Focus ring helper and utilities (#33125)

* Add global variables for box-shadow focus rings

* Update instances of -btn-focus-box-shadow to use -ring-box-shadow, unless it's for buttons or inputs

* fix variable name

* Add CSS variables for global focus styling, document it

* Move to CSS vars section

* Update scss/_nav.scss

Co-authored-by: Gaël Poupard <[email protected]>

* Helper and utils

* Fix bundlewatch

* Change 'Focus ring' in sidebar so that the page can be visible

* Minor typo fix

* fix merge

* Revamp some more, improve docs

Co-authored-by: Gaël Poupard <[email protected]>
Co-authored-by: Julien Déramond <[email protected]>
Co-authored-by: Patrick H. Lauke <[email protected]>

6 files changed, 47 insertions, 8 deletions

diff --git a/scss/_helpers.scss b/scss/_helpers.scss
index 644b693fb..6126781cd 100644
--- a/scss/_helpers.scss
+++ b/scss/_helpers.scss
@@ -1,6 +1,7 @@
 @import "helpers/clearfix";
 @import "helpers/color-bg";
 @import "helpers/colored-links";
+@import "helpers/focus-ring";
 @import "helpers/ratio";
 @import "helpers/position";
 @import "helpers/stacks";
diff --git a/scss/_nav.scss b/scss/_nav.scss
index 1b3cf082f..3a27ee792 100644
--- a/scss/_nav.scss
+++ b/scss/_nav.scss
@@ -38,6 +38,11 @@
     text-decoration: if($link-hover-decoration == underline, none, null);
   }
 
+  &:focus {
+    outline: 0;
+    box-shadow: $nav-link-focus-box-shadow;
+  }
+
   // Disabled state lightens text
   &.disabled {
     color: var(--#{$prefix}nav-link-disabled-color);
diff --git a/scss/_root.scss b/scss/_root.scss
index 45de31090..323a5217b 100644
--- a/scss/_root.scss
+++ b/scss/_root.scss
@@ -127,6 +127,15 @@
   @each $name, $value in $grid-breakpoints {
     --#{$prefix}breakpoint-#{$name}: #{$value};
   }
+
+  // Focus styles
+  // scss-docs-start root-focus-variables
+  --#{$prefix}focus-ring-width: #{$focus-ring-width};
+  --#{$prefix}focus-ring-opacity: #{$focus-ring-opacity};
+  --#{$prefix}focus-ring-color: #{$focus-ring-color};
+  // By default, there is no `--bs-focus-ring-x`, `--bs-focus-ring-y`, or `--bs-focus-ring-blur`, but we provide CSS variables with fallbacks to initial `0` values
+  --#{$prefix}focus-ring-box-shadow: var(--#{$prefix}focus-ring-x, 0) var(--#{$prefix}focus-ring-y, 0) var(--#{$prefix}focus-ring-blur, 0) var(--#{$prefix}focus-ring-width) var(--#{$prefix}focus-ring-color);
+  // scss-docs-end root-focus-variables
 }
 
 @if $enable-dark-mode {
diff --git a/scss/_utilities.scss b/scss/_utilities.scss
index 4c2c39dd7..5134688e9 100644
--- a/scss/_utilities.scss
+++ b/scss/_utilities.scss
@@ -84,6 +84,14 @@ $utilities: map-merge(
       )
     ),
     // scss-docs-end utils-shadow
+    // scss-docs-start utils-focus-ring
+    "focus-ring": (
+      css-var: true,
+      css-variable-name: focus-ring-color,
+      class: focus-ring,
+      values: map-loop($theme-colors-rgb, rgba-css-var, "$key", "focus-ring")
+    ),
+    // scss-docs-end utils-focus-ring
     // scss-docs-start utils-position
     "position": (
       property: position,
diff --git a/scss/_variables.scss b/scss/_variables.scss
index 24a112a12..c22014015 100644
--- a/scss/_variables.scss
+++ b/scss/_variables.scss
@@ -549,6 +549,14 @@ $box-shadow-inset:            inset 0 1px 2px rgba(var(--#{$prefix}body-color-rg
 $component-active-color:      $white !default;
 $component-active-bg:         $primary !default;
 
+// scss-docs-start focus-ring-variables
+$focus-ring-width:      .25rem !default;
+$focus-ring-opacity:    .25 !default;
+$focus-ring-color:      rgba($primary, $focus-ring-opacity) !default;
+$focus-ring-blur:       0 !default;
+$focus-ring-box-shadow: 0 0 $focus-ring-blur $focus-ring-width $focus-ring-color !default;
+// scss-docs-end focus-ring-variables
+
 // scss-docs-start caret-variables
 $caret-width:                 .3em !default;
 $caret-vertical-align:        $caret-width * .85 !default;
@@ -761,11 +769,11 @@ $input-btn-font-family:       null !default;
 $input-btn-font-size:         $font-size-base !default;
 $input-btn-line-height:       $line-height-base !default;
 
