/*
* Copyright (C) 2010 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.keyboard;
import android.util.Log;
import java.util.Arrays;
import java.util.List;
public class KeyDetector {
private static final String TAG = KeyDetector.class.getSimpleName();
private static final boolean DEBUG = false;
public static final int NOT_A_CODE = -1;
public static final int NOT_A_KEY = -1;
private final int mKeyHysteresisDistanceSquared;
private Keyboard mKeyboard;
private int mCorrectionX;
private int mCorrectionY;
private boolean mProximityCorrectOn;
private int mProximityThresholdSquare;
// working area
private static final int MAX_NEARBY_KEYS = 12;
private final int[] mDistances = new int[MAX_NEARBY_KEYS];
private final int[] mIndices = new int[MAX_NEARBY_KEYS];
/**
* This class handles key detection.
*
* @param keyHysteresisDistance if the pointer movement distance is smaller than this, the
* movement will not been handled as meaningful movement. The unit is pixel.
*/
public KeyDetector(float keyHysteresisDistance) {
mKeyHysteresisDistanceSquared = (int)(keyHysteresisDistance * keyHysteresisDistance);
}
public void setKeyboard(Keyboard keyboard, float correctionX, float correctionY) {
if (keyboard == null)
throw new NullPointerException();
mCorrectionX = (int)correctionX;
mCorrectionY = (int)correctionY;
mKeyboard = keyboard;
final int threshold = keyboard.mMostCommonKeyWidth;
mProximityThresholdSquare = threshold * threshold;
}
public int getKeyHysteresisDistanceSquared() {
return mKeyHysteresisDistanceSquared;
}
protected int getTouchX(int x) {
return x + mCorrectionX;
}
protected int getTouchY(int y) {
return y + mCorrectionY;
}
public Keyboard getKeyboard() {
if (mKeyboard == null)
throw new IllegalStateException("keyboard isn't set");
return mKeyboard;
}
public void setProximityCorrectionEnabled(boolean enabled) {
mProximityCorrectOn = enabled;
}
public boolean isProximityCorrectionEnabled() {
return mProximityCorrectOn;
}
public void setProximityThreshold(int threshold) {
mProximityThresholdSquare = threshold * threshold;
}
public boolean alwaysAllowsSlidingInput() {
return false;
}
/**
* Computes maximum size of the array that can contain all nearby key indices returned by
* {@link #getKeyIndexAndNearbyCodes}.
*
* @return Returns maximum size of the array that can contain all nearby key indices returned
* by {@link #getKeyIndexAndNearbyCodes}.
*/
protected int getMaxNearbyKeys() {
return MAX_NEARBY_KEYS;
}
/**
* Allocates array that can hold all key indices returned by {@link #getKeyIndexAndNearbyCodes}
* method. The maximum size of the array should be computed by {@link #getMaxNearbyKeys}.
*
* @return Allocates and returns an array that can hold all key indices returned by
* {@link #getKeyIndexAndNearbyCodes} method. All elements in the returned array are
* initialized by {@link #NOT_A_CODE} value.
*/
public int[] newCodeArray() {
int[] codes = new int[getMaxNearbyKeys()];
Arrays.fill(codes, NOT_A_CODE);
return codes;
}
private void initializeNearbyKeys() {
Arrays.fill(mDistances, Integer.MAX_VALUE);
Arrays.fill(mIndices, NOT_A_KEY);
}
/**
* Insert the key into nearby keys buffer and sort nearby keys by ascending order of distance.
* If the distance of two keys are the same, the key which the point is on should be considered
* as a closer one.
*
* @param keyIndex index of the key.
* @param distance distance between the key's edge and user touched point.
* @param isOnKey true if the point is on the key.
* @return order of the key in the nearby buffer, 0 if it is the nearest key.
*/
private int sortNearbyKeys(int keyIndex, int distance, boolean isOnKey) {
final int[] distances = mDistances;
final int[] indices = mIndices;
for (int insertPos = 0; insertPos < distances.length; insertPos++) {
final int comparingDistance = distances[insertPos];
if (distance < comparingDistance || (distance == comparingDistance && isOnKey)) {
final int nextPos = insertPos + 1;
if (nextPos < distances.length) {
System.arraycopy(distances, insertPos, distances, nextPos,
distances.length - nextPos);
System.arraycopy(indices, insertPos, indices, nextPos,
indices.length - nextPos);
}
distances[insertPos] = distance;
indices[insertPos] = keyIndex;
return insertPos;
}
}
return distances.length;
}
private void getNearbyKeyCodes(final int[] allCodes) {
final List<Key> keys = getKeyboard().mKeys;
final int[] indices = mIndices;
// allCodes[0] should always have the key code even if it is a non-letter key.
if (indices[0] == NOT_A_KEY) {
allCodes[0] = NOT_A_CODE;
return;
}
int numCodes = 0;
for (int j = 0; j < indices.length && numCodes < allCodes.length; j++) {
final int index = indices[j];
if (index == NOT_A_KEY)
break;
final int code = keys.get(index).mCode;
// filter out a non-letter key from nearby keys
if (code < Keyboard.CODE_SPACE)
continue;
allCodes[numCodes++] = code;
}
}
/**
* Finds all possible nearby key indices around a touch event point and returns the nearest key
* index. The algorithm to determine the nearby keys depends on the threshold set by
* {@link #setProximityThreshold(int)} and the mode set by
* {@link #setProximityCorrectionEnabled(boolean)}.
*
* @param x The x-coordinate of a touch point
* @param y The y-coordinate of a touch point
* @param allCodes All nearby key code except functional key are returned in this array
* @return The nearest key index
*/
public int getKeyIndexAndNearbyCodes(int x, int y, final int[] allCodes) {
final List<Key> keys = getKeyboard().mKeys;
final int touchX = getTouchX(x);
final int touchY = getTouchY(y);
initializeNearbyKeys();
int primaryIndex = NOT_A_KEY;
for (final int index : mKeyboard.getNearestKeys(touchX, touchY)) {
final Key key = keys.get(index);
final boolean isOnKey = key.isOnKey(touchX, touchY);
final int distance = key.squaredDistanceToEdge(touchX, touchY);
if (isOnKey || (mProximityCorrectOn && distance < mProximityThresholdSquare)) {
final int insertedPosition = sortNearbyKeys(index, distance, isOnKey);
if (insertedPosition == 0 && isOnKey)
primaryIndex = index;
}
}
if (allCodes != null && allCodes.length > 0) {
getNearbyKeyCodes(allCodes);
if (DEBUG) {
Log.d(TAG, "x=" + x + " y=" + y
+ " primary="
+ (primaryIndex == NOT_A_KEY ? "none" : keys.get(primaryIndex).mCode)
+ " codes=" + Arrays.toString(allCodes));
}
}
return primaryIndex;
}
}