Preserve Japanese language features when not applying embedded styling

Fix bug where rubies and boutens are missing, tate-chu-yoko is rendered
incorrectly when SubtitleView.setApplyEmbeddedStyles(false). This method
should only affect styling elements and not remove any language features.

library/ui/src/main/java/com/google/android/exoplayer2/ui/SubtitleView.java

@@ -386,7 +386,12 @@ public final class SubtitleView extends FrameLayout implements TextOutput {
           cue.buildUpon().setTextSize(Cue.DIMEN_UNSET, Cue.TYPE_UNSET).clearWindowColor();
       if (cueText != null) {
         // Remove all spans, regardless of type.
-        strippedCue.setText(cueText.toString());
+        strippedCue.setText(new SpannableString(cueText.toString()));
+        if (cueText instanceof Spanned) {
+          SubtitleViewUtils
+              .preserveJapaneseLanguageFeatures((SpannableString)strippedCue.getText(),
+                  (Spanned) cueText);
+        }
       }
       return strippedCue.build();
     } else if (!applyEmbeddedFontSizes) {

library/ui/src/main/java/com/google/android/exoplayer2/ui/SubtitleViewUtils.java

@@ -16,7 +16,13 @@
  */
 package com.google.android.exoplayer2.ui;
 
+import android.text.Spannable;
+import android.text.Spanned;
 import com.google.android.exoplayer2.text.Cue;
+import com.google.android.exoplayer2.text.span.HorizontalTextInVerticalContextSpan;
+import com.google.android.exoplayer2.text.span.RubySpan;
+import com.google.android.exoplayer2.text.span.SpanUtil;
+import com.google.android.exoplayer2.text.span.TextEmphasisSpan;
 
 /** Utility class for subtitle layout logic. */
 /* package */ final class SubtitleViewUtils {
@@ -48,5 +54,27 @@ import com.google.android.exoplayer2.text.Cue;
     }
   }
 
+  public static void preserveJapaneseLanguageFeatures(Spannable copy, Spanned original) {
+    RubySpan[] absSpans =
+        original.getSpans(0, original.length(), RubySpan.class);
+    for (RubySpan rubySpan : absSpans) {
+      SpanUtil.addOrReplaceSpan(copy, rubySpan, original.getSpanStart(rubySpan),
+          original.getSpanEnd(rubySpan), original.getSpanFlags(rubySpan));
+    }
+    TextEmphasisSpan[] textEmphasisSpans =
+        original.getSpans(0, original.length(), TextEmphasisSpan.class);
+    for (TextEmphasisSpan textEmphasisSpan : textEmphasisSpans) {
+      SpanUtil.addOrReplaceSpan(copy, textEmphasisSpan, original.getSpanStart(textEmphasisSpan),
+          original.getSpanEnd(textEmphasisSpan), original.getSpanFlags(textEmphasisSpan));
+    }
+    HorizontalTextInVerticalContextSpan[] horizontalTextInVerticalContextSpans =
+        original.getSpans(0, original.length(), HorizontalTextInVerticalContextSpan.class);
+
+    for (HorizontalTextInVerticalContextSpan span : horizontalTextInVerticalContextSpans) {
+      SpanUtil.addOrReplaceSpan(copy, span, original.getSpanStart(span),
+          original.getSpanEnd(span), original.getSpanFlags(span));
+    }
+  }
+
   private SubtitleViewUtils() {}
 }

library/ui/src/test/java/com/google/android/exoplayer2/ui/SubtitleViewUtilsTest.java

@@ -0,0 +1,63 @@
+package com.google.android.exoplayer2.ui;
+
+import static com.google.android.exoplayer2.testutil.truth.SpannedSubject.assertThat;
+
+import android.text.SpannableString;
+import android.text.Spanned;
+import android.text.style.UnderlineSpan;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.android.exoplayer2.text.span.HorizontalTextInVerticalContextSpan;
+import com.google.android.exoplayer2.text.span.RubySpan;
+import com.google.android.exoplayer2.text.span.TextAnnotation;
+import com.google.android.exoplayer2.text.span.TextEmphasisSpan;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(AndroidJUnit4.class)
+public class SubtitleViewUtilsTest {
+
+  @Test
+  public void testPreserveJapaneseLanguageFeatures() {
+    SpannableString spanned = new SpannableString("TextEmphasis おはよ Ruby ございます 123 Underline");
+    spanned.setSpan(
+        new TextEmphasisSpan(
+            TextEmphasisSpan.MARK_SHAPE_CIRCLE,
+            TextEmphasisSpan.MARK_FILL_FILLED,
+            TextAnnotation.POSITION_BEFORE),
+        "Text emphasis ".length(),
+        "Text emphasis おはよ".length(),
+        Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+
+    spanned.setSpan(
+        new RubySpan("おはよ", TextAnnotation.POSITION_BEFORE),
+        "TextEmphasis おはよ Ruby ".length(),
+        "TextEmphasis おはよ Ruby ございます".length(),
+        Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+
+    spanned.setSpan(
+        new HorizontalTextInVerticalContextSpan(),
+        "TextEmphasis おはよ Ruby ございます ".length(),
+        "TextEmphasis おはよ Ruby ございます 123".length(),
+        Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+
+    spanned.setSpan(
+        new UnderlineSpan(),
+        "TextEmphasis おはよ Ruby ございます 123".length(),
+        "TextEmphasis おはよ Ruby ございます 123 Underline".length(),
+        Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+
+    SpannableString spannable = new SpannableString(spanned.toString());
+    assertThat(spannable).hasNoTextEmphasisSpanBetween(0, spannable.length());
+
+    SubtitleViewUtils.preserveJapaneseLanguageFeatures(spannable, spanned);
+    assertThat(spannable)
+        .hasTextEmphasisSpanBetween("Text emphasis ".length(), "Text emphasis おはよ".length());
+    assertThat(spannable).hasRubySpanBetween("TextEmphasis おはよ Ruby ".length(),
+        "TextEmphasis おはよ Ruby ございます".length());
+    assertThat(spannable)
+        .hasHorizontalTextInVerticalContextSpanBetween("TextEmphasis おはよ Ruby ございます ".length(),
+            "TextEmphasis おはよ Ruby ございます 123".length());
+
+    assertThat(spannable).hasNoUnderlineSpanBetween(0, spannable.length());
+  }
+}