Record the previous element that holds focus before the close button …

…is clicked and transfer focus to that element once the header is dismissed

kolibri/core/assets/src/views/CoreBanner.vue

@@ -31,6 +31,7 @@
         </KGridItem>
         <KGridItem v-else class="button-grid-item">
           <KButton
+            ref="close_button"
             class="close-button"
             :text="coreString('closeAction')"
             appearance="flat-button"
@@ -57,9 +58,22 @@
         bannerClosed: false,
       };
     },
+    created() {
+      document.addEventListener('focusin', this.focusChange);
+    },
+    beforeDestroy() {
+      document.removeEventListener('focusin', this.focusChange);
+    },
     methods: {
       toggleBanner() {
         this.bannerClosed = !this.bannerClosed;
+        this.previouslyFocusedElement.focus();
+      },
+      focusChange(e) {
+        // We need the element prior to the close button
+        if (this.$refs.close_button && e.target != this.$refs.close_button.$el) {
+          this.previouslyFocusedElement = e.target;
+        }
       },
     },
     $trs: {