Fix display issues of close button in contextual light and dark modes (#41126)

Author: julien-deramond

scss/_close.scss

@@ -12,7 +12,6 @@
   --#{$prefix}btn-close-focus-shadow: #{$btn-close-focus-shadow};
   --#{$prefix}btn-close-focus-opacity: #{$btn-close-focus-opacity};
   --#{$prefix}btn-close-disabled-opacity: #{$btn-close-disabled-opacity};
-  --#{$prefix}btn-close-white-filter: #{$btn-close-white-filter};
   // scss-docs-end close-css-vars
 
   box-sizing: content-box;
@@ -21,6 +20,7 @@
   padding: $btn-close-padding-y $btn-close-padding-x;
   color: var(--#{$prefix}btn-close-color);
   background: transparent var(--#{$prefix}btn-close-bg) center / $btn-close-width auto no-repeat; // include transparent for button elements
+  filter: var(--#{$prefix}btn-close-filter);
   border: 0; // for button elements
   @include border-radius();
   opacity: var(--#{$prefix}btn-close-opacity);
@@ -47,17 +47,20 @@
 }
 
 @mixin btn-close-white() {
-  filter: var(--#{$prefix}btn-close-white-filter);
+  --#{$prefix}btn-close-filter: #{$btn-close-filter-dark};
 }
 
 .btn-close-white {
   @include btn-close-white();
 }
 
+:root,
+[data-bs-theme="light"] {
+  --#{$prefix}btn-close-filter: #{$btn-close-filter};
+}
+
 @if $enable-dark-mode {
-  @include color-mode(dark) {
-    .btn-close {
-      @include btn-close-white();
-    }
+  @include color-mode(dark, true) {
+    @include btn-close-white();
   }
 }

scss/_variables-dark.scss

@@ -94,3 +94,9 @@ $accordion-button-active-icon-dark:  url("data:image/svg+xml,<svg xmlns='http://
 $carousel-indicator-active-bg-dark:   $carousel-dark-indicator-active-bg !default;
 $carousel-caption-color-dark:         $carousel-dark-caption-color !default;
 $carousel-control-icon-filter-dark:   $carousel-dark-control-icon-filter !default;
+
+//
+// Close button
+//
+
+$btn-close-filter-dark:             $btn-close-white-filter !default;

scss/_variables.scss

@@ -1713,7 +1713,8 @@ $btn-close-opacity:          .5 !default;
 $btn-close-hover-opacity:    .75 !default;
 $btn-close-focus-opacity:    1 !default;
 $btn-close-disabled-opacity: .25 !default;
-$btn-close-white-filter:     invert(1) grayscale(100%) brightness(200%) !default;
+$btn-close-filter:           null !default;
+$btn-close-white-filter:     invert(1) grayscale(100%) brightness(200%) !default; // Deprecated in v5.3.4
 // scss-docs-end close-variables