1/*
2 * Copyright (C) 2010 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.keyboard;
18
19/**
20 * This class handles key detection.
21 */
22public class KeyDetector {
23    private final int mKeyHysteresisDistanceSquared;
24    private final int mKeyHysteresisDistanceForSlidingModifierSquared;
25
26    private Keyboard mKeyboard;
27    private int mCorrectionX;
28    private int mCorrectionY;
29
30    public KeyDetector() {
31        this(0.0f /* keyHysteresisDistance */, 0.0f /* keyHysteresisDistanceForSlidingModifier */);
32    }
33
34    /**
35     * Key detection object constructor with key hysteresis distances.
36     *
37     * @param keyHysteresisDistance if the pointer movement distance is smaller than this, the
38     * movement will not be handled as meaningful movement. The unit is pixel.
39     * @param keyHysteresisDistanceForSlidingModifier the same parameter for sliding input that
40     * starts from a modifier key such as shift and symbols key.
41     */
42    public KeyDetector(final float keyHysteresisDistance,
43            final float keyHysteresisDistanceForSlidingModifier) {
44        mKeyHysteresisDistanceSquared = (int)(keyHysteresisDistance * keyHysteresisDistance);
45        mKeyHysteresisDistanceForSlidingModifierSquared = (int)(
46                keyHysteresisDistanceForSlidingModifier * keyHysteresisDistanceForSlidingModifier);
47    }
48
49    public void setKeyboard(final Keyboard keyboard, final float correctionX,
50            final float correctionY) {
51        if (keyboard == null) {
52            throw new NullPointerException();
53        }
54        mCorrectionX = (int)correctionX;
55        mCorrectionY = (int)correctionY;
56        mKeyboard = keyboard;
57    }
58
59    public int getKeyHysteresisDistanceSquared(final boolean isSlidingFromModifier) {
60        return isSlidingFromModifier
61                ? mKeyHysteresisDistanceForSlidingModifierSquared : mKeyHysteresisDistanceSquared;
62    }
63
64    public int getTouchX(final int x) {
65        return x + mCorrectionX;
66    }
67
68    // TODO: Remove vertical correction.
69    public int getTouchY(final int y) {
70        return y + mCorrectionY;
71    }
72
73    public Keyboard getKeyboard() {
74        return mKeyboard;
75    }
76
77    public boolean alwaysAllowsKeySelectionByDraggingFinger() {
78        return false;
79    }
80
81    /**
82     * Detect the key whose hitbox the touch point is in.
83     *
84     * @param x The x-coordinate of a touch point
85     * @param y The y-coordinate of a touch point
86     * @return the key that the touch point hits.
87     */
88    public Key detectHitKey(final int x, final int y) {
89        if (mKeyboard == null) {
90            return null;
91        }
92        final int touchX = getTouchX(x);
93        final int touchY = getTouchY(y);
94
95        int minDistance = Integer.MAX_VALUE;
96        Key primaryKey = null;
97        for (final Key key: mKeyboard.getNearestKeys(touchX, touchY)) {
98            // An edge key always has its enlarged hitbox to respond to an event that occurred in
99            // the empty area around the key. (@see Key#markAsLeftEdge(KeyboardParams)} etc.)
100            if (!key.isOnKey(touchX, touchY)) {
101                continue;
102            }
103            final int distance = key.squaredDistanceToEdge(touchX, touchY);
104            if (distance > minDistance) {
105                continue;
106            }
107            // To take care of hitbox overlaps, we compare key's code here too.
108            if (primaryKey == null || distance < minDistance
109                    || key.getCode() > primaryKey.getCode()) {
110                minDistance = distance;
111                primaryKey = key;
112            }
113        }
114        return primaryKey;
115    }
116}
117