Add support for font size in SSA v4+ styling.

demos/main/src/main/assets/media.exolist.json

@@ -506,6 +506,13 @@
         "subtitle_mime_type": "text/x-ssa",
         "subtitle_language": "en"
       },
+      {
+        "name": "SubStation Alpha font size",
+        "uri": "https://storage.googleapis.com/exoplayer-test-media-1/gen-3/screens/dash-vod-single-segment/video-avc-baseline-480.mp4",
+        "subtitle_uri": "https://drive.google.com/uc?export=download&id=13EdW4Qru-vQerUlwS_Ht5Cely_Tn0tQe",
+        "subtitle_mime_type": "text/x-ssa",
+        "subtitle_language": "en"
+      },
       {
         "name": "MPEG-4 Timed Text",
         "uri": "https://storage.googleapis.com/exoplayer-test-media-1/mp4/dizzy-with-tx3g.mp4"

library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDecoder.java

@@ -314,6 +314,11 @@ public final class SsaDecoder extends SimpleSubtitleDecoder {
             /* end= */ spannableText.length(),
             SpannableString.SPAN_EXCLUSIVE_EXCLUSIVE);
       }
+      if (style.fontSize != null && screenHeight != Cue.DIMEN_UNSET) {
+        cue.setTextSize(
+            style.fontSize / screenHeight,
+            Cue.TEXT_SIZE_TYPE_FRACTIONAL_IGNORE_PADDING);
+      }
     }
 
     @SsaStyle.SsaAlignment int alignment;

library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaStyle.java

@@ -90,12 +90,17 @@ import java.util.regex.Pattern;
   public final String name;
   @SsaAlignment public final int alignment;
   @Nullable @ColorInt public final Integer primaryColor;
+  public final Integer fontSize;
 
   private SsaStyle(
-      String name, @SsaAlignment int alignment, @Nullable @ColorInt Integer primaryColor) {
+      String name,
+      @SsaAlignment int alignment,
+      @Nullable @ColorInt Integer primaryColor,
+      Integer fontSize) {
     this.name = name;
     this.alignment = alignment;
     this.primaryColor = primaryColor;
+    this.fontSize = fontSize;
   }
 
   @Nullable
@@ -114,7 +119,8 @@ import java.util.regex.Pattern;
       return new SsaStyle(
           styleValues[format.nameIndex].trim(),
           parseAlignment(styleValues[format.alignmentIndex].trim()),
-          parseColor(styleValues[format.primaryColorIndex].trim()));
+          parseColor(styleValues[format.primaryColorIndex].trim()),
+          parseFontSize(styleValues[format.fontSizeIndex].trim()));
     } catch (RuntimeException e) {
       Log.w(TAG, "Skipping malformed 'Style:' line: '" + styleLine + "'", e);
       return null;
@@ -191,6 +197,15 @@ import java.util.regex.Pattern;
     return Color.argb(a, r, g, b);
   }
 
+  private static Integer parseFontSize(String fontSize) {
+    try {
+      return Integer.parseInt(fontSize);
+    } catch (NumberFormatException e) {
+      Log.w(TAG, "Failed to parse font size: '" + fontSize + "'", e);
+      return null;
+    }
+  }
+
   /**
    * Represents a {@code Format:} line from the {@code [V4+ Styles]} section
    *
@@ -202,12 +217,19 @@ import java.util.regex.Pattern;
     public final int nameIndex;
     public final int alignmentIndex;
     public final int primaryColorIndex;
+    public final int fontSizeIndex;
     public final int length;
 
-    private Format(int nameIndex, int alignmentIndex, int primaryColorIndex, int length) {
+    private Format(
+        int nameIndex,
+        int alignmentIndex,
+        int primaryColorIndex,
+        int fontSizeIndex,
+        int length) {
       this.nameIndex = nameIndex;
       this.alignmentIndex = alignmentIndex;
       this.primaryColorIndex = primaryColorIndex;
+      this.fontSizeIndex = fontSizeIndex;
       this.length = length;
     }
 
@@ -221,6 +243,7 @@ import java.util.regex.Pattern;
       int nameIndex = C.INDEX_UNSET;
       int alignmentIndex = C.INDEX_UNSET;
       int primaryColorIndex = C.INDEX_UNSET;
+      int fontSizeIndex = C.INDEX_UNSET;
       String[] keys =
           TextUtils.split(styleFormatLine.substring(SsaDecoder.FORMAT_LINE_PREFIX.length()), ",");
       for (int i = 0; i < keys.length; i++) {
@@ -234,10 +257,13 @@ import java.util.regex.Pattern;
           case "primarycolour":
             primaryColorIndex = i;
             break;
+          case "fontsize":
+            fontSizeIndex = i;
+            break;
         }
       }
       return nameIndex != C.INDEX_UNSET
-          ? new Format(nameIndex, alignmentIndex, primaryColorIndex, keys.length)
+          ? new Format(nameIndex, alignmentIndex, primaryColorIndex, fontSizeIndex, keys.length)
           : null;
     }
   }