LatinIME/java/src/com/android/inputmethod/keyboard/KeyDetector.java

/*
 * 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;

/**
 * This class handles key detection.
 */
public class KeyDetector {
    private final int mKeyHysteresisDistanceSquared;
    private final int mKeyHysteresisDistanceForSlidingModifierSquared;

    private Keyboard mKeyboard;
    private int mCorrectionX;
    private int mCorrectionY;

    public KeyDetector() {
        this(0.0f /* keyHysteresisDistance */, 0.0f /* keyHysteresisDistanceForSlidingModifier */);
    }

    /**
     * Key detection object constructor with key hysteresis distances.
     *
     * @param keyHysteresisDistance if the pointer movement distance is smaller than this, the
     * movement will not be handled as meaningful movement. The unit is pixel.
     * @param keyHysteresisDistanceForSlidingModifier the same parameter for sliding input that
     * starts from a modifier key such as shift and symbols key.
     */
    public KeyDetector(final float keyHysteresisDistance,
            final float keyHysteresisDistanceForSlidingModifier) {
        mKeyHysteresisDistanceSquared = (int)(keyHysteresisDistance * keyHysteresisDistance);
        mKeyHysteresisDistanceForSlidingModifierSquared = (int)(
                keyHysteresisDistanceForSlidingModifier * keyHysteresisDistanceForSlidingModifier);
    }

    public void setKeyboard(final Keyboard keyboard, final float correctionX,
            final float correctionY) {
        if (keyboard == null) {
            throw new NullPointerException();
        }
        mCorrectionX = (int)correctionX;
        mCorrectionY = (int)correctionY;
        mKeyboard = keyboard;
    }

    public int getKeyHysteresisDistanceSquared(final boolean isSlidingFromModifier) {
        return isSlidingFromModifier
                ? mKeyHysteresisDistanceForSlidingModifierSquared : mKeyHysteresisDistanceSquared;
    }

    public int getTouchX(final int x) {
        return x + mCorrectionX;
    }

    // TODO: Remove vertical correction.
    public int getTouchY(final int y) {
        return y + mCorrectionY;
    }

    public Keyboard getKeyboard() {
        return mKeyboard;
    }

    public boolean alwaysAllowsKeySelectionByDraggingFinger() {
        return false;
    }

    /**
     * Detect the key whose hitbox the touch point is in.
     *
     * @param x The x-coordinate of a touch point
     * @param y The y-coordinate of a touch point
     * @return the key that the touch point hits.
     */
    public Key detectHitKey(final int x, final int y) {
        if (mKeyboard == null) {
            return null;
        }
        final int touchX = getTouchX(x);
        final int touchY = getTouchY(y);

        int minDistance = Integer.MAX_VALUE;
        Key primaryKey = null;
        for (final Key key: mKeyboard.getNearestKeys(touchX, touchY)) {
            // An edge key always has its enlarged hitbox to respond to an event that occurred in
            // the empty area around the key. (@see Key#markAsLeftEdge(KeyboardParams)} etc.)
            if (!key.isOnKey(touchX, touchY)) {
                continue;
            }
            final int distance = key.squaredDistanceToEdge(touchX, touchY);
            if (distance > minDistance) {
                continue;
            }
            // To take care of hitbox overlaps, we compare key's code here too.
            if (primaryKey == null || distance < minDistance
                    || key.getCode() > primaryKey.getCode()) {
                minDistance = distance;
                primaryKey = key;
            }
        }
        return primaryKey;
    }
}