79730: Keyboard navigation for expandable filter facets

src/app/shared/search/search-filters/search-filter/search-filter.component.html

@@ -1,17 +1,19 @@
-<div class="facet-filter d-block mb-3 p-3" *ngIf="active$ | async">
-  <div (click)="toggle()" class="filter-name">
+<div class="facet-filter d-block mb-3 p-3" *ngIf="active$ | async"
+     [id]="regionId" [attr.aria-labelledby]="toggleId" [ngClass]="{ 'focus': focusBox }" role="region">
+  <button (click)="toggle()" (focusin)="focusBox = true" (focusout)="focusBox = false"
+          class="filter-name d-flex" [attr.aria-controls]="regionId" [id]="toggleId" [attr.aria-expanded]="false">
     <h5 class="d-inline-block mb-0">
       {{'search.filters.filter.' + filter.name + '.head'| translate}}
     </h5>
-    <span class="filter-toggle fas float-right"
+    <span class="filter-toggle flex-grow-1 fas p-auto"
           [ngClass]="(collapsed$ | async) ? 'fa-plus' : 'fa-minus'"
           [title]="((collapsed$ | async) ? 'search.filters.filter.expand' : 'search.filters.filter.collapse') | translate"
           [attr.aria-label]="((collapsed$ | async) ? 'search.filters.filter.expand' : 'search.filters.filter.collapse') | translate">
     </span>
-  </div>
+  </button>
   <div [@slide]="(collapsed$ | async) ? 'collapsed' : 'expanded'"
        (@slide.start)="startSlide($event)" (@slide.done)="finishSlide($event)"
-       class="search-filter-wrapper" [ngClass]="{'closed' : closed}">
+       class="search-filter-wrapper" [ngClass]="{ 'closed' : closed, 'notab': notab }">
     <ds-search-facet-filter-wrapper
       [filterConfig]="filter"
       [inPlaceSearch]="inPlaceSearch">

src/app/shared/search/search-filters/search-filter/search-filter.component.scss

@@ -1,10 +1,36 @@
 :host .facet-filter {
   border: 1px solid var(--bs-light);
   cursor: pointer;
-    .search-filter-wrapper.closed {
+  line-height: 0;
+
+  .search-filter-wrapper {
+    line-height: var(--bs-line-height-base);
+    &.closed {
       overflow: hidden;
     }
+    &.notab {
+      visibility: hidden;
+    }
+  }
+
   .filter-toggle {
     line-height: var(--bs-line-height-base);
+    text-align: right;
+    position: relative;
+    top: -0.125rem;           // Fix weird outline shape in Chrome
+  }
+
+  > button {
+    appearance: none;
+    border: 0;
+    padding: 0;
+    background: transparent;
+    width: 100%;
+    outline: none !important;
+  }
+
+  &.focus {
+    outline: none;
+    box-shadow: var(--bs-input-btn-focus-box-shadow);
   }
 }

src/app/shared/search/search-filters/search-filter/search-filter.component.ts

@@ -37,6 +37,16 @@ export class SearchFilterComponent implements OnInit {
    */
   closed: boolean;
 
+  /**
+   * True when the filter controls should be hidden & removed from the tablist
+   */
+  notab: boolean;
+
+  /**
+   * True when the filter toggle button is focused
+   */
+  focusBox: boolean = false;
+
   /**
    * Emits true when the filter is currently collapsed in the store
    */
@@ -112,6 +122,9 @@ export class SearchFilterComponent implements OnInit {
     if (event.fromState === 'collapsed') {
       this.closed = false;
     }
+    if (event.toState === 'collapsed') {
+      this.notab = true;
+    }
   }
 
   /**
@@ -122,6 +135,17 @@ export class SearchFilterComponent implements OnInit {
     if (event.toState === 'collapsed') {
       this.closed = true;
     }
+    if (event.fromState === 'collapsed') {
+      this.notab = false;
+    }
+  }
+
+  get regionId(): string {
+    return `search-filter-region-${this.constructor['ɵcmp'].id}`;
+  }
+
+  get toggleId(): string {
+    return `search-filter-toggle-${this.constructor['ɵcmp'].id}`;
   }
 
   /**