Improve gradients

- Use a semitransparent gradient from light to dark which works on any background-color
- Store the gradient as a custom property (--bs-gradient)
- Remove `.bg-gradient-*` variants in favour of `.bg-gradient` which works even when `$enable-gradients` are enabled
- Add gradients to navbar, active page links and badges when gradients are enabled

scss/_badge.scss

@@ -14,6 +14,7 @@
   white-space: nowrap;
   vertical-align: baseline;
   @include border-radius($badge-border-radius);
+  @include gradient-bg();
 
   // Empty badges collapse automatically
   &:empty {

scss/_helpers.scss

@@ -1,4 +1,3 @@
-@import "helpers/background";
 @import "helpers/clearfix";
 @import "helpers/colored-links";
 @import "helpers/embed";

scss/_mixins.scss

@@ -30,7 +30,6 @@
 @import "mixins/table-variants";
 
 // Skins
-@import "mixins/background-variant";
 @import "mixins/border-radius";
 @import "mixins/box-shadow";
 @import "mixins/gradients";

scss/_nav.scss

@@ -82,7 +82,7 @@
   .nav-link.active,
   .show > .nav-link {
     color: $nav-pills-link-active-color;
-    background-color: $nav-pills-link-active-bg;
+    @include gradient-bg($nav-pills-link-active-bg);
   }
 }
 

scss/_navbar.scss

@@ -24,6 +24,7 @@
   padding-right: $navbar-padding-x; // default: null
   padding-bottom: $navbar-padding-y;
   padding-left: $navbar-padding-x; // default: null
+  @include gradient-bg();
 
   // Because flex properties aren't inherited, we need to redeclare these first
   // few properties so that content nested within behave properly.

scss/_pagination.scss

@@ -34,7 +34,7 @@
   &.active .page-link {
     z-index: 3;
     color: $pagination-active-color;
-    background-color: $pagination-active-bg;
+    @include gradient-bg($pagination-active-bg);
     border-color: $pagination-active-border-color;
   }
 

scss/_root.scss

@@ -12,4 +12,5 @@
   // See https://github.com/sass/sass/issues/2383#issuecomment-336349172
   --bs-font-sans-serif: #{inspect($font-family-sans-serif)};
   --bs-font-monospace: #{inspect($font-family-monospace)};
+  --bs-gradient: #{$gradient};
 }

scss/_utilities.scss

@@ -416,6 +416,11 @@ $utilities: map-merge(
         )
       )
     ),
+    "gradient": (
+      property: background-image,
+      class: bg,
+      values: (gradient: var(--bs-gradient))
+    ),
     "white-space": (
       property: white-space,
       class: text,

scss/_variables.scss

@@ -222,6 +222,11 @@ $enable-negative-margins:     false !default;
 $enable-deprecation-messages: true !default;
 $enable-important-utilities:  true !default;
 
+// Gradient
+//
+// The gradient which is added to components if `$enable-gradients` is `true`
+// This gradient is also added to elements with `.bg-gradient`
+$gradient: linear-gradient(180deg, rgba($white, .15), rgba($white, 0)) !default;
 
 // Spacing
 //

scss/forms/_form-check.scss

@@ -53,7 +53,7 @@
 
     &[type="checkbox"] {
       @if $enable-gradients {
-        background-image: escape-svg($form-check-input-checked-bg-image), linear-gradient(180deg, lighten($form-check-input-checked-bg-color, 10%), $form-check-input-checked-bg-color);
+        background-image: escape-svg($form-check-input-checked-bg-image), var(--bs-gradient);
       } @else {
         background-image: escape-svg($form-check-input-checked-bg-image);
       }
@@ -61,7 +61,7 @@
 
     &[type="radio"] {
       @if $enable-gradients {
-        background-image: escape-svg($form-check-radio-checked-bg-image), linear-gradient(180deg, lighten($form-check-input-checked-bg-color, 10%), $form-check-input-checked-bg-color);
+        background-image: escape-svg($form-check-radio-checked-bg-image), var(--bs-gradient);
       } @else {
         background-image: escape-svg($form-check-radio-checked-bg-image);
       }
@@ -73,7 +73,7 @@
     border-color: $form-check-input-indeterminate-border-color;
 
     @if $enable-gradients {
-      background-image: escape-svg($form-check-input-indeterminate-bg-image), linear-gradient(180deg, lighten($form-check-input-checked-bg-color, 10%), $form-check-input-checked-bg-color);
+      background-image: escape-svg($form-check-input-indeterminate-bg-image), var(--bs-gradient);
     } @else {
       background-image: escape-svg($form-check-input-indeterminate-bg-image);
     }

scss/helpers/_background.scss

@@ -1,5 +0,0 @@
-@if $enable-gradients {
-  @each $color, $value in $theme-colors {
-    @include bg-gradient-variant(".bg-gradient-#{$color}", $value);
-  }
-}

scss/mixins/_background-variant.scss

@@ -1,7 +0,0 @@
-// stylelint-disable declaration-no-important
-
-@mixin bg-gradient-variant($parent, $color) {
-  #{$parent} {
-    background-image: linear-gradient(180deg, mix($body-bg, $color, 15%), $color) !important;
-  }
-}

scss/mixins/_forms.scss

@@ -97,7 +97,7 @@
       border-color: $color;
 
       &:checked {
-        @include gradient-bg(lighten($color, 10%), escape-svg($form-check-input-checked-bg-image));
+        background-color: $color;
       }
 
       &:focus {

scss/mixins/_gradients.scss

@@ -1,14 +1,10 @@
 // Gradients
 
-@mixin gradient-bg($color, $foreground: null) {
+@mixin gradient-bg($color: null) {
+  background-color: $color;
+
   @if $enable-gradients {
-    @if $foreground {
-      background-image: $foreground, linear-gradient(180deg, mix($body-bg, $color, 15%), $color);
-    } @else {
-      background-image: linear-gradient(180deg, mix($body-bg, $color, 15%), $color);
-    }
-  } @else {
-    background-color: $color;
+    background-image: var(--bs-gradient);
   }
 }