Improve forward delete key handling.

Forward delete key now deletes characters until the next grapheme
cluster boundary.

Bug: 25737208
Bug: 27035430
Change-Id: Ie2fb510fefa115657cc48063be5319b1eecb30b9
diff --git a/core/java/android/text/method/BaseKeyListener.java b/core/java/android/text/method/BaseKeyListener.java
index e79dfca..3564e11 100644
--- a/core/java/android/text/method/BaseKeyListener.java
+++ b/core/java/android/text/method/BaseKeyListener.java
@@ -16,6 +16,7 @@
 
 package android.text.method;
 
+import android.graphics.Paint;
 import android.icu.lang.UCharacter;
 import android.icu.lang.UProperty;
 import android.view.KeyEvent;
@@ -25,6 +26,8 @@
 import android.text.style.ReplacementSpan;
 import android.widget.TextView;
 
+import com.android.internal.annotations.GuardedBy;
+
 import java.text.BreakIterator;
 import java.util.Arrays;
 import java.util.Collections;
@@ -45,6 +48,11 @@
         implements KeyListener {
     /* package */ static final Object OLD_SEL_START = new NoCopySpan.Concrete();
 
+    private final Object mLock = new Object();
+
+    @GuardedBy("mLock")
+    static Paint sCachedPaint = null;
+
     /**
      * Performs the action that happens when you press the {@link KeyEvent#KEYCODE_DEL} key in
      * a {@link TextView}.  If there is a selection, deletes the selection; otherwise,
@@ -258,20 +266,15 @@
     }
 
     // Returns the end offset to be deleted by a forward delete key from the given offset.
-    private static int getOffsetForForwardDeleteKey(CharSequence text, int offset) {
+    private static int getOffsetForForwardDeleteKey(CharSequence text, int offset, Paint paint) {
         final int len = text.length();
 
         if (offset >= len - 1) {
             return len;
         }
 
-        int codePoint = Character.codePointAt(text, offset);
-        offset += Character.charCount(codePoint);
-        if (offset == len) {
-            return len;
-        }
-
-        // TODO: Handle emoji, combining chars, etc.
+        offset = paint.getTextRunCursor(text, offset, len, Paint.DIRECTION_LTR /* not used */,
+                offset, Paint.CURSOR_AFTER);
 
