allow multiple style rules in a STYLE block of a webvtt file

PiperOrigin-RevId: 253959976

library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/CssParser.java

@@ -20,6 +20,8 @@ import android.text.TextUtils;
 import com.google.android.exoplayer2.util.ColorParser;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.Util;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -35,8 +37,8 @@ import java.util.regex.Pattern;
   private static final String PROPERTY_TEXT_DECORATION = "text-decoration";
   private static final String VALUE_BOLD = "bold";
   private static final String VALUE_UNDERLINE = "underline";
-  private static final String BLOCK_START = "{";
+  private static final String RULE_START = "{";
-  private static final String BLOCK_END = "}";
+  private static final String RULE_END = "}";
   private static final String PROPERTY_FONT_STYLE = "font-style";
   private static final String VALUE_ITALIC = "italic";
 
@@ -53,23 +55,26 @@ import java.util.regex.Pattern;
 
   /**
    * Takes a CSS style block and consumes up to the first empty line. Attempts to parse the contents
-   * of the style block and returns a {@link WebvttCssStyle} instance if successful, or {@code null}
+   * of the style block and returns a list of {@link WebvttCssStyle} instances if successful. If
-   * otherwise.
+   * parsing fails, it returns a list including only the styles which have been successfully parsed
+   * up to the style rule which was malformed.
    *
    * @param input The input from which the style block should be read.
-   * @return A {@link WebvttCssStyle} that represents the parsed block, or {@code null} if parsing
+   * @return A list of {@link WebvttCssStyle}s that represents the parsed block, or a list
-   *     failed.
+   *     containing the styles up to the parsing failure.
    */
-  @Nullable
+  public List<WebvttCssStyle> parseBlock(ParsableByteArray input) {
-  public WebvttCssStyle parseBlock(ParsableByteArray input) {
     stringBuilder.setLength(0);
     int initialInputPosition = input.getPosition();
     skipStyleBlock(input);
     styleInput.reset(input.data, input.getPosition());
     styleInput.setPosition(initialInputPosition);
-    String selector = parseSelector(styleInput, stringBuilder);
+
-    if (selector == null || !BLOCK_START.equals(parseNextToken(styleInput, stringBuilder))) {
+    List<WebvttCssStyle> styles = new ArrayList<>();
-      return null;
+    String selector;
+    while ((selector = parseSelector(styleInput, stringBuilder)) != null) {
+      if (!RULE_START.equals(parseNextToken(styleInput, stringBuilder))) {
+        return styles;
       }
       WebvttCssStyle style = new WebvttCssStyle();
       applySelectorToStyle(style, selector);
@@ -78,13 +83,18 @@ import java.util.regex.Pattern;
       while (!blockEndFound) {
         int position = styleInput.getPosition();
         token = parseNextToken(styleInput, stringBuilder);
-      blockEndFound = token == null || BLOCK_END.equals(token);
+        blockEndFound = token == null || RULE_END.equals(token);
         if (!blockEndFound) {
           styleInput.setPosition(position);
           parseStyleDeclaration(styleInput, style, stringBuilder);
         }
       }
-    return BLOCK_END.equals(token) ? style : null; // Check that the style block ended correctly.
+      // Check that the style rule ended correctly.
+      if (RULE_END.equals(token)) {
+        styles.add(style);
+      }
+    }
+    return styles;
   }
 
   /**
@@ -110,7 +120,7 @@ import java.util.regex.Pattern;
     if (token == null) {
       return null;
     }
-    if (BLOCK_START.equals(token)) {
+    if (RULE_START.equals(token)) {
       input.setPosition(position);
       return "";
     }
@@ -159,7 +169,7 @@ import java.util.regex.Pattern;
     String token = parseNextToken(input, stringBuilder);
     if (";".equals(token)) {
       // The style declaration is well formed.
-    } else if (BLOCK_END.equals(token)) {
+    } else if (RULE_END.equals(token)) {
       // The style declaration is well formed and we can go on, but the closing bracket had to be
       // fed back.
       input.setPosition(position);
@@ -255,7 +265,7 @@ import java.util.regex.Pattern;
         // Syntax error.
         return null;
       }
-      if (BLOCK_END.equals(token) || ";".equals(token)) {
+      if (RULE_END.equals(token) || ";".equals(token)) {
         input.setPosition(position);
         expressionEndFound = true;
       } else {

library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/WebvttDecoder.java

@@ -80,10 +80,7 @@ public final class WebvttDecoder extends SimpleSubtitleDecoder {
           throw new SubtitleDecoderException("A style block was found after the first cue.");
         }
         parsableWebvttData.readLine(); // Consume the "STYLE" header.
-        WebvttCssStyle styleBlock = cssParser.parseBlock(parsableWebvttData);
+        definedStyles.addAll(cssParser.parseBlock(parsableWebvttData));
-        if (styleBlock != null) {
-          definedStyles.add(styleBlock);
-        }
       } else if (event == EVENT_CUE) {
         if (cueParser.parseCue(parsableWebvttData, webvttCueBuilder, definedStyles)) {
           subtitles.add(webvttCueBuilder.build());

library/core/src/test/assets/webvtt/with_css_styles

@@ -13,8 +13,6 @@ STYLE
 ::cue(#id2) {
   color: peachpuff;
 }
-
-STYLE
 ::cue(v[voice="LaGord"]) { background-color: lime }
 
