fix(get-background-color): No longer calculate color from non-opaque overlapping element

[roman-bytes]

…overlapping elm

Prevents calculating color contrast ratio that have an overlapping element

Closes issue: #1459

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[AutoSponge]

I'm worried this will ignore overlays that cause a problem. Is it possible we can only apply this rule to contents contained by the intert attribute or aria-hidden? Also, if that's the case, maybe we don't have to do the calculation at all, just skip the color contrast check all together.

[straker]

Can you give an example of an overlay that causes a problem? One issue is that not all overlays are well written and inert or aria-hidden the rest of the page. Some will just focus trap (or not) the overlay without truly hiding everything else.

[AutoSponge]

I'd argue that an incomplete (incorrect) implementation should get the color-contrast rule as-is. If they add inert/aria-hidden to a container, those elements can be exempt from this rule. The overlay I'm referring to is the one in the linked issue. Without looking at the implementation, I would need to make sure that there are no tab stops in the overlaid section (inert) before I said that contrast doesn't matter.