         return adjustReplacementSpan(text, offset, false /* move to the end */);
     }
@@ -311,7 +314,18 @@
         final int start = Selection.getSelectionEnd(content);
         final int end;
         if (isForwardDelete) {
-            end = getOffsetForForwardDeleteKey(content, start);
+            final Paint paint;
+            if (view instanceof TextView) {
+                paint = ((TextView)view).getPaint();
+            } else {
+                synchronized (mLock) {
+                    if (sCachedPaint == null) {
+                        sCachedPaint = new Paint();
+                    }
+                    paint = sCachedPaint;
+                }
+            }
+            end = getOffsetForForwardDeleteKey(content, start, paint);
         } else {
             end = getOffsetForBackspaceKey(content, start);
         }
diff --git a/core/tests/coretests/src/android/text/method/ForwardDeleteTest.java b/core/tests/coretests/src/android/text/method/ForwardDeleteTest.java
new file mode 100644
index 0000000..da17045
--- /dev/null
+++ b/core/tests/coretests/src/android/text/method/ForwardDeleteTest.java
@@ -0,0 +1,472 @@
+/*
+ * Copyright (C) 2016 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.method;
+
+import android.app.Activity;
+import android.test.suitebuilder.annotation.SmallTest;
+import android.test.suitebuilder.annotation.Suppress;
+import android.text.InputType;
+import android.text.method.BaseKeyListener;
+import android.text.method.KeyListenerTestCase;
+import android.view.KeyEvent;
+import android.widget.EditText;
+import android.widget.TextView.BufferType;
+
+/**
+ * Test forward delete key handling of  {@link android.text.method.BaseKeyListener}.
+ *
+ * TODO: Move some of test cases to the CTS.
+ */
+public class ForwardDeleteTest extends KeyListenerTestCase {
+    private static final BaseKeyListener mKeyListener = new BaseKeyListener() {
+        public int getInputType() {
+            return InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_NORMAL;
+        }
+    };
+
+    // Sync the state to the TextView and call onKeyDown with KEYCODE_FORWARD_DEL key event.
+    // Then update the state to the result of TextView.
+    private void forwardDelete(final EditorState state, int modifiers) {
+        mActivity.runOnUiThread(new Runnable() {
+            public void run() {
+                mTextView.setText(state.mText, BufferType.EDITABLE);
+                mTextView.setKeyListener(mKeyListener);
+                mTextView.setSelection(state.mSelectionStart, state.mSelectionEnd);
+            }
+        });
+        mInstrumentation.waitForIdleSync();
+        assertTrue(mTextView.hasWindowFocus());
+
+        final KeyEvent keyEvent = getKey(KeyEvent.KEYCODE_FORWARD_DEL, modifiers);
+        mActivity.runOnUiThread(new Runnable() {
+            public void run() {
+                mTextView.onKeyDown(keyEvent.getKeyCode(), keyEvent);
+            }
+        });
+        mInstrumentation.waitForIdleSync();
+
+        state.mText = mTextView.getText();
+        state.mSelectionStart = mTextView.getSelectionStart();
+        state.mSelectionEnd = mTextView.getSelectionEnd();
+    }
+
+    @SmallTest
+    public void testSurrogatePairs() {
+        EditorState state = new EditorState();
+
+        // U+1F441 is EYE
+        state.setByString("| U+1F441");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // U+1F5E8 is LEFT SPEECH BUBBLE
+        state.setByString("| U+1F441 U+1F5E8");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F5E8");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // TODO: introduce edge cases.
+    }
+
+    @SmallTest
+    public void testReplacementSpan() {
+        EditorState state = new EditorState();
+
+        state.setByString("| 'abc' ( 'de' ) 'fg'");
+        forwardDelete(state, 0);
+        state.assertEquals("| 'bc' ( 'de' ) 'fg'");
+        forwardDelete(state, 0);
+        state.assertEquals("| 'c' ( 'de' ) 'fg'");
+        forwardDelete(state, 0);
+        state.assertEquals("| ( 'de' ) 'fg'");
+        forwardDelete(state, 0);
+        state.assertEquals("| 'fg'");
+        forwardDelete(state, 0);
+        state.assertEquals("| 'g'");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("'abc' [ ( 'de' ) ] 'fg'");
+        forwardDelete(state, 0);
+        state.assertEquals("'abc' | 'fg'");
+        forwardDelete(state, 0);
+        state.assertEquals("'abc' | 'g'");
+        forwardDelete(state, 0);
+        state.assertEquals("'abc' |");
+        forwardDelete(state, 0);
+        state.assertEquals("'abc' |");
+
+        state.setByString("'ab' [ 'c' ( 'de' ) 'f' ] 'g'");
+        forwardDelete(state, 0);
+        state.assertEquals("'ab' | 'g'");
+        forwardDelete(state, 0);
+        state.assertEquals("'ab' |");
+        forwardDelete(state, 0);
+        state.assertEquals("'ab' |");
+
+        // TODO: introduce edge cases.
+    }
+
+    @SmallTest
+    public void testCombiningEnclosingKeycaps() {
+        EditorState state = new EditorState();
+
+        // U+20E3 is COMBINING ENCLOSING KEYCAP.
+        state.setByString("| '1' U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Edge cases
+        // multiple COMBINING ENCLOSING KEYCAP
+        state.setByString("| '1' U+20E3 U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Isolated COMBINING ENCLOSING KEYCAP
+        state.setByString("| U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Isolated multiple COMBINING ENCLOSING KEYCAP
+        state.setByString("| U+20E3 U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+    }
+
+    @SmallTest
+    public void testVariationSelector() {
+        EditorState state = new EditorState();
+
+        // U+FE0F is VARIATION SELECTOR-16.
+        state.setByString("| '#' U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // U+E0100 is VARIATION SELECTOR-17.
+        state.setByString("| U+845B U+E0100");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Edge cases
+        // Isolated variation selectors
+        state.setByString("| U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| U+E0100");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Isolated multiple variation selectors
+        state.setByString("| U+FE0F U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| U+FE0F U+E0100");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| U+E0100 U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| U+E0100 U+E0100");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Multiple variation selectors
+        state.setByString("| '#' U+FE0F U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| '#' U+FE0F U+E0100");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| U+845B U+E0100 U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| U+845B U+E0100 U+E0100");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+    }
+
+    @SmallTest
+    public void testEmojiZeroWidthJoinerSequence() {
+        EditorState state = new EditorState();
+
+        // U+200D is ZERO WIDTH JOINER.
