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 
17 package com.android.inputmethod.event;
18 
19 import java.util.ArrayList;
20 
21 import javax.annotation.Nonnull;
22 
23 /**
24  * A generic interface for combiners. Combiners are objects that transform chains of input events
25  * into committable strings and manage feedback to show to the user on the combining state.
26  */
27 public interface Combiner {
28     /**
29      * Process an event, possibly combining it with the existing state and return the new event.
30      *
31      * If this event does not result in any new event getting passed down the chain, this method
32      * returns null. It may also modify the previous event list if appropriate.
33      *
34      * @param previousEvents the previous events in this composition.
35      * @param event the event to combine with the existing state.
36      * @return the resulting event.
37      */
38     @Nonnull
processEvent(ArrayList<Event> previousEvents, Event event)39     Event processEvent(ArrayList<Event> previousEvents, Event event);
40 
41     /**
42      * Get the feedback that should be shown to the user for the current state of this combiner.
43      * @return A CharSequence representing the feedback to show users. It may include styles.
44      */
getCombiningStateFeedback()45     CharSequence getCombiningStateFeedback();
46 
47     /**
48      * Reset the state of this combiner, for example when the cursor was moved.
49      */
reset()50     void reset();
51 }
52