Stop parsing unsupported WebVTT CSS properties

The spec lists an exhaustive list of CSS properties that should be
recognised, all others must be ignored:
https://www.w3.org/TR/webvtt1/#the-cue-pseudo-element

PiperOrigin-RevId: 310353888

RELEASENOTES.md

@@ -116,6 +116,9 @@
         horizontally.
     *   Implement steps 4-10 of the
         [WebVTT line computation algorithm](https://www.w3.org/TR/webvtt1/#cue-computed-line).
+    *   Stop parsing unsupported WebVTT CSS properties. The spec provides an
+        [exhaustive list](https://www.w3.org/TR/webvtt1/#the-cue-pseudo-element)
+        of which are supported.
 *   DRM:
     *   Add support for attaching DRM sessions to clear content in the demo app.
     *   Remove `DrmSessionManager` references from all renderers.

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

@@ -36,7 +36,7 @@ import java.util.regex.Pattern;
 
   private static final String RULE_START = "{";
   private static final String RULE_END = "}";
-  private static final String PROPERTY_BGCOLOR = "background-color";
+  private static final String PROPERTY_COLOR = "color";
   private static final String PROPERTY_FONT_FAMILY = "font-family";
   private static final String PROPERTY_FONT_WEIGHT = "font-weight";
   private static final String PROPERTY_TEXT_COMBINE_UPRIGHT = "text-combine-upright";
@@ -184,10 +184,8 @@ import java.util.regex.Pattern;
       return;
     }
     // At this point we have a presumably valid declaration, we need to parse it and fill the style.
-    if ("color".equals(property)) {
+    if (PROPERTY_COLOR.equals(property)) {
       style.setFontColor(ColorParser.parseCssColor(value));
-    } else if (PROPERTY_BGCOLOR.equals(property)) {
-      style.setBackgroundColor(ColorParser.parseCssColor(value));
     } else if (PROPERTY_TEXT_COMBINE_UPRIGHT.equals(property)) {
       style.setCombineUpright(VALUE_ALL.equals(value) || value.startsWith(VALUE_DIGITS));
     } else if (PROPERTY_TEXT_DECORATION.equals(property)) {

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

@@ -16,7 +16,6 @@
 package com.google.android.exoplayer2.text.webvtt;
 
 import android.graphics.Typeface;
-import android.text.Layout;
 import android.text.TextUtils;
 import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
@@ -86,15 +85,12 @@ public final class WebvttCssStyle {
   @Nullable private String fontFamily;
   private int fontColor;
   private boolean hasFontColor;
-  private int backgroundColor;
-  private boolean hasBackgroundColor;
   @OptionalBoolean private int linethrough;
   @OptionalBoolean private int underline;
   @OptionalBoolean private int bold;
   @OptionalBoolean private int italic;
   @FontSizeUnit private int fontSizeUnit;
   private float fontSize;
-  @Nullable private Layout.Alignment textAlign;
   private boolean combineUpright;
 
   // Calling reset() is forbidden because `this` isn't initialized. This can be safely suppressed
@@ -112,13 +108,11 @@ public final class WebvttCssStyle {
     targetVoice = "";
     fontFamily = null;
     hasFontColor = false;
-    hasBackgroundColor = false;
     linethrough = UNSPECIFIED;
     underline = UNSPECIFIED;
     bold = UNSPECIFIED;
     italic = UNSPECIFIED;
     fontSizeUnit = UNSPECIFIED;
-    textAlign = null;
     combineUpright = false;
   }
 
@@ -244,33 +238,6 @@ public final class WebvttCssStyle {
     return hasFontColor;
   }
 
