merge multiple isHidden utility functions

[jeeyyy]

We have multiple fn's that do more or less the same thing:

• dom.isVisible
• util.isHidden
• dom.isHiddenWithCss

Nice to have:

• It would be nice to merge these with optional arguments perhaps

Good to solve:

• see feat: Improve perf of axe.run [WWD-1821] #1503 (comment)

Must do:

• decorate @deprecated if we choose to not use any.

[straker]

Here's my findings in comparing the 3 functions

	utils/is-hidden	dom/is-visible	dom/is-hidden-with-css
takes single element	✓ Yes	✓ Yes	✓ Yes
takes screenReader option	× No	✓ Yes	× No
looks at nodeType	✓ Yes	✓ Yes	✓ Yes
looks at nodeName	× No	✓ Yes	✓ Yes
looks at css display	✓ Yes	✓ Yes	✓ Yes
looks at css visibility	✓ Yes	✓ Yes	✓ Yes
looks at aria-hidden	✓ Yes	✓ Yes	× No
looks at css clip	× No	✓ Yes	× No
looks at css opacity	× No	✓ Yes	× No
looks at css scroll height	× No	✓ Yes	× No
looks at offscreen	× No	✓ Yes	× No
recurses with parent el	✓ Yes	✓ Yes	✓ Yes

And how they are used in the code:

• utils/is-hidden
  • when gathering nodes in core/rule.js gather step
  • when gathering frames in core/context.js
• dom/is-hidden-with-css
  • checking if element is hidden in dom/focus-disabled.js
  • checking if form control is hidden in text/form-control-value.js
• dom/is-visible
  • everywhere else

utils/is-hidden is used only in the two files to gather nodes before passing them to a rule/check, and dom/is-hidden-with-css is used in two specific files, though I'm not sure why it is used over dom/is-visible. dom/is-visible is used the majority of the time (59 matches when doing a search) and is the function other code bases use to check an elements visibility.

Therefore, I propose we deprecate utils/is-hidden and dom/is-hidden-with-css and use dom/is-visible as the single function. Since we need the function in core, we can move the function to utils and export it in dom like we've done for other functions (making it backwards compatible). The function covers everything the other two functions does, and more, so we should be able to make it work for all use cases.

[straker]

@WilcoFiers suggest mimicking ACT definitions of is-visible and is-hidden-state which help distinguish when a DOM node is visually visible (offscreen, visible, etc., excluding aria-hidden) and when a node is hidden from the accessibility tree (looks at aria-hidden, visibility, and display)

[WilcoFiers]

I don't see us ever making this change. I don't think the effort out weights the effort involved in making this change.