fix(components): implement :host-context fallback for firefox and safari

packages/components/src/components/post-card-control/post-card-control.module.scss

@@ -0,0 +1,5 @@
+@use '@swisspost/design-system-styles/core' as post;
+
+:export {
+  dark-bg-selectors: [post.$dark-backgrounds];
+}

packages/components/src/components/post-card-control/post-card-control.scss

@@ -177,3 +177,70 @@
     }
   }
 }
+
+// remove as soon as all browser support :host-context()
+// https://caniuse.com/?search=%3Ahost-context()
+:host(:not(:last-child)) {
+  .card-control[data-host-context*='fieldset'] {
+    margin-bottom: post.$size-regular;
+  }
+}
+
+@each $bg in post.$dark-backgrounds {
+  .card-control[data-host-context*='#{$bg}'] {
+    --post-card-control-border-color: #{post.$white};
+    --post-card-control-bg: transparent;
+    --post-card-control-color: #{post.$white};
+    --post-card-control-input-border-color: #{post.$white};
+    --post-card-control-input-bg: transparent;
+
+    &:not(.is-disabled) {
+      // order matters!
+      // because we only overwrite the props, which need to be different from one selector to the other.
+
+      &.is-checked {
+        --post-card-control-border-color: #{post.$yellow};
+        --post-card-control-bg: #{post.$yellow};
+        --post-card-control-color: #{post.$gray-80};
+        --post-card-control-input-border-color: #{post.$gray-80};
+        --post-card-control-input-bg: #{post.$white};
+
+        &.is-invalid {
+          --post-card-control-bg: #{post.$yellow};
+        }
+      }
+
+      &.is-invalid {
+        --post-card-control-border-color: #{post.$danger};
+        --post-card-control-bg: #{post.$error-background};
+        --post-card-control-color: #{post.$danger};
+        --post-card-control-input-border-color: #{post.$danger};
+        --post-card-control-input-bg: #{post.$white};
+      }
+
+      &:hover {
+        --post-card-control-border-color: #{post.$black};
+        --post-card-control-bg: #{post.$gray-20};
+        --post-card-control-color: #{post.$black};
+        --post-card-control-input-border-color: #{post.$black};
+        --post-card-control-input-bg: #{post.$white};
+      }
+    }
+
+    // show focus even if is-disabled, because aria-disabled allows focus at any moment
+    &.is-focused {
+      &:where(:has(.card-control--input:focus-visible)) {
+        outline-color: post.$white;
+      }
+    }
+
+    // TODO: update white alpha colors with design-system alpha colors, once they are defined
+    &.is-disabled {
+      --post-card-control-border-color: #{#{rgba(post.$white, 0.8)}};
+      --post-card-control-bg: transparent;
+      --post-card-control-color: #{#{rgba(post.$white, 0.8)}};
+      --post-card-control-input-border-color: #{#{rgba(post.$white, 0.8)}};
+      --post-card-control-input-bg: transparent;
+    }
+  }
+}

packages/components/src/components/post-card-control/post-card-control.tsx

@@ -14,6 +14,13 @@ import {
 import { checkNonEmpty, checkOneOf } from '../../utils';
 import { version } from '../../../package.json';
 
+// remove as soon as all browser support :host-context()
+// https://caniuse.com/?search=%3Ahost-context()
+import scss from './post-card-control.module.scss';
+import { parse } from '../../utils/sass-export';
+
+const SCSS_VARIABLES = parse(scss);
+
 let cardControlIds = 0;
 
 /**
@@ -49,10 +56,10 @@ export class PostCardControl {
 
   private control: HTMLInputElement;
   private controlId = `PostCardControl_${cardControlIds++}`;
+  private initialChecked: boolean;
 
   @Element() host: HTMLPostCardControlElement;
 
-  @State() initialChecked: boolean;
   @State() focused = false;
 
   @AttachInternals() private internals: ElementInternals;
@@ -296,11 +303,34 @@ export class PostCardControl {
     this.groupCollectMembers();
   }
 
-  connectedCallback() {
-    this.initialChecked = this.checked;
+  // remove as soon as all browser support the :host-context() selector
+  private readonly HOST_CONTEXT_FILTERS = ['fieldset', ...SCSS_VARIABLES['dark-bg-selectors']];
+  private hostContext: string[];
+
+  private setHostContext() {
+    this.hostContext = [];
+    let element = this.host as HTMLElement;
+
+    while (element) {
+      const localName = element.localName;
+      const id = element.id ? `#${element.id}` : '';
+      const classes =
+        element.classList.length > 0 ? `.${Array.from(element.classList).join('.')}` : '';
+
+      this.hostContext.push(`${localName}${id}${classes}`);
+      element = element.parentElement;
+    }
+
+    this.hostContext = this.hostContext.filter(ctx =>
+      this.HOST_CONTEXT_FILTERS.find(f => ctx.includes(f)),
+    );
   }
 
-  componentWillLoad() {
+  connectedCallback() {
+    // remove as soon as all browser support :host-context()
+    this.setHostContext();
+
+    this.initialChecked = this.checked;
     this.validateControlLabel();
     this.validateControlType();
   }
@@ -317,6 +347,8 @@ export class PostCardControl {
             'is-valid': this.validity !== null && this.validity !== 'false',
             'is-invalid': this.validity === 'false',
           }}
+          // remove as soon as all browser support :host-context()
+          data-host-context={this.hostContext.join(' ')}
         >
           <input
             ref={el => (this.control = el as HTMLInputElement)}