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/*
* Copyright (C) 2014 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 com.android.inputmethod.event;
import android.text.SpannableStringBuilder;
import android.text.TextUtils;
import com.android.inputmethod.latin.Constants;
import com.android.inputmethod.latin.utils.CollectionUtils;
import java.util.ArrayList;
/**
* This class implements the logic chain between receiving events and generating code points.
*
* Event sources are multiple. It may be a hardware keyboard, a D-PAD, a software keyboard,
* or any exotic input source.
* This class will orchestrate the composing chain that starts with an event as its input. Each
* composer will be given turns one after the other.
* The output is composed of two sequences of code points: the first, representing the already
* finished combining part, will be shown normally as the composing string, while the second is
* feedback on the composing state and will typically be shown with different styling such as
* a colored background.
*/
public class CombinerChain {
// The already combined text, as described above
private StringBuilder mCombinedText;
// The feedback on the composing state, as described above
private SpannableStringBuilder mStateFeedback;
private final ArrayList<Combiner> mCombiners;
/**
* Create an combiner chain.
*
* The combiner chain takes events as inputs and outputs code points and combining state.
* For example, if the input language is Japanese, the combining chain will typically perform
* kana conversion.
*
* @param combinerList A list of combiners to be applied in order.
*/
public CombinerChain(final Combiner... combinerList) {
mCombiners = CollectionUtils.newArrayList();
// The dead key combiner is always active, and always first
mCombiners.add(new DeadKeyCombiner());
mCombinedText = new StringBuilder();
mStateFeedback = new SpannableStringBuilder();
}
public void reset() {
mCombinedText.setLength(0);
mStateFeedback.clear();
for (final Combiner c : mCombiners) {
c.reset();
}
}
/**
* Pass a new event through the whole chain.
* @param previousEvents the list of previous events in this composition
* @param newEvent the new event to process
*/
public void processEvent(final ArrayList<Event> previousEvents, final Event newEvent) {
final ArrayList<Event> modifiablePreviousEvents = new ArrayList<Event>(previousEvents);
Event event = newEvent;
for (final Combiner combiner : mCombiners) {
// A combiner can never return more than one event; it can return several
// code points, but they should be encapsulated within one event.
event = combiner.processEvent(modifiablePreviousEvents, event);
if (null == event) {
// Combiners return null if they eat the event.
break;
}
}
if (null != event) {
// TODO: figure out the generic way of doing this
if (Constants.CODE_DELETE == event.mKeyCode) {
final int length = mCombinedText.length();
if (length > 0) {
final int lastCodePoint = mCombinedText.codePointBefore(length);
mCombinedText.delete(length - Character.charCount(lastCodePoint), length);
}
} else {
final CharSequence textToCommit = event.getTextToCommit();
if (!TextUtils.isEmpty(textToCommit)) {
mCombinedText.append(textToCommit);
}
}
}
mStateFeedback.clear();
for (int i = mCombiners.size() - 1; i >= 0; --i) {
mStateFeedback.append(mCombiners.get(i).getCombiningStateFeedback());
}
}
/**
* Get the char sequence that should be displayed as the composing word. It may include
* styling spans.
*/
public CharSequence getComposingWordWithCombiningFeedback() {
final SpannableStringBuilder s = new SpannableStringBuilder(mCombinedText);
return s.append(mStateFeedback);
}
}
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