+        state.setByString("| U+1F441 U+200D U+1F5E8");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| U+1F468 U+200D U+2764 U+FE0F U+200D U+1F48B U+200D U+1F468");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Edge cases
+        // End with ZERO WIDTH JOINER
+        state.setByString("| U+1F441 U+200D");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Start with ZERO WIDTH JOINER
+        state.setByString("| U+200D U+1F5E8");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F5E8");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Multiple ZERO WIDTH JOINER
+        state.setByString("| U+1F441 U+200D U+200D U+1F5E8");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F5E8");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Isolated ZERO WIDTH JOINER
+        state.setByString("| U+200D");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Isolated multiple ZERO WIDTH JOINER
+        state.setByString("| U+200D U+200D");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+    }
+
+    @SmallTest
+    public void testFlags() {
+        EditorState state = new EditorState();
+
+        // U+1F1FA is REGIONAL INDICATOR SYMBOL LETTER U.
+        // U+1F1F8 is REGIONAL INDICATOR SYMBOL LETTER S.
+        state.setByString("| U+1F1FA U+1F1F8");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        state.setByString("| U+1F1FA U+1F1F8 U+1F1FA U+1F1F8");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F1FA U+1F1F8");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Edge cases
+        // Isolated regional indicator symbol
+        state.setByString("| U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Odd numbered regional indicator symbols
+        state.setByString("| U+1F1FA U+1F1F8 U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+    }
+
+    @SmallTest
+    public void testEmojiModifier() {
+        EditorState state = new EditorState();
+
+        // U+1F3FB is EMOJI MODIFIER FITZPATRICK TYPE-1-2.
+        state.setByString("| U+1F466 U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Edge cases
+        // Isolated emoji modifier
+        state.setByString("| U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Isolated multiple emoji modifier
+        state.setByString("| U+1F3FB U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Multiple emoji modifiers
+        state.setByString("| U+1F466 U+1F3FB U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+    }
+
+    @SmallTest
+    public void testMixedEdgeCases() {
+        EditorState state = new EditorState();
+
+        // COMBINING ENCLOSING KEYCAP + variation selector
+        state.setByString("| '1' U+20E3 U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Variation selector + COMBINING ENCLOSING KEYCAP
+        state.setByString("| U+2665 U+FE0F U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // COMBINING ENCLOSING KEYCAP + ending with ZERO WIDTH JOINER
+        state.setByString("| '1' U+20E3 U+200D");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // COMBINING ENCLOSING KEYCAP + ZERO WIDTH JOINER
+        state.setByString("| '1' U+20E3 U+200D U+1F5E8");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F5E8 ");
+
+        // Start with ZERO WIDTH JOINER + COMBINING ENCLOSING KEYCAP
+        state.setByString("| U+200D U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // ZERO WIDTH JOINER + COMBINING ENCLOSING KEYCAP
+        state.setByString("| U+1F441 U+200D U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // COMBINING ENCLOSING KEYCAP + regional indicator symbol
+        state.setByString("| '1' U+20E3 U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Regional indicator symbol + COMBINING ENCLOSING KEYCAP
+        state.setByString("| U+1F1FA U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // COMBINING ENCLOSING KEYCAP + emoji modifier
+        state.setByString("| '1' U+20E3 U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F3FB");
+
+        // Emoji modifier + COMBINING ENCLOSING KEYCAP
+        state.setByString("| U+1F466 U+1F3FB U+20E3");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Variation selector + end with ZERO WIDTH JOINER
+        state.setByString("| U+2665 U+FE0F U+200D");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Variation selector + ZERO WIDTH JOINER
+        state.setByString("| U+1F469 U+200D U+2764 U+FE0F U+200D U+1F469");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Start with ZERO WIDTH JOINER + variation selector
+        state.setByString("| U+200D U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // ZERO WIDTH JOINER + variation selector
+        state.setByString("| U+1F469 U+200D U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Variation selector + regional indicator symbol
+        state.setByString("| U+2665 U+FE0F U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Regional indicator symbol + variation selector
+        state.setByString("| U+1F1FA U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Variation selector + emoji modifier
+        state.setByString("| U+2665 U+FE0F U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F3FB");
+
+        // Emoji modifier + variation selector
+        state.setByString("| U+1F466 U+1F3FB U+FE0F");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Start with ZERO WIDTH JOINER + regional indicator symbol
+        state.setByString("| U+200D U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // ZERO WIDTH JOINER + regional indicator symbol
+        state.setByString("| U+1F469 U+200D U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F1FA");
+
+        // Regional indicator symbol + end with ZERO WIDTH JOINER
+        state.setByString("| U+1F1FA U+200D");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Regional indicator symbol + ZERO WIDTH JOINER
+        state.setByString("| U+1F1FA U+200D U+1F469");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F469");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Start with ZERO WIDTH JOINER + emoji modifier
+        state.setByString("| U+200D U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F3FB");
+
+        // ZERO WIDTH JOINER + emoji modifier
+        state.setByString("| U+1F469 U+200D U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F3FB");
+
+        // Emoji modifier + end with ZERO WIDTH JOINER
+        state.setByString("| U+1F466 U+1F3FB U+200D");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Emoji modifier + ZERO WIDTH JOINER
+        state.setByString("| U+1F466 U+1F3FB U+200D U+1F469");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F469");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Regional indicator symbol + emoji modifier
+        state.setByString("| U+1F1FA U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F3FB");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+
+        // Emoji modifier + regional indicator symbol
+        state.setByString("| U+1F466 U+1F3FB U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("| U+1F1FA");
+        forwardDelete(state, 0);
+        state.assertEquals("|");
+    }
+}