Allowed values of aria-autocomplete for the combobox role

I am working on issue 610, which involves writing a new description for the
combobox role -- something I have wanted to improve for a very long time!

 

There is one part of the current role description that I have never
understood. I believe it should be removed, but perhaps, just maybe, there
is a rational explaination for it. It is this text:

 

"If an author sets a combobox's value of aria-autocomplete to 'none'
(default), authors must manage and set focus on the associated listbox, so
assistive technologies can follow the currently selected value."

 

The part that does not make sense to me is the notion that a combobox could
ever have autocomplete set to none, especially if there are values in an
associated list that assistive technologies would need to track. The very
definition of autocomplete none is that there are no input completion
suggestions provided. Well then, what are the values in the list???

 

Since, by definition,  a combobox always has an associated list, it seems to
me that the allowed values of autocomplete should not include none, even if
the list is empty or collapsed.

 

My burning question is under what circumstances would it be appropriate to
set autocomplete to none on a combobox?

 

So far, the only rationale I have dreamed up is that autocomplete
dynamically changes based on whether the list is populated and displayed.
But, if it is not populated and not displayed, then there are no options for
the AT to track. Further, there would be no point in using aria-expanded if
aria-autocomplete is intended to serve this purpose.

 

A question almost as perplexing is under what conditions would autocomplete
inline be used instead of autocomplete both? If the value in the text field
is being completed inline from values displayed in a listbox, then
autocomplete should be set to both. Again, remember that by definition, a
combobox always has a list.

 

It seems to me that the allowed values for autocomplete on a combobox should
include only list and both. 

 

Thanks,

Matt King