DeadKeyCombiner.java revision e0bad8e988a23553181fb670f8a2589a79f22c40 
1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.inputmethod.event;
18
19import android.text.TextUtils;
20import android.view.KeyCharacterMap;
21
22import com.android.inputmethod.latin.Constants;
23
24import java.util.ArrayList;
25
26import javax.annotation.Nonnull;
27
28/**
29 * A combiner that handles dead keys.
30 */
31public class DeadKeyCombiner implements Combiner {
32    // TODO: make this a list of events instead
33    final StringBuilder mDeadSequence = new StringBuilder();
34
35    @Override
36    @Nonnull
37    public Event processEvent(final ArrayList<Event> previousEvents, final Event event) {
38        if (TextUtils.isEmpty(mDeadSequence)) {
39            // No dead char is currently being tracked: this is the most common case.
40            if (event.isDead()) {
41                // The event was a dead key. Start tracking it.
42                mDeadSequence.appendCodePoint(event.mCodePoint);
43                return Event.createConsumedEvent(event);
44            }
45            // Regular keystroke when not keeping track of a dead key. Simply said, there are
46            // no dead keys at all in the current input, so this combiner has nothing to do and
47            // simply returns the event as is. The majority of events will go through this path.
48            return event;
49        } else {
50            // TODO: Allow combining for several dead chars rather than only the first one.
51            // The framework doesn't know how to do this now.
52            final int deadCodePoint = mDeadSequence.codePointAt(0);
53            mDeadSequence.setLength(0);
54            final int resultingCodePoint =
55                    KeyCharacterMap.getDeadChar(deadCodePoint, event.mCodePoint);
56            if (0 == resultingCodePoint) {
57                // We can't combine both characters. We need to commit the dead key as a separate
58                // character, and the next char too unless it's a space (because as a special case,
59                // dead key + space should result in only the dead key being committed - that's
60                // how dead keys work).
61                // If the event is a space, we should commit the dead char alone, but if it's
62                // not, we need to commit both.
63                // TODO: this is not necessarily triggered by hardware key events, so it's not
64                // a good idea to masquerade as one. This should be typed as a software
65                // composite event or something.
66                return Event.createHardwareKeypressEvent(deadCodePoint, event.mKeyCode,
67                        Constants.CODE_SPACE == event.mCodePoint ? null : event /* next */,
68                        false /* isKeyRepeat */);
69            } else {
70                // We could combine the characters.
71                return Event.createHardwareKeypressEvent(resultingCodePoint, event.mKeyCode,
72                        null /* next */, false /* isKeyRepeat */);
73            }
74        }
75    }
76
77    @Override
78    public void reset() {
79        mDeadSequence.setLength(0);
80    }
81
82    @Override
83    public CharSequence getCombiningStateFeedback() {
84        return mDeadSequence;
85    }
86}
87