fix(UI): Fix visibility events while casting (#8574)

Author: avelad

ui/controls.js

@@ -142,7 +142,7 @@ shaka.ui.Controls = class extends shaka.util.FakeEventTarget {
       this.hideSettingsMenusTimer_.tickAfter(
           /* seconds= */ this.config_.closeMenusDelay);
 
-      this.dispatchEvent(new shaka.util.FakeEvent('hidingui'));
+      this.dispatchVisibilityEvent_();
     });
 
     /**
@@ -1591,7 +1591,7 @@ shaka.ui.Controls = class extends shaka.util.FakeEventTarget {
       this.updateTimeAndSeekRange_();
       this.computeOpacity();
 
-      this.dispatchEvent(new shaka.util.FakeEvent('showingui'));
+      this.dispatchVisibilityEvent_();
     }
 
     // Hide the cursor when the mouse stops moving.
@@ -1740,6 +1740,7 @@ shaka.ui.Controls = class extends shaka.util.FakeEventTarget {
     } else {
       this.controlsContainer_.removeAttribute('casting');
     }
+    this.dispatchVisibilityEvent_();
   }
 
   /** @private */
@@ -1885,6 +1886,17 @@ shaka.ui.Controls = class extends shaka.util.FakeEventTarget {
         this.controlsContainer_.getAttribute('casting') != null;
   }
 
+  /**
+   * @private
+   */
+  dispatchVisibilityEvent_() {
+    if (this.isOpaque()) {
+      this.dispatchEvent(new shaka.util.FakeEvent('showingui'));
+    } else {
+      this.dispatchEvent(new shaka.util.FakeEvent('hidingui'));
+    }
+  }
+
   /**
    * Update the video's current time based on the keyboard operations.
    *