feat(material/core): use strong focus indicators in high contrast mode

Reuses the strong focus indicators styling for high-contrast mode users.

Author: jackierchu

src/dev-app/theme.scss

@@ -33,12 +33,9 @@ $candy-app-theme: mat.define-light-theme((
 
 .demo-strong-focus {
   // Include base styles for strong focus indicators.
-  @include mat.strong-focus-indicators();
-  @include experimental.mdc-strong-focus-indicators();
-
-  // Include the default theme for focus indicators.
-  @include mat.strong-focus-indicators-theme($candy-app-theme);
-  @include experimental.mdc-strong-focus-indicators-theme($candy-app-theme);
+  $indicators-config: (border-color: mat.get-color-from-palette($candy-app-primary));
+  @include mat.strong-focus-indicators($indicators-config);
+  @include experimental.mdc-strong-focus-indicators($indicators-config);
 }
 
 // Include the alternative theme styles inside of a block with a CSS class. You can make this
@@ -60,8 +57,9 @@ $candy-app-theme: mat.define-light-theme((
 
   // Include the dark theme colors for focus indicators.
   &.demo-strong-focus {
-    @include mat.strong-focus-indicators-color($dark-colors);
-    @include experimental.mdc-strong-focus-indicators-color($dark-colors);
+    $indicators-config: (border-color: mat.get-color-from-palette($dark-primary));
+    @include mat.strong-focus-indicators($indicators-config);
+    @include experimental.mdc-strong-focus-indicators($indicators-config);
   }
 }
 

src/material-experimental/mdc-button/_button-base.scss

@@ -49,6 +49,10 @@
   .mat-mdc-focus-indicator {
     @include mat.private-fill();
   }
+
+  &:focus .mat-mdc-focus-indicator::before {
+    content: '';
+  }
 }
 
 // MDC's disabled buttons define a default cursor with pointer-events none. However, they select

src/material-experimental/mdc-button/button-high-contrast.scss

@@ -11,9 +11,3 @@
     outline: solid 1px;
   }
 }
-
-@include cdk.high-contrast(active, off) {
-  .mat-mdc-button-base:focus {
-    outline: solid 3px;
-  }
-}

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

@@ -107,3 +107,22 @@
   right: $offset;
   border-width: $offset;
 }
+
+// For the button element, default inset/offset values are necessary to ensure that
+// the focus indicator is sufficiently contrastive and renders appropriately.
+.mat-mdc-unelevated-button,
+.mat-mdc-raised-button {
+  .mat-mdc-focus-indicator::before {
+    $default-border-width: mat.$focus-indicators-private-default-border-width;
+    $border-width: var(--mat-mdc-focus-indicator-border-width, #{$default-border-width});
+    $offset: calc(#{$border-width} + 2px);
+    margin: calc(#{$offset} * -1);
+  }
+}
+
+.mat-mdc-outlined-button .mat-mdc-focus-indicator::before {
+  $default-border-width: mat.$focus-indicators-private-default-border-width;
+  $border-width: var(--mat-mdc-focus-indicator-border-width, #{$default-border-width});
+  $offset: calc(#{$border-width} + 3px);
+  margin: calc(#{$offset} * -1);
+}

src/material-experimental/mdc-button/fab.scss

@@ -65,6 +65,13 @@
   .mat-icon, .material-icons {
     @include mdc-fab.icon_();
   }
+
+  .mat-mdc-focus-indicator::before {
+    $default-border-width: mat.$focus-indicators-private-default-border-width;
+    $border-width: var(--mat-mdc-focus-indicator-border-width, #{$default-border-width});
+    $offset: calc(#{$border-width} + 2px);
+    margin: calc(#{$offset} * -1);
+  }
 }
 
