refactor(material/button): handle disabled state of icon buttons through tokens

* Fixes that icon buttons weren't using the right token for disabled state.
* Fixes that the specificity of the icon button disabled styles was really high.
* Moves the logic for generating the palette tokens into the icon button tokens file.
* Fixes one place where we were referencing a token directly instead of using the API to generate the name.

Author: crisbeto

src/dev-app/button/button-demo.html

@@ -150,6 +150,25 @@ <h4 class="demo-section-header"> Icon Buttons [mat-icon-button]</h4>
     </button>
   </section>
 
+  <h4 class="demo-section-header"> Icon Button Anchors [mat-icon-button]</h4>
+  <section>
+    <a href="#" mat-icon-button>
+      <mat-icon>cached</mat-icon>
+    </a>
+    <a href="#" mat-icon-button color="primary">
+      <mat-icon>cached</mat-icon>
+    </a>
+    <a href="#" mat-icon-button color="accent">
+      <mat-icon>backup</mat-icon>
+    </a>
+    <a href="#" mat-icon-button color="warn">
+      <mat-icon>trending_up</mat-icon>
+    </a>
+    <a href="#" mat-icon-button disabled>
+      <mat-icon>visibility</mat-icon>
+    </a>
+  </section>
+
   <h4 class="demo-section-header">Fab Buttons [mat-fab]</h4>
   <section>
     <button mat-fab>

src/material/button/_icon-button-theme.scss

@@ -1,7 +1,6 @@
 @use 'sass:math';
 @use '@material/density/functions' as mdc-density-functions;
 @use '@material/icon-button/icon-button-theme' as mdc-icon-button-theme;
-@use '@material/theme/theme-color' as mdc-theme-color;
 @use '../core/tokens/m2/mdc/icon-button' as tokens-mdc-icon-button;
 
 @use './button-theme-private';
@@ -10,64 +9,46 @@
 
 $_icon-size: 24px;
 
+// TODO(crisbeto): move these into tokens
 @mixin _ripple-color($color) {
   --mat-mdc-button-persistent-ripple-color: #{$color};
   --mat-mdc-button-ripple-color: #{rgba($color, 0.1)};
 }
 
-@function _variable-safe-contrast-tone($value, $is-dark) {
-  @if ($value == 'dark' or $value == 'light' or type-of($value) == 'color') {
-    @return mdc-theme-color.contrast-tone($value);
-  }
-
-  @return if($is-dark, 'light', 'dark');
-}
-
 @mixin base($theme) {
   // TODO(mmalerba): Move icon button base tokens here
 }
 
 @mixin color($theme) {
   $color-tokens: tokens-mdc-icon-button.get-color-tokens($theme);
-  $surface: inspection.get-theme-color($theme, background, card);
   $is-dark: inspection.get-theme-type($theme) == dark;
-  $on-surface: if(_variable-safe-contrast-tone($surface, $is-dark) == 'dark', #000, #fff);
 
   .mat-mdc-icon-button {
     @include button-theme-private.ripple-theme-styles($theme, false);
     @include mdc-icon-button-theme.theme($color-tokens);
-    @include _ripple-color($on-surface);
+    @include _ripple-color(if($is-dark, #fff, #000));
 
     &.mat-primary {
-      $color: inspection.get-theme-color($theme, primary);
-      @include mdc-icon-button-theme.theme((icon-color: $color));
-      @include _ripple-color($color);
+      @include _ripple-color(inspection.get-theme-color($theme, primary));
+      @include mdc-icon-button-theme.theme(
+        tokens-mdc-icon-button.private-get-color-palette-color-tokens($theme, primary));
     }
 
     &.mat-accent {
-      $color: inspection.get-theme-color($theme, accent);
-      @include mdc-icon-button-theme.theme((icon-color: $color));
-      @include _ripple-color($color);
+      @include _ripple-color(inspection.get-theme-color($theme, accent));
+      @include mdc-icon-button-theme.theme(
+        tokens-mdc-icon-button.private-get-color-palette-color-tokens($theme, accent));
     }
 
     &.mat-warn {
-      $color: inspection.get-theme-color($theme, warn);
-      @include mdc-icon-button-theme.theme((icon-color: $color));
-      @include _ripple-color($color);
-    }
-
-    @include button-theme-private.apply-disabled-style() {
-      $disabled-color: rgba($on-surface, if($is-dark, 0.5, 0.38));
-      @include mdc-icon-button-theme.theme((
-        icon-color: $disabled-color,
-        disabled-icon-color: $disabled-color,
-      ));
+      @include _ripple-color(inspection.get-theme-color($theme, warn));
+      @include mdc-icon-button-theme.theme(
+        tokens-mdc-icon-button.private-get-color-palette-color-tokens($theme, warn));
     }
   }
 }
 
