feat(datepicker): make widget accessible

[bekos]

Tests and some polishing is missing, but I think this is one of the most accessible datepicker's out there! 👯

Added:

• Keyboard navigation in calendar and Escape on popup.
• Focus handling when closing/open popup.
• WAI-ARIA roles

Breaking changes:

• Looping modes is removed. Ie from max mode you don't move to min mode.
• For popup, open on focus is removed, but open with down arrow is added.

[bekos]

I am done with this! Anyone cares to review/test (and with a screen reader if possible) before merging ?

[jbthoma]

@bekos I think "open on focus" is far more standard practice than "open with down arrow". I can't think of a single site (that I've been to anyway) that requires a user to do that. Could you bring it back as an option at least? I'd even say it should be the default option, and the down arrow should come second.

[bekos]

@jbthoma Indeed, "open on focus" is a very common practice, but from my research this has accessibility issues. So I decided to remove from the core of the library. The "open on down arrow" it is an undocumented hack :-) / convenience I introduced and will probably remove also.

But you can still use this functionality by using is-open="dt.open" and ng-focus/ng-click = "dt.open = true", but I wouldn't like to put in the demo page. Let people copy the demo example and try to make a better world :-)

Just for reference, this is the accessibility example of datepicker: http://oaa-accessibility.org/examplep/datepicker1/

[temporafugiunt]

Bravo on these changes, I had some major usability issues like discussed in #1942 and #1880 when using the calendar in a data grid like scenario. The calendar is now much more usable and doesn't interrupt workflow. Awesome Job!

[rvanbaalen]

Even though this is topic pretty old I completely agree with @jbthoma regarding the open on focus. I just spent a little while figuring out what I did wrong because the popup didn't open on focus, which I expected.

I appreciate your efforts for accessibility but you should also keep usability in mind. Opening on focus as default and setting and having the arrow down option as extra / fallback would be way better imho. It's best of both worlds.