schema to change the content. Likely we'd want one for each schema type, and my guess there is a better way to do that then managing it in that file. Likewise, we'll probably want a way for someone to override the popover content with a custom render.

Keydown events are handled in both data_grid.tsx and data_grid_cell. Preferably this could be on one place. My guess is that it could all be in data_grid_cell at this point.

I think the current distinction / placement makes sense: grid owns top-level arrow keys for navigation and escape for exiting full screen, while the cell-level keydown handler toggles the popover. There doesn't seem to be any conflict between the two handlers.

• Merged cell popover states together, refactored to be smaller and nicer.
• Cell focus has been cleaned up, focus is now returned when the popover closes.
• Popover content formatting has been refactored, added support for custom formatters to be passed in.

I think this is ready to take out of draft.

I have some screen reader work to do here (mostly announcing position and controls for the popup), but the rest of this PR is safe to review.

Going to wait until @snide has a chance to work on the SR support before reviewing. Let me know if you want a hand brainstorming UX or anything else.

Cell level accessibility / announcing is now in. The tab issue of not being able to tab out of the table will need to get fixed by @chandlerprall. My latest commit unfortunately breaks the tests, but they should be easy to fix. Just need a session with chandler to figure how to grep the inner content and ignore the new screenreader stuff.

Video here http://snid.es/c9148f9142c6

We still also need to fix tabbing throughout the cells. Do we want to do that in this PR or a follow up?

Also, I made a few tweaks:

• tabIndex={-1} to buttons that are set with aria-hidden="true" because things that aren't screen reader accessible shouldn't be navigated to by keyboard either (Explanation)
• removed a static ID from a subcomponent that DataGrid renders (wasn't being used and was causing axe to throw errors)
• moved popover boundary announcement/instructions to aria-describedby instead of aria-labelledby (labels should be reserved for titling content, descriptions will more typically hold special instructions)
• Removed all of the draggable ARIA/keyboard stuff off of the grab icon. This was duplicate functionality off of the row, had two tab stops within itself, and didn't have any focus states.

Thanks for the backup on the accessibility bits, especially the id gen. That would have been bad!

We still also need to fix tabbing throughout the cells. Do we want to do that in this PR or a follow up?

Plan was to do it in this one, since it broke in this one.

Yep, I'm working on the cell tabbing right now.

Changes to tab functionality have effectively been reverted. Tabbing to the table should focus the grid's focus cell, another tab should take you off the grid even if there are interactive elements in cells.

Changes to tab functionality have effectively been reverted

I'm still seeing the same tab behavior that I commented with earlier...

@thompsongl thanks for testing that... when I refactored the changes I failed to add it to expandable cells. Fixed

Bad merge, fixing.

For some reason I can't get this to merge correctly against feature/euidatagrid. I'm closing in in favor of #2418 which started a new branch to do the reverse and works fine. Will be merging on CI.