[menu] Explicitly mention whether reading-flow should impact arrow key navigation

[lukewarlow]

Similar to a question I had about customisable select and reading-flow, per whatwg/html#10407 (comment) it seems that reading flow should impact the arrow key navigation of select options which is great. I'm assuming the same applies to the menu proposal. It would be good to explicitly state that in the proposal.

While it might not be best practice to randomly re-order things I think it would still be good if the keyboard accessibility is maintained in such scenarios.

Reading-flow isn't a complete situation (for example if you render your menu horizontally rather than vertically side arrows won't work but that can be dealt with in future.

[scottaohara]

Tbh, i would be concerned if someone was adjusting the reading flow of menus or selects. Moving keyboard focus will be the predominant method of navigation for these if they’re built properly.

I guess with select now being more permissive and people being able to easily mess that expected experience up by putting whatever the hell into their popups, maybe I shouldn’t expect that anymore…. But if built to pass validation / expected behaviors for these components, then it shouldn’t be too much of a concern. Sigh. guess we will have to see what people end up doing…