-$input-btn-focus-width:         .25rem !default;
-$input-btn-focus-color-opacity: .25 !default;
-$input-btn-focus-color:         rgba($component-active-bg, $input-btn-focus-color-opacity) !default;
-$input-btn-focus-blur:          0 !default;
-$input-btn-focus-box-shadow:    0 0 $input-btn-focus-blur $input-btn-focus-width $input-btn-focus-color !default;
+$input-btn-focus-width:         $focus-ring-width !default;
+$input-btn-focus-color-opacity: $focus-ring-opacity !default;
+$input-btn-focus-color:         $focus-ring-color !default;
+$input-btn-focus-blur:          $focus-ring-blur !default;
+$input-btn-focus-box-shadow:    $focus-ring-box-shadow !default;
 
 $input-btn-padding-y-sm:      .25rem !default;
 $input-btn-padding-x-sm:      .5rem !default;
@@ -918,7 +926,7 @@ $form-check-input-border:                 var(--#{$prefix}border-width) solid va
 $form-check-input-border-radius:          .25em !default;
 $form-check-radio-border-radius:          50% !default;
 $form-check-input-focus-border:           $input-focus-border-color !default;
-$form-check-input-focus-box-shadow:       $input-btn-focus-box-shadow !default;
+$form-check-input-focus-box-shadow:       $focus-ring-box-shadow !default;
 
 $form-check-input-checked-color:          $component-active-color !default;
 $form-check-input-checked-bg-color:       $component-active-bg !default;
@@ -1124,6 +1132,8 @@ $nav-link-color:                    var(--#{$prefix}link-color) !default;
 $nav-link-hover-color:              var(--#{$prefix}link-hover-color) !default;
 $nav-link-transition:               color .15s ease-in-out, background-color .15s ease-in-out, border-color .15s ease-in-out !default;
 $nav-link-disabled-color:           var(--#{$prefix}secondary-color) !default;
+$nav-link-disabled-color:           $gray-600 !default;
+$nav-link-focus-box-shadow:         $focus-ring-box-shadow !default;
 
 $nav-tabs-border-color:             var(--#{$prefix}border-color) !default;
 $nav-tabs-border-width:             var(--#{$prefix}border-width) !default;
@@ -1265,7 +1275,7 @@ $pagination-border-color:           var(--#{$prefix}border-color) !default;
 
 $pagination-focus-color:            var(--#{$prefix}link-hover-color) !default;
 $pagination-focus-bg:               var(--#{$prefix}secondary-bg) !default;
-$pagination-focus-box-shadow:       $input-btn-focus-box-shadow !default;
+$pagination-focus-box-shadow:       $focus-ring-box-shadow !default;
 $pagination-focus-outline:          0 !default;
 
 $pagination-hover-color:            var(--#{$prefix}link-hover-color) !default;
@@ -1665,8 +1675,9 @@ $btn-close-height:           $btn-close-width !default;
 $btn-close-padding-x:        .25em !default;
 $btn-close-padding-y:        $btn-close-padding-x !default;
 $btn-close-color:            $black !default;
-$btn-close-bg:               url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='#{$btn-close-color}'><path d='M.293.293a1 1 0 0 1 1.414 0L8 6.586 14.293.293a1 1 0 1 1 1.414 1.414L9.414 8l6.293 6.293a1 1 0 0 1-1.414 1.414L8 9.414l-6.293 6.293a1 1 0 0 1-1.414-1.414L6.586 8 .293 1.707a1 1 0 0 1 0-1.414z'/></svg>") !default;
 $btn-close-focus-shadow:     $input-btn-focus-box-shadow !default;
+$btn-close-bg:               url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='#{$btn-close-color}'><path d='M.293.293a1 1 0 0 1 1.414 0L8 6.586 14.293.293a1 1 0 1 1 1.414 1.414L9.414 8l6.293 6.293a1 1 0 0 1-1.414 1.414L8 9.414l-6.293 6.293a1 1 0 0 1-1.414-1.414L6.586 8 .293 1.707a1 1 0 0 1 0-1.414z'/></svg>") !default;
+$btn-close-focus-shadow:     $focus-ring-box-shadow !default;
 $btn-close-opacity:          .5 !default;
 $btn-close-hover-opacity:    .75 !default;
 $btn-close-focus-opacity:    1 !default;
diff --git a/scss/helpers/_focus-ring.scss b/scss/helpers/_focus-ring.scss
new file mode 100644
index 000000000..26508a8d6
--- /dev/null
+++ b/scss/helpers/_focus-ring.scss
@@ -0,0 +1,5 @@
+.focus-ring:focus {
+  outline: 0;
+  // By default, there is no `--bs-focus-ring-x`, `--bs-focus-ring-y`, or `--bs-focus-ring-blur`, but we provide CSS variables with fallbacks to initial `0` values
+  box-shadow: var(--#{$prefix}focus-ring-x, 0) var(--#{$prefix}focus-ring-y, 0) var(--#{$prefix}focus-ring-blur, 0) var(--#{$prefix}focus-ring-width) var(--#{$prefix}focus-ring-color);
+}