 .mat-mdc-extended-fab {

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

@@ -1,4 +1,3 @@
-@use '@angular/cdk';
 @use '@angular/material' as mat;
 @use '@material/checkbox/checkbox' as mdc-checkbox;
 @use '@material/checkbox/checkbox-theme' as mdc-checkbox-theme;
@@ -49,11 +48,6 @@
     .mdc-checkbox__native-control:not([disabled]):focus ~ .mdc-checkbox__ripple {
       opacity: map.get(mdc-ripple.$dark-ink-opacities, hover) +
         map.get(mdc-ripple.$dark-ink-opacities, focus);
-
-      @include cdk.high-contrast(active, off) {
-        outline: solid 3px;
-        opacity: 1;
-      }
     }
   }
 
@@ -125,3 +119,15 @@
     $set-width: true,
     $query: mdc-helpers.$mat-base-styles-query);
 }
+
+// Checkbox components have to set `border-radius: 50%` in order to support density scaling
+// which will clip a square focus indicator so we have to turn it into a circle.
+.mat-mdc-checkbox-ripple::before {
+  border-radius: 50%;
+}
+
+// For checkboxes render the focus indicator when we know
+// the hidden input is focused (slightly different for each control).
+.mdc-checkbox__native-control:focus ~ .mat-mdc-focus-indicator::before {
+  content: '';
+}

src/material-experimental/mdc-chips/chip.scss

@@ -40,11 +40,6 @@
   @include cdk.high-contrast(active, off) {
     outline: solid 1px;
 
-    &.cdk-focused {
-      // Use 2px here since the dotted outline is a little thinner.
-      outline: dotted 2px;
-    }
-
     .mdc-evolution-chip__checkmark-path {
       // SVG colors won't be changed in high contrast mode and since the checkmark is white
       // by default, it'll blend in with the background in black-on-white mode. Override the
@@ -180,25 +175,42 @@
     left: 0;
     pointer-events: none;
   }
-}
 
-.mat-mdc-chip-remove {
-  .mat-icon {
-    width: inherit;
-    height: inherit;
-    font-size: inherit;
-    box-sizing: content-box;
+  // For the chip element, default inset/offset values are necessary to ensure that
+  // the focus indicator is sufficiently contrastive and renders appropriately.
+  .mat-mdc-focus-indicator::before {
+    $default-border-width: mat.$focus-indicators-private-default-border-width;
+    $border-width: var(--mat-mdc-focus-indicator-border-width, #{$default-border-width});
+    $offset: calc(#{$border-width} + 2px);
+    margin: calc(#{$offset} * -1);
   }
 }
 
-// Fades out the trailing icon slightly so that it can become darker when focused.
-// The MDC theming has variables for this, but the focus/hover states don't seem to work.
 .mat-mdc-chip-remove {
+  // Fades out the trailing icon slightly so that it can become darker when focused.
+  // The MDC theming has variables for this, but the focus/hover states don't seem to work.
   opacity: 0.54;
 
   &:focus {
     opacity: 1;
   }
+
+  &::before {
+    $default-border-width: mat.$focus-indicators-private-default-border-width;
+    $offset: var(--mat-mdc-focus-indicator-border-width, #{$default-border-width});
+    margin: calc(#{$offset} * -1);
+
+    // MDC sets a padding a on the chip button which stretches out the focus indicator.
+    left: 8px;
+    right: 8px;
+  }
+
+  .mat-icon {
+    width: inherit;
+    height: inherit;
+    font-size: inherit;
+    box-sizing: content-box;
+  }
 }
 
 .mat-chip-edit-input {
@@ -215,3 +227,8 @@
     outline-width: 3px;
   }
 }
+
+// In the chips the individual actions have focus so we target a different element.
+.mat-mdc-chip-action:focus .mat-mdc-focus-indicator::before {
+  content: '';
+}

src/material-experimental/mdc-core/option/option.scss

@@ -1,4 +1,3 @@
-@use '@angular/cdk';
 @use '@angular/material' as mat;
 @use '@material/list/evolution-mixins' as mdc-list-mixins;
 @use '@material/list/evolution-variables' as mdc-list-variables;
@@ -91,24 +90,7 @@
   }
 }
 
