The Web Content Accessibility Guidelines version 2.1 added a success
criterion called Non-text Contrast [1], which mentions that the focus
indicator must contrast with the background, and version 2.2 introduced
a specific one regarding focus appearance [2]. According to that
criterion, the focus indicator:
* is at least as large as the area of a 2 CSS pixel thick perimeter of
the unfocused component or sub-component
* has a contrast ratio of at least 3:1 between the same pixels in the
focused and unfocused states.
Our current solution for highlighting elements on focus has a couple of
issues:
* It doesn't offer enough contrast against the default white background
(1.6:1)
* It offers even less contrast against other backgrounds, like the
homepage banner or the featured proposals/debates
Making the color of the outline darker would increase the contrast
against these backgrounds, but it would reduce the contrast against
other backgrounds like our default brand color.
For this reason, most modern browsers use a special double outline with
two different colors [3], and we're choosing to combine an outline and a
box shadow to emulate it, using the brand color as the second color.
However, this double-colored outline doesn't work so well when focusing
on dark buttons surrounded by a light background, so instead we're using
a triple outline, which works well on any color combination [4]. Since I
feel that making the third outline 2px wide makes the overall outline
too wide, I'm making the inner outline just 1px wide since that's enough
to prevent edge cases.
Note that Foundation adds a transition for the `box-shadow` property on
`select` controls, which gets in the way of the focus we use on the
language selector. So we're removing the transition.
Also note that the box-shadow style didn't work properly with the
box-shadow we added on the `:hover` status on cards, so we're changing
the code in order to cover this case.
Finally, note that the box-shadow isn't displayed properly on multiline
links (in Chrome, not even with `box-decoration-break: clone`), like the
ones in debates/proposals/polls/investments/processes titles, so we're
changing the style of these links to `inline-block`.
[1] https://www.w3.org/TR/WCAG21/#non-text-contrast
[2] https://www.w3.org/TR/WCAG22/#focus-appearance
[3] https://www.sarasoueidan.com/blog/focus-indicators/#examining-(current)-browser-focus-indicators-against-wcag-requirements
[4] https://www.erikkroes.nl/blog/the-universal-focus-state/
Captions benefit blind screen reader users who navigate through tables,
particularly in this case because we potentially have several tables
with headings (one table per group), so when navigating through tables
it might be hard to know which group the headings belong to.
In this case they also benefit sighted users. Usability tests have shown
the "Groups and headings" section is a bit confusing, so adding a
caption like "Headings in Districts" helps clarifying Districts is a
group and the table refers to headings in that group.
The very same table is rendered in the "headings" step of the budget
creation wizard. However, in that case the information of the caption is
redundant because the page is specific for headings belonging to a
certain group. We're making the element invisible but still keeping it
for screen reader users in order to ease their navigation through
tables.