-  public int getBackgroundColor() {
-    if (!hasBackgroundColor) {
-      throw new IllegalStateException("Background color not defined.");
-    }
-    return backgroundColor;
-  }
-
-  public WebvttCssStyle setBackgroundColor(int backgroundColor) {
-    this.backgroundColor = backgroundColor;
-    hasBackgroundColor = true;
-    return this;
-  }
-
-  public boolean hasBackgroundColor() {
-    return hasBackgroundColor;
-  }
-
-  @Nullable
-  public Layout.Alignment getTextAlign() {
-    return textAlign;
-  }
-
-  public WebvttCssStyle setTextAlign(@Nullable Layout.Alignment textAlign) {
-    this.textAlign = textAlign;
-    return this;
-  }
-
   public WebvttCssStyle setFontSize(float fontSize) {
     this.fontSize = fontSize;
     return this;

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

@@ -26,7 +26,6 @@ import android.text.Spanned;
 import android.text.SpannedString;
 import android.text.TextUtils;
 import android.text.style.AbsoluteSizeSpan;
-import android.text.style.AlignmentSpan;
 import android.text.style.BackgroundColorSpan;
 import android.text.style.ForegroundColorSpan;
 import android.text.style.RelativeSizeSpan;
@@ -647,14 +646,6 @@ public final class WebvttCueParser {
           end,
           Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
     }
-    if (style.hasBackgroundColor()) {
-      addOrReplaceSpan(
-          spannedText,
-          new BackgroundColorSpan(style.getBackgroundColor()),
-          start,
-          end,
-          Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
-    }
     if (style.getFontFamily() != null) {
       addOrReplaceSpan(
           spannedText,
@@ -663,15 +654,6 @@ public final class WebvttCueParser {
           end,
           Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
     }
-    Layout.Alignment textAlign = style.getTextAlign();
-    if (textAlign != null) {
-      addOrReplaceSpan(
-          spannedText,
-          new AlignmentSpan.Standard(textAlign),
-          start,
-          end,
-          Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
-    }
     switch (style.getFontSizeUnit()) {
       case WebvttCssStyle.FONT_SIZE_UNIT_PIXEL:
         addOrReplaceSpan(

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

@@ -89,41 +89,33 @@ public final class CssParserTest {
   @Test
   public void parseMethodSimpleInput() {
     WebvttCssStyle expectedStyle = new WebvttCssStyle();
-    String styleBlock1 = " ::cue { color : black; background-color: PapayaWhip }";
-    expectedStyle.setFontColor(0xFF000000);
-    expectedStyle.setBackgroundColor(0xFFFFEFD5);
+    String styleBlock1 = " ::cue { color : PapayaWhip }";
+    expectedStyle.setFontColor(0xFFFFEFD5);
     assertParserProduces(styleBlock1, expectedStyle);
 
     String styleBlock2 = " ::cue { color : black }\n\n::cue { color : invalid }";
     expectedStyle = new WebvttCssStyle();
     expectedStyle.setFontColor(0xFF000000);
     assertParserProduces(styleBlock2, expectedStyle);
-
-    String styleBlock3 = "::cue {\n background-color\n:#00fFFe}";
-    expectedStyle = new WebvttCssStyle();
-    expectedStyle.setBackgroundColor(0xFF00FFFE);
-    assertParserProduces(styleBlock3, expectedStyle);
   }
 
   @Test
   public void parseMethodMultipleRulesInBlockInput() {
-    String styleBlock =
-        "::cue {\n background-color\n:#00fFFe}      \n::cue {\n background-color\n:#00000000}\n";
+    String styleBlock = "::cue {\n color\n:#00fFFe}      \n::cue {\n color\n:#00000000}\n";
     WebvttCssStyle expectedStyle = new WebvttCssStyle();
-    expectedStyle.setBackgroundColor(0xFF00FFFE);
+    expectedStyle.setFontColor(0xFF00FFFE);
     WebvttCssStyle secondExpectedStyle = new WebvttCssStyle();
-    secondExpectedStyle.setBackgroundColor(0x000000);
+    secondExpectedStyle.setFontColor(0x000000);
     assertParserProduces(styleBlock, expectedStyle, secondExpectedStyle);
   }
 