-.mat-mdc-option-active {
-  @include cdk.high-contrast(active, off) {
-    // A pseudo element is used here, because the active indication gets moved between options
-    // and we don't want the border from below to shift the layout around as it's added and removed.
-    &::before {
-      content: '';
-      position: absolute;
-      top: 0;
-      bottom: 0;
-      left: 0;
-      right: 0;
-      pointer-events: none;
-
-      // We use a border here, rather than an outline, because the outline will be cut off
-      // by the `overflow: hidden` on the panel wrapping the options, whereas a border
-      // will push the element inwards. This could be done using `outline-offset: -1px`,
-      // however the property isn't supported on IE11.
-      border: solid 1px currentColor;
-    }
-  }
+// For options, render the focus indicator when the class .mat-mdc-option-active is present.
+.mat-mdc-option-active::before {
+  content: '';
 }

src/material-experimental/mdc-helpers/_focus-indicators-theme.scss

@@ -2,28 +2,28 @@
 @use 'sass:map';
 @use 'sass:meta';
 
-@mixin _border-color($color) {
-  .mat-mdc-focus-indicator::before {
-    border-color: $color;
-  }
-}
-
 // stylelint-disable-next-line material/theme-mixin-api
 @mixin color($config-or-theme-or-color) {
   @if meta.type-of($config-or-theme-or-color) == 'color' {
-    @include _border-color($config-or-theme-or-color);
+    @include mat.focus-indicators-private-private-customize-focus-indicators((
+      border-color: $config-or-theme-or-color
+    ), 'mat-mdc');
   }
   @else {
     $config: mat.get-color-config($config-or-theme-or-color);
     $border-color: mat.get-color-from-palette(map.get($config, primary));
-    @include _border-color($border-color);
+    @include mat.focus-indicators-private-private-customize-focus-indicators((
+      border-color: $border-color
+    ), 'mat-mdc');
   }
 }
 
 // stylelint-disable-next-line material/theme-mixin-api
 @mixin theme($theme-or-color-config-or-color) {
   @if meta.type-of($theme-or-color-config-or-color) == 'color' {
-    @include _border-color($theme-or-color-config-or-color);
+    @include mat.focus-indicators-private-private-customize-focus-indicators((
+      border-color: $theme-or-color-config-or-color
+    ), 'mat-mdc');
   }
   @else {
     $theme: mat.private-legacy-get-theme($theme-or-color-config-or-color);

src/material-experimental/mdc-helpers/_focus-indicators.scss

@@ -1,104 +1,15 @@
-@use '@angular/material' as mat;
 @use 'sass:map';
+@use '@angular/material' as mat;
 
-/// Mixin that turns on strong focus indicators.
-///
-/// @example
-///   .my-app {
-///     @include mat-mdc-strong-focus-indicators($config);
-///   }
 @mixin strong-focus-indicators($config: ()) {
   // Default focus indicator config.
   $default-config: (
-    border-style: solid,
-    border-width: 3px,
-    border-radius: 4px,
+    border-color: black,
+    display: block,
   );
 
