Allow preventing scroll when an element is focused

[krksgbr]

I've added a data-focus-preventScroll attribute to enable specifying elements that should not initiate scrolling when they receive focus.

I opted for this instead of dispatching a custom event that can be prevented, because it seemed simpler. What do you think?

[krksgbr]

Seems like cypress runs the test on an outdated version of webkit.
The preventScroll focus option has been supported for a while:

https://github.com/WebKit/WebKit/blame/68c99280815be0b90f3541350037619b33b0dd06/Source/WebCore/dom/FocusOptions.h#L45

I'm not sure if we can configure a newer webkit version.
A quick alternative would be to disable the test in webkit:

  if (Cypress.browser.name === 'webkit') {
    return
  }

https://docs.cypress.io/api/cypress-api/browser

[knuton]

The failing test says AssertionError: expected 0 to not equal 0, I think that implies that the browser does not scroll for the second test condition, where scrolling is expected?

[krksgbr]

The failing test says AssertionError: expected 0 to not equal 0, I think that implies that the browser does not scroll for the second test condition, where scrolling is expected?

In the meantime I've found out that in the case of webkit, the reported scrollX values are wrong. The tests run in an iframe, but cypress reports the scroll of the parent window. I'm exploring a workaround.

[knuton]

OK, let's go with this. It may be simpler than triggering an event.

Can you add to the README?

We could consider allowing to mark an entire subtree as no-scroll, but I am not sure that would be needed. We could expand to that if the need becomes apparent.

[knuton]

I would prefer sticking to kebab-case.

Suggested change

	const preventScroll = target.hasAttribute("data-focus-preventScroll")
	const preventScroll = target.hasAttribute("data-focus-prevent-scroll")