Generalize the a11y view to work in other contexts

[jessegreenberg]

The a11y view makes assumptions about its context so that it can hook into a sim. @brettfiedler said that there was a POSE interest in generalizing it so that it could be used for things that are not PhET simulations.

@brettfiedler @jonathanolson FYI.

[marlitas]

@samreid We discussed this during the description/voicing roadmap meeting, and it came up that this might be a useful topic for Google Summer of Code. As well as any other outside contribution partnership.

[samreid]

@brettfiedler or @jessegreenberg can you please provide more context and direction here so the scope and proposal is more fully specified?

[jessegreenberg]

Scenery supports accessibility by creating an invisible HTML subtree that can be found with assistive technology. PhET created an "a11y view" to display that content for development and demo purposes. The a11y view and its implementation are specific to PhET simulations. It may be more useful to others if it could be used with other SceneryStack applications too.

The a11y view gets information from PhET simulation specific globals and tooling. To be used for other contexts, that needs to be removed or generalized.

In a quick scan I found the following things that might need to change:

• Variables like {{PHET_SIM_TITLE}} and {{PHET_SIM_URL}} need to be removed/replaced. We would need a way to generate the a11y view without that information.
• Remove/replace usages of phet.sim.joist and other simulation specific globals.
• Replace the way the filename is constructed for the iframe.
• The a11y view has code specific to built PhET simulations so it can run on phet-server, that should be removed.

And then any other features or improvements that would make it more useful as a general tool. Some ideas about design improvements are in #1510.

Maybe we would support an a11y view system in scenery, and make it extensible so that these PhET specific things could be added for our use.

The template and most of the implementation lives in chipper, called sim-a11y-view.html. Other related files are generateA11yViewHTML.ts and getA11yViewHTMLFromTemplate.