Add codepoint exclusions API

To be used by unbundled glyph drawing code to filter codepoint sequences
excluded on this platform.

Bug: b/242678495
Test: CodepointExclusionsTest
Change-Id: If928e35a162f5c9bda506a641ce6595855e3e399

core/api/current.txt

@@ -45830,6 +45830,10 @@ package android.text {
     method public android.text.Editable newEditable(CharSequence);
   }
 
+  public final class EmojiConsistency {
+    method @NonNull public static java.util.Set<int[]> getEmojiConsistencySet();
+  }
+
   public interface GetChars extends java.lang.CharSequence {
     method public void getChars(int, int, char[], int);
   }

core/java/android/text/EmojiConsistency.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.text;
+
+import android.annotation.NonNull;
+
+import java.util.Collections;
+import java.util.Set;
+
+
+/**
+ * The set of emoji that should be drawn by the system with the default font for device consistency.
+ *
+ * This is intended to be used only by applications that do custom emoji rendering using tools like
+ * {@link android.text.style.ReplacementSpan} or custom emoji fonts.
+ *
+ * An example of how this should be used:
+ *
+ * <p>
+ *     <ol>
+ *         <li>
+ *             Match emoji for third party custom rendering
+ *         </li>
+ *         <li>
+ *             For each match, check against NonStandardEmoji before displaying custom glyph
+ *         </li>
+ *         <li>
+ *             If in NonStandardEmojiSet, do not display custom glyph (render with
+ *             android.graphics.Typeface.DEFAULT instead)
+ *         </li>
+ *         <li>
+ *             Otherwise, do custom rendering like normal
+ *         </li>
+ *     </ol>
+ * </p>
+ */
+public final class EmojiConsistency {
+    /* Cannot construct */
+    private EmojiConsistency() { }
+
+    /**
+     * The set of emoji that should be drawn by the system with the default font for device
+     * consistency.
+     *
+     * Apps SHOULD attempt to avoid overwriting system emoji rendering with custom emoji glyphs for
+     * these codepoint sequences.
+     *
+     * Apps that display custom emoji glyphs via matching code may filter against this set. On
+     * match, the application SHOULD prefer Typeface.Default instead of a custom glyph
+     *
+     * Apps that use fonts may use this set to add {@link android.text.style.TypefaceSpan} for
+     * android.graphics.Typeface.DEFAULT for matched codepoint sequences.
+     *
+     * Codepoint sequences returned MUST match exactly to be considered a match with the exception
+     * of Variation Selectors.
+     *
+     * All codepoint sequences returned MUST be a complete emoji codepoint sequence as defined by
+     * unicode.
+     *
+     * @return set of codepoint sequences representing codepoints that should be rendered by the
+     * system using the default font.
+     */
+    @NonNull
+    public static Set<int[]> getEmojiConsistencySet() {
+        return Collections.emptySet();
+    }
+
+}

core/tests/coretests/src/android/text/EmojiConsistencyTest.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.text;
+
+import static junit.framework.Assert.assertEquals;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.util.Collections;
+
+@SmallTest
+@RunWith(AndroidJUnit4.class)
+public class EmojiConsistencyTest {
+
+    @Test
+    public void exclusionList_isEmpty() {
+        assertEquals(EmojiConsistency.getEmojiConsistencySet(), Collections.emptySet());
+    }
+}