Description infrastructure work

[zepumph]

At some point there will be space to add the larger improvements to a11y in scenery that we have been putting off for some time. It would be good to keep track of them in one place to get an idea of the scope of work and priority of different pieces.

Higher priority

• Cleanup from JO's review
• Fix a11y behavior functions (!!!!!)
• Implement a11y api for adding PDOM headings
• Prevent A11y events after focus changes
• Handling 'activation' events
• A11y performance optimizations

somewhere in the middle?

• Pickable should work with a11y listeners
• Add support for aria-activedescendant
• Better implementation for association attributes
• More abstraction for accessible components
• Consistency of scenery-internal code

Lower priority

• Audit PDOM structure of a screen after construction
• h3 allows both 'text' as inner content and has children
• Add more dag related tests for aria-labelledby associations

@jessegreenberg please edit inline any of these, as well as adding more that you have on you list.

It some of these may not need dedicated time, but I like the idea of having everything in the same place. I also think it may help @emily-phet understand the scope of infrastructure work that we are skating through/ignoring at the moment.

[emily-phet]

@zepumph Thanks! This is very helpful.

[zepumph]

@kathy-phet, I just found this issue. This seems to get at the heart of the description work that could be continued, much of this is based on @jonathanolson's review of PDOM work done back in 2018.