Filter Alias which points non-existing font family name

The FontFamily will be removed if none of font files exist on the
device.

Bug: 192479819
Test: atest FontListParserTest
Change-Id: I36f6476fe37bc04ec8737936747385c63908d651
(cherry picked from commit 691cfe8818513e576300cdb963a65341984659c4)

core/tests/coretests/src/android/graphics/FontListParserTest.java

@@ -27,6 +27,7 @@ import static com.google.common.truth.Truth.assertThat;
 
 import static junit.framework.Assert.fail;
 
+import android.graphics.fonts.FontCustomizationParser;
 import android.graphics.fonts.FontStyle;
 import android.os.LocaleList;
 import android.text.FontConfig;
@@ -46,6 +47,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
+import java.util.List;
 
 @SmallTest
 @RunWith(AndroidJUnit4.class)
@@ -318,6 +320,52 @@ public final class FontListParserTest {
         }
     }
 
+    @Test
+    public void alias() throws Exception {
+        String xml = "<?xml version='1.0' encoding='UTF-8'?>"
+                + "<familyset>"
+                + "  <family name='sans-serif'>"
+                + "    <font>test.ttf</font>"
+                + "  </family>"
+                + "  <family name='custom-family'>"
+                + "    <font>missing.ttf</font>"
+                + "  </family>"
+                + "  <alias name='custom-alias' to='sans-serif'/>"
+                + "</familyset>";
+        FontConfig config = readFamilies(xml, true /* include non-existing font files */);
+        List<FontConfig.Alias> aliases = config.getAliases();
+        assertThat(aliases.size()).isEqualTo(1);
+        assertThat(aliases.get(0).getName()).isEqualTo("custom-alias");
+        assertThat(aliases.get(0).getOriginal()).isEqualTo("sans-serif");
+    }
+
+    @Test
+    public void dropped_FamilyAlias() throws Exception {
+        String xml = "<?xml version='1.0' encoding='UTF-8'?>"
+                + "<familyset>"
+                + "  <family name='sans-serif'>"
+                + "    <font>test.ttf</font>"
+                + "  </family>"
+                + "  <family name='custom-family'>"
+                + "    <font>missing.ttf</font>"
+                + "  </family>"
+                + "  <alias name='custom-alias' to='custom-family'/>"
+                + "</familyset>";
+        FontConfig config = readFamilies(xml, false /* exclude not existing file */);
+        assertThat(config.getAliases()).isEmpty();
+    }
+
+    private FontConfig readFamilies(String xml, boolean allowNonExisting)
+            throws IOException, XmlPullParserException {
+        ByteArrayInputStream buffer = new ByteArrayInputStream(
+                xml.getBytes(StandardCharsets.UTF_8));
+        XmlPullParser parser = Xml.newPullParser();
+        parser.setInput(buffer, "UTF-8");
+        parser.nextTag();
+        return FontListParser.readFamilies(parser, "", new FontCustomizationParser.Result(), null,
+                0L /* last modified date */, 0 /* config version */, allowNonExisting);
+    }
+
     private FontConfig.FontFamily readFamily(String xml)
             throws IOException, XmlPullParserException {
         ByteArrayInputStream buffer = new ByteArrayInputStream(

graphics/java/android/graphics/FontListParser.java

@@ -25,6 +25,7 @@ import android.graphics.fonts.FontVariationAxis;
 import android.os.Build;
 import android.os.LocaleList;
 import android.text.FontConfig;
+import android.util.ArraySet;
 import android.util.Xml;
 
 import org.xmlpull.v1.XmlPullParser;
@@ -37,6 +38,7 @@ import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.regex.Pattern;
 
 /**
@@ -120,7 +122,23 @@ public class FontListParser {
         }
     }
 
-    private static FontConfig readFamilies(
+    /**
+     * Parses the familyset tag in font.xml
+     * @param parser a XML pull parser
+     * @param fontDir A system font directory, e.g. "/system/fonts"
+     * @param customization A OEM font customization
+     * @param updatableFontMap A map of updated font files
+     * @param lastModifiedDate A date that the system font is updated.
+     * @param configVersion A version of system font config.
+     * @param allowNonExistingFile true if allowing non-existing font files during parsing fonts.xml
+     * @return result of fonts.xml
+     *
+     * @throws XmlPullParserException
+     * @throws IOException
+     *
+     * @hide
+     */
+    public static FontConfig readFamilies(
             @NonNull XmlPullParser parser,
             @NonNull String fontDir,
             @NonNull FontCustomizationParser.Result customization,
@@ -159,7 +177,24 @@ public class FontListParser {
         }
 
         families.addAll(oemNamedFamilies.values());
-        return new FontConfig(families, aliases, lastModifiedDate, configVersion);
+
+        // Filters aliases that point to non-existing families.
+        Set<String> namedFamilies = new ArraySet<>();
+        for (int i = 0; i < families.size(); ++i) {
+            String name = families.get(i).getName();
+            if (name != null) {
+                namedFamilies.add(name);
+            }
+        }
+        List<FontConfig.Alias> filtered = new ArrayList<>();
+        for (int i = 0; i < aliases.size(); ++i) {
+            FontConfig.Alias alias = aliases.get(i);
+            if (namedFamilies.contains(alias.getOriginal())) {
+                filtered.add(alias);
+            }
+        }
+
+        return new FontConfig(families, filtered, lastModifiedDate, configVersion);
     }
 
     private static boolean keepReading(XmlPullParser parser)