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      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.keyboard.internal;
     18 
     19 import android.content.res.Resources;
     20 import android.util.DisplayMetrics;
     21 import android.util.Log;
     22 
     23 import com.android.inputmethod.latin.R;
     24 import com.android.inputmethod.latin.common.Constants;
     25 import com.android.inputmethod.latin.define.DebugFlags;
     26 
     27 // This hack is applied to certain classes of tablets.
     28 public final class BogusMoveEventDetector {
     29     private static final String TAG = BogusMoveEventDetector.class.getSimpleName();
     30     private static final boolean DEBUG_MODE = DebugFlags.DEBUG_ENABLED;
     31 
     32     // Move these thresholds to resource.
     33     // These thresholds' unit is a diagonal length of a key.
     34     private static final float BOGUS_MOVE_ACCUMULATED_DISTANCE_THRESHOLD = 0.53f;
     35     private static final float BOGUS_MOVE_RADIUS_THRESHOLD = 1.14f;
     36 
     37     private static boolean sNeedsProximateBogusDownMoveUpEventHack;
     38 
     39     public static void init(final Resources res) {
     40         // The proximate bogus down move up event hack is needed for a device such like,
     41         // 1) is large tablet, or 2) is small tablet and the screen density is less than hdpi.
     42         // Though it seems odd to use screen density as criteria of the quality of the touch
     43         // screen, the small table that has a less density screen than hdpi most likely has been
     44         // made with the touch screen that needs the hack.
     45         final int screenMetrics = res.getInteger(R.integer.config_screen_metrics);
     46         final boolean isLargeTablet = (screenMetrics == Constants.SCREEN_METRICS_LARGE_TABLET);
     47         final boolean isSmallTablet = (screenMetrics == Constants.SCREEN_METRICS_SMALL_TABLET);
     48         final int densityDpi = res.getDisplayMetrics().densityDpi;
     49         final boolean hasLowDensityScreen = (densityDpi < DisplayMetrics.DENSITY_HIGH);
     50         final boolean needsTheHack = isLargeTablet || (isSmallTablet && hasLowDensityScreen);
     51         if (DEBUG_MODE) {
     52             final int sw = res.getConfiguration().smallestScreenWidthDp;
     53             Log.d(TAG, "needsProximateBogusDownMoveUpEventHack=" + needsTheHack
     54                     + " smallestScreenWidthDp=" + sw + " densityDpi=" + densityDpi
     55                     + " screenMetrics=" + screenMetrics);
     56         }
     57         sNeedsProximateBogusDownMoveUpEventHack = needsTheHack;
     58     }
     59 
     60     private int mAccumulatedDistanceThreshold;
     61     private int mRadiusThreshold;
     62 
     63     // Accumulated distance from actual and artificial down keys.
     64     /* package */ int mAccumulatedDistanceFromDownKey;
     65     private int mActualDownX;
     66     private int mActualDownY;
     67 
     68     public void setKeyboardGeometry(final int keyWidth, final int keyHeight) {
     69         final float keyDiagonal = (float)Math.hypot(keyWidth, keyHeight);
     70         mAccumulatedDistanceThreshold = (int)(
     71                 keyDiagonal * BOGUS_MOVE_ACCUMULATED_DISTANCE_THRESHOLD);
     72         mRadiusThreshold = (int)(keyDiagonal * BOGUS_MOVE_RADIUS_THRESHOLD);
     73     }
     74 
     75     public void onActualDownEvent(final int x, final int y) {
     76         mActualDownX = x;
     77         mActualDownY = y;
     78     }
     79 
     80     public void onDownKey() {
     81         mAccumulatedDistanceFromDownKey = 0;
     82     }
     83 
     84     public void onMoveKey(final int distance) {
     85         mAccumulatedDistanceFromDownKey += distance;
     86     }
     87 
     88     public boolean hasTraveledLongDistance(final int x, final int y) {
     89         if (!sNeedsProximateBogusDownMoveUpEventHack) {
     90             return false;
     91         }
     92         final int dx = Math.abs(x - mActualDownX);
     93         final int dy = Math.abs(y - mActualDownY);
     94         // A bogus move event should be a horizontal movement. A vertical movement might be
     95         // a sloppy typing and should be ignored.
     96         return dx >= dy && mAccumulatedDistanceFromDownKey >= mAccumulatedDistanceThreshold;
     97     }
     98 
     99     public int getAccumulatedDistanceFromDownKey() {
    100         return mAccumulatedDistanceFromDownKey;
    101     }
    102 
    103     public int getDistanceFromDownEvent(final int x, final int y) {
    104         return getDistance(x, y, mActualDownX, mActualDownY);
    105     }
    106 
    107     private static int getDistance(final int x1, final int y1, final int x2, final int y2) {
    108         return (int)Math.hypot(x1 - x2, y1 - y2);
    109     }
    110 
    111     public boolean isCloseToActualDownEvent(final int x, final int y) {
    112         return sNeedsProximateBogusDownMoveUpEventHack
    113                 && getDistanceFromDownEvent(x, y) < mRadiusThreshold;
    114     }
    115 }
    116