fix: keyboard navigation when using position fixed

[sissbruecker]

Description

Keyboard navigation for tab bar is currently broken when the element is within the app layout's drawer. The cause is the following check which incorrectly identifies all tabs as hidden:

web-components/packages/a11y-base/src/focus-utils.js

Lines 148 to 153 in 7a9fbf1

	// `offsetParent` is `null` when the element itself
	// or one of its ancestors is hidden with `display: none`.
	// https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/offsetParent
	if (element.offsetParent === null) {
	return true;
	}

The problem is that offsetParent is also null if the element is using fixed positioning. It can also be null for nested elements in a container with fixed positioning, such as for the tabs being in the app layouts drawer.

This change adds an additional check to verify that items have no client size which would be another indicator that display: none is being used in the hierarchy.

Fixes #5706

Type of change

• Bugfix

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[sissbruecker]

Also wanted to check the child's visibility here, but in case of these nested divs, the child's offset parent is actually the parent div. In case of tabs being used within the app layouts drawer there must be some additional detail that causes the offset parent to become null.