Combobox multi-select improvements

[gretanausedaite]

Combobox multi-select functionality has some concerns that could be improved:

• researched the accessibility concerns that come with this markup
• fix focus when multi-select is enabled
  • Scroll to one of the selected items on menu open
• test performance - we have some foreach loops that could cause problems with bigger datasets

[mayank99]

Adding some comments here as I've been working a lot with ComboBox multiselect lately.

In response to the original issue:

• Accessibility of multi-select has been improved in use live region for multiselect announcements #1228, and it also unblocks these two related issues:
  • Option to customize the display of selected items within ComboBox #894
  • Select: improve multi selected removal #907
• Focus still needs to be fixed. :(
• Performance seems to be ok? Haven't seen any user complaints so far, and virtualization is available too.

One new issue I noticed: after typing in a combobox and selecting an option (using Enter), I would have expected the text field to be cleared but it doesn't.

Also, when testing combobox in VO/NVDA (in general, not just multiselect), I was noticing weird behaviors and having some difficulty opening the menu. Will need to test and research some more. It might be better UX if we add inline autocomplete (#862).