fix: focus on first element when back to the settings menu (shaka-pro…

…ject#4653)

Going to the configuration menu using the keyboard and entering some
menu, when going back the focus is lost because the first element of the
HTML tree is hidden. This makes it difficult to use the player using
accessibility shortcuts.

Closes shaka-project#4652

Co-authored-by: Gonzalo Rodriguez <[email protected]>

ui/settings_menu.js

@@ -12,6 +12,7 @@ goog.require('shaka.ui.Enums');
 goog.require('shaka.ui.Utils');
 goog.require('shaka.util.Dom');
 goog.require('shaka.util.FakeEvent');
+goog.require('shaka.util.Iterables');
 goog.requireType('shaka.ui.Controls');
 
 
@@ -116,8 +117,16 @@ shaka.ui.SettingsMenu = class extends shaka.ui.Element {
       this.eventManager.listen(this.backButton, 'click', () => {
         shaka.ui.Utils.setDisplay(this.parent, true);
 
-        /** @type {!HTMLElement} */
-        (this.parent.childNodes[0]).focus();
+        const isDisplayed =
+        (element) => element.classList.contains('shaka-hidden') == false;
+
+        const Iterables = shaka.util.Iterables;
+        if (Iterables.some(this.parent.childNodes, isDisplayed)) {
+          // Focus on the first visible child of the overflow menu
+          const visibleElements =
+            Iterables.filter(this.parent.childNodes, isDisplayed);
+          /** @type {!HTMLElement} */ (visibleElements[0]).focus();
+        }
 
         // Make sure controls are displayed
         this.controls.computeOpacity();