fix(material-experimental/mdc-radio): switch to new theming API (#23725)

Reworks the MDC-based radio button to use the new theming API based on CSS variables.

Also fixes a minor issue where the high contrast styles were emitting slightly more CSS than they need to.

Co-authored-by: Kristiyan Kostadinov <crisbeto@abv.bg>

Author: zarend

src/material-experimental/mdc-radio/_radio-theme.scss

@@ -1,3 +1,4 @@
+@use 'sass:map';
 @use '@material/theme/theme-color' as mdc-theme-color;
 @use '@material/radio/radio-theme' as mdc-radio-theme;
 @use '@material/radio/radio' as mdc-radio;
@@ -6,42 +7,59 @@
 @use '../../material/core/typography/typography';
 @use '../../material/core/theming/theming';
 
+@mixin _color-palette($color-palette) {
+  @include mdc-radio-theme.theme((
+    selected-focus-icon-color: $color-palette,
+    selected-focus-state-layer-color: $color-palette,
+    selected-hover-icon-color: $color-palette,
+    selected-hover-state-layer-color: $color-palette,
+    selected-icon-color: $color-palette,
+    selected-pressed-icon-color: $color-palette,
+    selected-pressed-state-layer-color: $color-palette,
+  ));
+
+  // TODO(crisbeto): this should be included by MDC's `theme-styles`, but it isn't currently.
+  @include mdc-radio-theme.focus-indicator-color($color-palette);
+}
+
 @mixin color($config-or-theme) {
   $config: theming.get-color-config($config-or-theme);
-  // Save original values of MDC global variables. We need to save these so we can restore the
-  // variables to their original values and prevent unintended side effects from using this mixin.
-  $orig-baseline-theme-color: mdc-radio-theme.$baseline-theme-color;
-  $orig-unchecked-color: mdc-radio-theme.$unchecked-color;
-  $orig-disabled-circle-color: mdc-radio-theme.$disabled-circle-color;
+  $primary: theming.get-color-from-palette(map.get($config, primary));
+  $accent: theming.get-color-from-palette(map.get($config, accent));
+  $warn: theming.get-color-from-palette(map.get($config, warn));
 
   @include mdc-helpers.mat-using-mdc-theme($config) {
-    mdc-radio-theme.$baseline-theme-color: primary;
-    mdc-radio-theme.$unchecked-color: rgba(mdc-theme-color.prop-value(on-surface), 0.54);
-    mdc-radio-theme.$disabled-circle-color: rgba(mdc-theme-color.prop-value(on-surface), 0.38);
+    $on-surface: rgba(mdc-theme-color.$on-surface, 0.54);
 
     .mat-mdc-radio-button {
       @include mdc-form-field.core-styles($query: mdc-helpers.$mat-theme-styles-query);
+      @include mdc-radio-theme.theme((
+        // The disabled colors don't use the `rgba` version, because
+        // MDC applies a separate opacity to disabled buttons.
+        disabled-selected-icon-color: mdc-theme-color.$on-surface,
+        disabled-unselected-icon-color: mdc-theme-color.$on-surface,
+        unselected-focus-icon-color: $on-surface,
+        unselected-focus-state-layer-color: $on-surface,
+        unselected-hover-icon-color: $on-surface,
+        unselected-hover-state-layer-color: $on-surface,
+        unselected-icon-color: $on-surface,
+        unselected-pressed-icon-color: $on-surface,
+        unselected-pressed-state-layer-color: $on-surface,
+      ));
 
       &.mat-primary {
-        @include mdc-radio.without-ripple($query: mdc-helpers.$mat-theme-styles-query);
+        @include _color-palette($primary);
       }
 
       &.mat-accent {
-        mdc-radio-theme.$baseline-theme-color: secondary;
-        @include mdc-radio.without-ripple($query: mdc-helpers.$mat-theme-styles-query);
+        @include _color-palette($accent);
       }
 
       &.mat-warn {
-        mdc-radio-theme.$baseline-theme-color: error;
-        @include mdc-radio.without-ripple($query: mdc-helpers.$mat-theme-styles-query);
+        @include _color-palette($warn);
       }
     }
   }
-
-  // Restore original values of MDC global variables.
-  mdc-radio-theme.$baseline-theme-color: $orig-baseline-theme-color;
-  mdc-radio-theme.$unchecked-color: $orig-unchecked-color;
-  mdc-radio-theme.$disabled-circle-color: $orig-disabled-circle-color;
 }
 
 @mixin typography($config-or-theme) {

src/material-experimental/mdc-radio/radio.scss

@@ -9,21 +9,28 @@
 @include mdc-radio.without-ripple($query: mdc-helpers.$mat-base-styles-without-animation-query);
 @include mdc-form-field.core-styles($query: mdc-helpers.$mat-base-styles-query);
 
-// This is necessary because we do not depend on MDC's ripple, but have our own that should be
-// positioned correctly. This can be removed once we start using MDC's ripple implementation.
-.mat-mdc-radio-button .mat-radio-ripple {
-  @include layout-common.fill;
-
-  pointer-events: none;
-  border-radius: 50%;
+.mat-mdc-radio-button {
+  &:not(._mat-animation-noopable) {
+    @include mdc-radio.without-ripple($query: animation);
+  }
 
-  .mat-ripple-element:not(.mat-radio-persistent-ripple) {
-    opacity: mdc-radio-theme.$ripple-opacity;
+  .mdc-radio {
+    // MDC theme styles also include structural styles so we have to include the theme at least
+    // once here. The values will be overwritten by our own theme file afterwards.
+    @include mdc-radio-theme.theme-styles(mdc-radio-theme.$light-theme);
   }
-}
 
-.mat-mdc-radio-button:not(._mat-animation-noopable) {
-  @include mdc-radio.without-ripple($query: animation);
+  // This is necessary because we do not depend on MDC's ripple, but have our own that should be
+  // positioned correctly. This can be removed once we start using MDC's ripple implementation.
+  .mat-radio-ripple {
+    @include layout-common.fill;
+    pointer-events: none;
+    border-radius: 50%;
+
+    .mat-ripple-element:not(.mat-radio-persistent-ripple) {
+      opacity: mdc-radio-theme.$ripple-opacity;
+    }
+  }
 }
 
 // Element used to provide a larger tap target for users on touch devices.
@@ -42,7 +49,7 @@
 // Note that this creates a square box around the circle, however it's consistent with
 // how IE/Edge treat native radio buttons in high contrast mode. We can't turn the border
 // into a dotted one, because it's too thick which causes the circles to look off.
-@include a11y.high-contrast {
+@include a11y.high-contrast(active, 'off') {
   .mat-mdc-radio-button:not(.mat-radio-disabled) {
     &.cdk-keyboard-focused,
     &.cdk-program-focused {