-@mixin typography($theme) {
-}
+@mixin typography($theme) {}
 
 @mixin density($theme) {
   $density-scale: inspection.get-theme-density($theme);

src/material/button/icon-button.scss

@@ -2,14 +2,15 @@
 @use '@material/icon-button/icon-button-theme' as mdc-icon-button-theme;
 @use '@material/theme/custom-properties' as mdc-custom-properties;
 
-@use '../core/tokens/m2/mdc/icon-button' as m2-mdc-icon-button;
+@use '../core/tokens/m2/mdc/icon-button' as tokens-mdc-icon-button;
 
 @use './button-base';
 @use '../core/style/private';
+@use '../core/tokens/token-utils';
 
 // The slots for tokens that will be configured in the theme can be emitted with no fallback.
 @include mdc-custom-properties.configure($emit-fallback-values: false, $emit-fallback-vars: false) {
-  $token-slots: m2-mdc-icon-button.get-token-slots();
+  $token-slots: tokens-mdc-icon-button.get-token-slots();
 
   // Add the MDC component static styles.
   @include mdc-icon-button.static-styles();
@@ -28,10 +29,6 @@
   // TODO: Determine how to enforce theming exists, otherwise padding will be unset.
   padding: 12px;
 
-  // Icon size used to be placed on the host element. Now, in `theme-styles` it is placed on
-  // the unused `.mdc-button__icon` class. Explicitly set the font-size here.
-  font-size: var(--mdc-icon-button-icon-size);
-
   // Border radius is inherited by ripple to know its shape. Set to 50% so the ripple is round.
   border-radius: 50%;
 
@@ -45,11 +42,18 @@
     vertical-align: baseline;
   }
 
-  @include button-base.mat-private-button-disabled() {
-    // The color is already dimmed when the button is disabled. Restore the opacity both to
-    // help with the color contrast and to align with what we had before switching to the new API.
-    opacity: 1;
-  };
+  @include token-utils.use-tokens(
+    tokens-mdc-icon-button.$prefix, tokens-mdc-icon-button.get-token-slots()) {
+    // Icon size used to be placed on the host element. Now, in `theme-styles` it is placed on
+    // the unused `.mdc-button__icon` class. Explicitly set the font-size here.
+    @include token-utils.create-token-slot(font-size, icon-size);
+
+    @include button-base.mat-private-button-disabled {
+      // MDC's disabled styles target the `:disabled` selector which doesn't work on links.
+      // We re-apply the disabled icon color here since we support Material buttons on links too.
+      @include token-utils.create-token-slot(color, disabled-icon-color);
+    };
+  }
 
   @include button-base.mat-private-button-interactive();
   @include button-base.mat-private-button-touch-target(true);

src/material/core/tokens/m2/mdc/_icon-button.scss

@@ -1,4 +1,6 @@
+@use 'sass:map';
 @use '../../../style/sass-utils';
+@use '../../../theming/inspection';
 @use '../../token-utils';
 
 // The prefix used to generate the fully qualified name for tokens in this file.
@@ -20,12 +22,7 @@ $prefix: (mdc, icon-button);
     state-layer-size: 48px,
     // MDC's icon size applied to svg and img elements inside the component
     icon-size: 24px,
-    // Only applies to :disabled icons, but Angular Components uses [disabled] since :disabled
-    // wouldn't work on <a> tags.
-    disabled-icon-color: black,
-    // Angular version applies an opacity 1 with a color change, and this only applies with
-    // :disabled anyways.
-    disabled-icon-opacity: 0.38,
+
     // =============================================================================================
     // = TOKENS NOT USED IN ANGULAR MATERIAL                                                       =
     // =============================================================================================
@@ -41,13 +38,29 @@ $prefix: (mdc, icon-button);
     pressed-state-layer-opacity: null,
     focus-ring-color: null,
     focus-ring-offset: null,
+
+    // We use a color with an opacity to show the disabled state,
+    // instead of applying it to the entire button.
+    disabled-icon-opacity: null,
   );
 }
 
 // Tokens that can be configured through Angular Material's color theming API.
 @function get-color-tokens($theme) {
+  $is-dark: inspection.get-theme-type($theme) == dark;
+
   @return (
     icon-color: inherit,
+    disabled-icon-color: if($is-dark, rgba(#fff, 0.5), rgba(#000, 0.38)),
+  );
+}
+
+// Generates the mapping for the properties that change based on the button palette color.
+@function private-get-color-palette-color-tokens($theme, $palette-name) {
+  $palette: map.get($theme, $palette-name);
+
+  @return (
+    icon-color: inspection.get-theme-color($theme, $palette-name)
   );
 }