feat(ripple): Add support for activated and selected states

packages/mdc-ripple/README.md

@@ -62,7 +62,7 @@ General notes:
 
 #### Sass API
 
-In order to fully style states as well as the ripple effect for pressed state, both `mdc-ripple` mixins below must be included, as well as either the basic `mdc-states` mixin or all of the advanced `mdc-states-...` mixins documented below.
+In order to fully style states as well as the ripple effect for pressed state, both `mdc-ripple` mixins below must be included, as well as either the basic or advanced `mdc-states` mixins documented below.
 
 Once these styles are in place for a component, it is feasible to further override only the parts necessary (e.g. `mdc-states` specifically) for specific variants (e.g. for flat vs. raised buttons).
 
@@ -75,14 +75,26 @@ Mixin | Description
 `mdc-ripple-surface` | Adds base styles for a ripple surface
 `mdc-ripple-radius($radius)` | Adds styles for the radius of the ripple effect,<br>for both bounded and unbounded ripples
 
-##### Basic States Mixin
+##### Basic States Mixins
+
+When using the basic states mixins, inclusion of the `mdc-states` mixin is mandatory.
+Inclusion of `mdc-states-activated` or `mdc-states-selected` is optional, depending on whether activated or selected
+states are applicable to the component in question.
 
 Mixin | Description
 --- | ---
-`mdc-states($color, $has-nested-focusable-element)` | Adds state and ripple styles for the indicated color, deciding opacities based on whether the passed color is light or dark. `$has-nested-focusable-element` defaults to `false` but should be set to `true` if the component contains a focusable element (e.g. an input) under the root node.
+`mdc-states($color, $has-nested-focusable-element)` | Adds state and ripple styles using the indicated color, deciding opacities based on whether the passed color is light or dark.<br>`$has-nested-focusable-element` defaults to `false` but should be set to `true` if the component contains a focusable element (e.g. an input) under the root node.
+`mdc-states-activated($color, $has-nested-focusable-element)` | Adds state and ripple styles for activated states using the indicated color, deciding opacities based on whether the passed color is light or dark.<br>`$has-nested-focusable-element` defaults to `false` but should be set to `true` if the component contains a focusable element (e.g. an input) under the root node.
+`mdc-states-selected($color, $has-nested-focusable-element)` | Adds state and ripple styles for selected states using the indicated color, deciding opacities based on whether the passed color is light or dark.<br>`$has-nested-focusable-element` defaults to `false` but should be set to `true` if the component contains a focusable element (e.g. an input) under the root node.
 
 ##### Advanced States Mixins
 
+When using the advanced states mixins, every one of the mixins below should be included at least once to establish base
+styles for states.
+
+These mixins can also be used to emit activated or selected styles if applicable, by applying them within a selector for
+`&--activated` or `&--selected` modifier classes.
+
 Mixin | Description
 --- | ---
 `mdc-states-base-color($color)` | Sets up base state styles using the provided color

packages/mdc-ripple/_mixins.scss

@@ -61,6 +61,7 @@ $mdc-ripple-common-styles-emitted_: false !default;
   &::after {
     position: absolute;
     border-radius: 50%;
+    opacity: 0;
     pointer-events: none;
     content: "";
     will-change: transform, opacity;
@@ -104,8 +105,6 @@ $mdc-ripple-common-styles-emitted_: false !default;
   &::before,
   &::after {
     @include mdc-theme-prop(background-color, $color, $edgeOptOut: true);
-
-    opacity: 0;
   }
 }
 
@@ -156,19 +155,43 @@ $mdc-ripple-common-styles-emitted_: false !default;
   }
 }
 
-// Simple mixin which automatically selects opacity values based on whether the ink color is light or dark.
+// Simple mixin for base states which automatically selects opacity values based on whether the ink color is
+// light or dark.
 @mixin mdc-states($color: black, $has-nested-focusable-element: false) {
-  $color-value: mdc-theme-prop-value($color);
-  $opacity-map: if(
-    mdc-theme-tone($color-value) == "light",
-    $mdc-ripple-light-ink-opacities,
-    $mdc-ripple-dark-ink-opacities
-  );
+  @include mdc-states-interactions_($color, $has-nested-focusable-element);
+}
 
-  @include mdc-states-base-color($color);
-  @include mdc-states-hover-opacity(map-get($opacity-map, "hover"));
-  @include mdc-states-focus-opacity(map-get($opacity-map, "focus"), $has-nested-focusable-element);
-  @include mdc-states-press-opacity(map-get($opacity-map, "press"));
+// Simple mixin for activated states which automatically selects opacity values based on whether the ink color is
+// light or dark.
+@mixin mdc-states-activated($color, $has-nested-focusable-element: false) {
+  $opacity-map: mdc-states-opacities_($color);
+  $activated-opacity: map-get($opacity-map, "activated");
+
+  &--activated {
+    // Stylelint seems to think that '&' qualifies as a type selector here?
+    // stylelint-disable-next-line selector-max-type
+    &::before {
+      opacity: $activated-opacity;
+    }
+
+    @include mdc-states-interactions_($color, $has-nested-focusable-element, $activated-opacity);
+  }
+}
+
+// Simple mixin for selected states which automatically selects opacity values based on whether the ink color is
+// light or dark.
+@mixin mdc-states-selected($color, $has-nested-focusable-element: false) {
+  $opacity-map: mdc-states-opacities_($color);
+  $selected-opacity: map-get($opacity-map, "selected");
+
+  &--selected {
+    // stylelint-disable-next-line selector-max-type
+    &::before {
+      opacity: $selected-opacity;
+    }
+
+    @include mdc-states-interactions_($color, $has-nested-focusable-element, $selected-opacity);
+  }
 }
 
 @mixin mdc-ripple-radius($radius: 100%) {
@@ -250,6 +273,27 @@ $mdc-ripple-common-styles-emitted_: false !default;
 // Private
 //
 
+@function mdc-states-opacities_($color) {
+  $color-value: mdc-theme-prop-value($color);
+  $opacity-map: if(
+    mdc-theme-tone($color-value) == "light",
+    $mdc-ripple-light-ink-opacities,
+    $mdc-ripple-dark-ink-opacities
+  );
+
+  @return $opacity-map;
+}
+
+@mixin mdc-states-interactions_($color, $has-nested-focusable-element, $opacity-modifier: 0) {
+  $opacity-map: mdc-states-opacities_($color);
+
+  @include mdc-states-base-color($color);
+  @include mdc-states-hover-opacity(map-get($opacity-map, "hover") + $opacity-modifier);
+  @include mdc-states-focus-opacity(map-get($opacity-map, "focus") + $opacity-modifier, $has-nested-focusable-element);
+  @include mdc-states-press-opacity(map-get($opacity-map, "press") + $opacity-modifier);
+}
+
+// Note: This can be removed when we remove the legacy mdc-ripple-color mixin.
 @mixin mdc-ripple-color_($color, $opacity) {
   // stylelint-disable at-rule-empty-line-before, block-closing-brace-newline-after
   @if type-of($color) == "color" {

packages/mdc-ripple/_variables.scss

@@ -22,13 +22,17 @@ $mdc-states-wash-duration: 15ms;
 $mdc-ripple-dark-ink-opacities: (
   hover: .04,
   focus: .12,
-  press: .16
+  press: .16,
+  selected: .04,
+  activated: .12
 ) !default;
 
 $mdc-ripple-light-ink-opacities: (
   hover: .08,
   focus: .24,
-  press: .32
+  press: .32,
+  selected: .08,
+  activated: .24
 ) !default;
 
 // Legacy