   @Test
   public void multiplePropertiesInBlock() {
-    String styleBlock = "::cue(#id){text-decoration:underline; background-color:green;"
-        + "color:red; font-family:Courier; font-weight:bold}";
+    String styleBlock =
+        "::cue(#id){text-decoration:underline; color:red; font-family:Courier; font-weight:bold}";
     WebvttCssStyle expectedStyle = new WebvttCssStyle();
     expectedStyle.setTargetId("id");
     expectedStyle.setUnderline(true);
-    expectedStyle.setBackgroundColor(0xFF008000);
     expectedStyle.setFontColor(0xFFFF0000);
     expectedStyle.setFontFamily("courier");
     expectedStyle.setBold(true);
@@ -133,12 +125,10 @@ public final class CssParserTest {
 
   @Test
   public void rgbaColorExpression() {
-    String styleBlock = "::cue(#rgb){background-color: rgba(\n10/* Ugly color */,11\t, 12\n,.1);"
-        + "color:rgb(1,1,\n1)}";
+    String styleBlock = "::cue(#rgb){color: rgba(\n10/* Ugly color */,11\t, 12\n,.1);}";
     WebvttCssStyle expectedStyle = new WebvttCssStyle();
     expectedStyle.setTargetId("rgb");
-    expectedStyle.setBackgroundColor(0x190A0B0C);
-    expectedStyle.setFontColor(0xFF010101);
+    expectedStyle.setFontColor(0x190A0B0C);
 
     assertParserProduces(styleBlock, expectedStyle);
   }
@@ -222,10 +212,6 @@ public final class CssParserTest {
     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());
-      }
       assertThat(actualElem.hasFontColor()).isEqualTo(expected.hasFontColor());
       if (expected.hasFontColor()) {
         assertThat(actualElem.getFontColor()).isEqualTo(expected.getFontColor());
@@ -236,7 +222,6 @@ public final class CssParserTest {
       assertThat(actualElem.getStyle()).isEqualTo(expected.getStyle());
       assertThat(actualElem.isLinethrough()).isEqualTo(expected.isLinethrough());
       assertThat(actualElem.isUnderline()).isEqualTo(expected.isUnderline());
-      assertThat(actualElem.getTextAlign()).isEqualTo(expected.getTextAlign());
     }
   }
 

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

@@ -371,9 +371,6 @@ public class WebvttDecoderTest {
     assertThat(firstCueText)
         .hasForegroundColorSpanBetween(0, firstCueText.length())
         .withColor(ColorParser.parseCssColor("papayawhip"));
-    assertThat(firstCueText)
-        .hasBackgroundColorSpanBetween(0, firstCueText.length())
-        .withColor(ColorParser.parseCssColor("green"));
 
     Spanned secondCueText = getUniqueSpanTextAt(subtitle, 2_345_000);
     assertThat(secondCueText.toString()).isEqualTo("This is the second subtitle.");
@@ -388,7 +385,7 @@ public class WebvttDecoderTest {
     Spanned fourthCueText = getUniqueSpanTextAt(subtitle, 25_000_000);
     assertThat(fourthCueText.toString()).isEqualTo("You are an idiot\nYou don't have the guts");
     assertThat(fourthCueText)
-        .hasBackgroundColorSpanBetween(0, "You are an idiot".length())
+        .hasForegroundColorSpanBetween(0, "You are an idiot".length())
         .withColor(ColorParser.parseCssColor("lime"));
     assertThat(fourthCueText)
         .hasBoldSpanBetween("You are an idiot\n".length(), fourthCueText.length());

testdata/src/test/assets/webvtt/with_css_styles

@@ -2,7 +2,6 @@ WEBVTT
 
 STYLE
 ::cue {
-  background-color: green;
   color: papayawhip;
 }
 /* Style blocks cannot use blank lines nor "dash dash greater than" */
@@ -13,7 +12,7 @@ STYLE
 ::cue(#id2) {
   color: peachpuff;
 }
-::cue(v[voice="LaGord"]) { background-color: lime }
+::cue(v[voice="LaGord"]) { color: lime }
 
 STYLE
 ::cue(v[voice="The Frog"]) { font-weight: bold }