fix: Prefer SimpleTextDisplayer on iOS

demo/main.js

@@ -1347,8 +1347,16 @@ shakaDemo.Main = class {
       } else {
         this.controls_.setEnabledShakaControls(true);
         this.controls_.setEnabledNativeControls(false);
-        // This will force the player to use UITextDisplayer.
-        this.player_.setVideoContainer(this.container_);
+        // On devices where the Fullscreen API is not available we prefer
+        // SimpleTextDisplayer because it works with the Fullscreen API
+        // of the video element itself.
+        if (document.fullscreenEnabled) {
+          // This will force the player to use UITextDisplayer.
+          this.player_.setVideoContainer(this.container_);
+        } else {
+          // This will force the player to use SimpleTextDisplayer.
+          this.player_.setVideoContainer(null);
+        }
       }
 
       await this.drmConfiguration_(asset);

lib/text/ui_text_displayer.js

@@ -9,6 +9,7 @@ goog.provide('shaka.text.UITextDisplayer');
 
 goog.require('goog.asserts');
 goog.require('shaka.Deprecate');
+goog.require('shaka.log');
 goog.require('shaka.text.Cue');
 goog.require('shaka.text.CueRegion');
 goog.require('shaka.text.Utils');
@@ -35,6 +36,12 @@ shaka.text.UITextDisplayer = class {
   constructor(video, videoContainer, config) {
     goog.asserts.assert(videoContainer, 'videoContainer should be valid.');
 
+    if (!document.fullscreenEnabled) {
+      shaka.log.alwaysWarn('Using UITextDisplayer in a browser without ' +
+          'Fullscreen API support causes subtitles to not be rendered in ' +
+          'fullscreen');
+    }
+
     /** @private {boolean} */
     this.isTextVisible_ = false;