framework/less/common/mixins/accessibility.less
David Wheatley 8a431dc3cc
[A11Y] Add focus ring mixin to restore ring to elements which no longer have it (#2814)
* Add focus ring mixin

These mixins allow us to restore default browser focus rings on elements which no longer have them.

* Add info about custom outline styles; use `#private` namespace and fix mixin name

I just learned that Less has namespaces! https://lesscss.org/features/#mixins-feature-namespaces
2021-04-29 22:10:17 +01:00

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// This mixin should **only** be used in this file. If you want to define your own
// custom outline style(s), override this mixin in your own theme extension, or in
// the Custom Less section of the Admin dashboard.
#private {
.__focus-ring-styles() {
// This uses the browser's default outline styles, rather than
// using custom ones, which could introduce more issues
// Source: https://css-tricks.com/copy-the-browsers-native-focus-styles
outline: 5px auto Highlight;
outline: 5px auto -webkit-focus-ring-color;
}
}
/**
* Adds a focus ring to an element.
*
* This is only shown when focus is provided via keyboard, using the
* `:focus-visible` selector, and `:-moz-focusring` for older Firefox.
*/
.add-keyboard-focus-ring() {
// We need to declare these separately, otherwise
// browsers will ignore `:focus-visible` as they
// don't understand `:-moz-focusring`
// These are the keyboard-only versions of :focus
&:-moz-focusring {
#private.__focus-ring-styles();
}
&:focus-visible {
#private.__focus-ring-styles();
}
}
/**
* This mixin allows support for a custom focus
* selector to be supplied.
*
* For example...
*
*? button { .addKeyboardFocusRing(":focus-within") }
* becomes
*? button:focus-within { <styles> }
*
* AND
*
*? button { .addKeyboardFocusRing(" :focus-within") }
* becomes
*? button :focus-within { <styles> }
*/
.add-keyboard-focus-ring(@customFocusSelector) {
@realFocusSelector: ~"@{customFocusSelector}";
&@{realFocusSelector} {
#private.__focus-ring-styles();
}
}
/**
* Allows an offset to be supplied for an a11y
* outline.
*
* Useful for elements whose content is right up
* against their bounds.
*
* `.addKeyboardFocusRingOffset(2px)` will add an
* offset of 2 pixels to the outline.
*/
.add-keyboard-focus-ring-offset(@offset) {
.offset() {
outline-offset: @offset;
}
&:-moz-focusring {
.offset();
}
&:focus-visible {
.offset();
}
}
/**
* Allows an offset to be supplied for an a11y
* outline.
*
* Useful for elements whose content is right up
* against their bounds.
*/
.add-keyboard-focus-ring-offset(@customSelector, @offset) {
.offset() {
outline-offset: @offset;
}
@realFocusSelector: ~"@{customFocusSelector}";
&@{realFocusSelector} {
.offset();
}
}