 STYLE

library/core/src/test/java/com/google/android/exoplayer2/text/webvtt/CssParserTest.java

@@ -21,6 +21,7 @@ import static com.google.common.truth.Truth.assertThat;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.Util;
+import java.util.List;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -87,21 +88,32 @@ public final class CssParserTest {
 
   @Test
   public void testParseMethodSimpleInput() {
-    String styleBlock1 = " ::cue { color : black; background-color: PapayaWhip }";
     WebvttCssStyle expectedStyle = new WebvttCssStyle();
+    String styleBlock1 = " ::cue { color : black; background-color: PapayaWhip }";
     expectedStyle.setFontColor(0xFF000000);
     expectedStyle.setBackgroundColor(0xFFFFEFD5);
-    assertParserProduces(expectedStyle, styleBlock1);
+    assertParserProduces(styleBlock1, expectedStyle);
 
     String styleBlock2 = " ::cue { color : black }\n\n::cue { color : invalid }";
     expectedStyle = new WebvttCssStyle();
     expectedStyle.setFontColor(0xFF000000);
-    assertParserProduces(expectedStyle, styleBlock2);
+    assertParserProduces(styleBlock2, expectedStyle);
 
-    String styleBlock3 = " \n::cue {\n background-color\n:#00fFFe}";
+    String styleBlock3 = "::cue {\n background-color\n:#00fFFe}";
     expectedStyle = new WebvttCssStyle();
     expectedStyle.setBackgroundColor(0xFF00FFFE);
-    assertParserProduces(expectedStyle, styleBlock3);
+    assertParserProduces(styleBlock3, expectedStyle);
+  }
+
+  @Test
+  public void testParseMethodMultipleRulesInBlockInput() {
+    String styleBlock =
+        "::cue {\n background-color\n:#00fFFe}      \n::cue {\n background-color\n:#00000000}\n";
+    WebvttCssStyle expectedStyle = new WebvttCssStyle();
+    expectedStyle.setBackgroundColor(0xFF00FFFE);
+    WebvttCssStyle secondExpectedStyle = new WebvttCssStyle();
+    secondExpectedStyle.setBackgroundColor(0x000000);
+    assertParserProduces(styleBlock, expectedStyle, secondExpectedStyle);
   }
 
   @Test
@@ -116,7 +128,7 @@ public final class CssParserTest {
     expectedStyle.setFontFamily("courier");
     expectedStyle.setBold(true);
 
-    assertParserProduces(expectedStyle, styleBlock);
+    assertParserProduces(styleBlock, expectedStyle);
   }
 
   @Test
@@ -128,7 +140,7 @@ public final class CssParserTest {
     expectedStyle.setBackgroundColor(0x190A0B0C);
     expectedStyle.setFontColor(0xFF010101);
 
-    assertParserProduces(expectedStyle, styleBlock);
+    assertParserProduces(styleBlock, expectedStyle);
   }
 
   @Test
@@ -203,10 +215,13 @@ public final class CssParserTest {
     assertThat(input.readLine()).isEqualTo(expectedLine);
   }
 
-  private void assertParserProduces(WebvttCssStyle expected,
+  private void assertParserProduces(String styleBlock, WebvttCssStyle... expectedStyles) {
-      String styleBlock){
     ParsableByteArray input = new ParsableByteArray(Util.getUtf8Bytes(styleBlock));
-    WebvttCssStyle actualElem = parser.parseBlock(input);
+    List<WebvttCssStyle> styles = parser.parseBlock(input);
+    assertThat(styles.size()).isEqualTo(expectedStyles.length);
+    for (int i = 0; i < expectedStyles.length; i++) {
+      WebvttCssStyle expected = expectedStyles[i];
+      WebvttCssStyle actualElem = styles.get(i);
       assertThat(actualElem.hasBackgroundColor()).isEqualTo(expected.hasBackgroundColor());
       if (expected.hasBackgroundColor()) {
         assertThat(actualElem.getBackgroundColor()).isEqualTo(expected.getBackgroundColor());
@@ -223,5 +238,6 @@ public final class CssParserTest {
       assertThat(actualElem.isUnderline()).isEqualTo(expected.isUnderline());
       assertThat(actualElem.getTextAlign()).isEqualTo(expected.getTextAlign());
     }
+  }
 
 }