   // Merge default config with user config.
   $config: map.merge($default-config, $config);
-  $border-style: map.get($config, border-style);
-  $border-width: map.get($config, border-width);
-  $border-radius: map.get($config, border-radius);
-
-  // Base styles for focus indicators.
-  .mat-mdc-focus-indicator::before {
-    @include mat.private-fill();
-    box-sizing: border-box;
-    pointer-events: none;
-    border: $border-width $border-style transparent;
-    border-radius: $border-radius;
-
-    .cdk-high-contrast-active & {
-      display: none;
-    }
-  }
-
-  // By default, all focus indicators are flush with the bounding box of their
-  // host element. For particular elements (listed below), default inset/offset
-  // values are necessary to ensure that the focus indicator is sufficiently
-  // contrastive and renders appropriately.
-
-  .mat-mdc-unelevated-button .mat-mdc-focus-indicator::before,
-  .mat-mdc-raised-button .mat-mdc-focus-indicator::before,
-  .mdc-fab .mat-mdc-focus-indicator::before,
-  .mat-mdc-chip-action-label .mat-mdc-focus-indicator::before {
-    margin: -($border-width + 2px);
-  }
-
-  .mat-mdc-outlined-button .mat-mdc-focus-indicator::before {
-    margin: -($border-width + 3px);
-  }
-
-  .mat-mdc-focus-indicator.mat-mdc-chip-remove::before {
-    margin: -$border-width;
-  }
-
-  // MDC sets a padding a on the button which stretches out the focus indicator.
-  .mat-mdc-focus-indicator.mat-mdc-chip-remove::before {
-    left: 8px;
-    right: 8px;
-  }
-
-  .mat-mdc-focus-indicator.mat-mdc-tab::before,
-  .mat-mdc-focus-indicator.mat-mdc-tab-link::before {
-    margin: 5px;
-  }
-
-  // These components have to set `border-radius: 50%` in order to support density scaling
-  // which will clip a square focus indicator so we have to turn it into a circle.
-  .mat-mdc-checkbox-ripple.mat-mdc-focus-indicator::before,
-  .mat-radio-ripple.mat-mdc-focus-indicator::before,
-  .mat-mdc-slider .mat-mdc-focus-indicator::before,
-  .mat-mdc-slide-toggle .mat-mdc-focus-indicator::before {
-    border-radius: 50%;
-  }
-
-  // Render the focus indicator on focus. Defining a pseudo element's
-  // content will cause it to render.
-
-  // For checkboxes, radios and slide toggles, render the focus indicator when we know
-  // the hidden input is focused (slightly different for each control).
-  .mdc-checkbox__native-control:focus ~ .mat-mdc-focus-indicator::before,
-  .mat-mdc-slide-toggle-focused .mat-mdc-focus-indicator::before,
-  .mat-mdc-radio-button.cdk-focused .mat-mdc-focus-indicator::before,
-
-  // In the chips the individual actions have focus so we target a different element.
-  .mat-mdc-chip-action:focus .mat-mdc-focus-indicator::before,
-
-  // For buttons and list items, render the focus indicator when the parent
-  // button or list item is focused.
-  .mat-mdc-button-base:focus .mat-mdc-focus-indicator::before,
-  .mat-mdc-list-item:focus > .mat-mdc-focus-indicator::before,
-
-  // For options, render the focus indicator when the class .mat-mdc-option-active is present.
-  .mat-mdc-focus-indicator.mat-mdc-option-active::before,
-
-  // In the MDC slider the focus indicator is inside the thumb.
-  .mdc-slider__thumb--focused .mat-mdc-focus-indicator::before,
 
-    // For all other components, render the focus indicator on focus.
-  .mat-mdc-focus-indicator:focus::before {
-    content: '';
-  }
+  @include mat.focus-indicators-private-private-customize-focus-indicators($config, 'mat-mdc');
 }

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

@@ -58,9 +58,17 @@
 // The MDC-based list items already use the `::before` pseudo element for the standard
 // focus/selected/hover state. Hence, we need to have a separate list-item spanning
 // element that can be used for strong focus indicators.
-.mat-mdc-list-item > .mat-mdc-focus-indicator {
-  @include mat.private-fill();
-  pointer-events: none;
+.mat-mdc-list-item {
+  & > .mat-mdc-focus-indicator {
+    @include mat.private-fill();
+    pointer-events: none;
+  }
+
+  // For list items, render the focus indicator when the parent
+  // listem item is focused.
+  &:focus > .mat-mdc-focus-indicator::before {
+    content: '';
+  }
 }
 
 .mat-mdc-list-item.mdc-list-item--with-three-lines {