1/*
2 * Copyright (C) 2012 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 */
16package com.android.gallery3d.util;
17
18import android.annotation.TargetApi;
19import android.graphics.Matrix;
20import android.util.FloatMath;
21import android.view.MotionEvent;
22import android.view.MotionEvent.PointerCoords;
23
24import com.android.gallery3d.common.ApiHelper;
25
26public final class MotionEventHelper {
27    private MotionEventHelper() {}
28
29    public static MotionEvent transformEvent(MotionEvent e, Matrix m) {
30        // We try to use the new transform method if possible because it uses
31        // less memory.
32        if (ApiHelper.HAS_MOTION_EVENT_TRANSFORM) {
33            return transformEventNew(e, m);
34        } else {
35            return transformEventOld(e, m);
36        }
37    }
38
39    @TargetApi(ApiHelper.VERSION_CODES.HONEYCOMB)
40    private static MotionEvent transformEventNew(MotionEvent e, Matrix m) {
41        MotionEvent newEvent = MotionEvent.obtain(e);
42        newEvent.transform(m);
43        return newEvent;
44    }
45
46    // This is copied from Input.cpp in the android framework.
47    private static MotionEvent transformEventOld(MotionEvent e, Matrix m) {
48        long downTime = e.getDownTime();
49        long eventTime = e.getEventTime();
50        int action = e.getAction();
51        int pointerCount = e.getPointerCount();
52        int[] pointerIds = getPointerIds(e);
53        PointerCoords[] pointerCoords = getPointerCoords(e);
54        int metaState = e.getMetaState();
55        float xPrecision = e.getXPrecision();
56        float yPrecision = e.getYPrecision();
57        int deviceId = e.getDeviceId();
58        int edgeFlags = e.getEdgeFlags();
59        int source = e.getSource();
60        int flags = e.getFlags();
61
62        // Copy the x and y coordinates into an array, map them, and copy back.
63        float[] xy = new float[pointerCoords.length * 2];
64        for (int i = 0; i < pointerCount;i++) {
65            xy[2 * i] = pointerCoords[i].x;
66            xy[2 * i + 1] = pointerCoords[i].y;
67        }
68        m.mapPoints(xy);
69        for (int i = 0; i < pointerCount;i++) {
70            pointerCoords[i].x = xy[2 * i];
71            pointerCoords[i].y = xy[2 * i + 1];
72            pointerCoords[i].orientation = transformAngle(
73                m, pointerCoords[i].orientation);
74        }
75
76        MotionEvent n = MotionEvent.obtain(downTime, eventTime, action,
77                pointerCount, pointerIds, pointerCoords, metaState, xPrecision,
78                yPrecision, deviceId, edgeFlags, source, flags);
79
80        return n;
81    }
82
83    private static int[] getPointerIds(MotionEvent e) {
84        int n = e.getPointerCount();
85        int[] r = new int[n];
86        for (int i = 0; i < n; i++) {
87            r[i] = e.getPointerId(i);
88        }
89        return r;
90    }
91
92    private static PointerCoords[] getPointerCoords(MotionEvent e) {
93        int n = e.getPointerCount();
94        PointerCoords[] r = new PointerCoords[n];
95        for (int i = 0; i < n; i++) {
96            r[i] = new PointerCoords();
97            e.getPointerCoords(i, r[i]);
98        }
99        return r;
100    }
101
102    private static float transformAngle(Matrix m, float angleRadians) {
103        // Construct and transform a vector oriented at the specified clockwise
104        // angle from vertical.  Coordinate system: down is increasing Y, right is
105        // increasing X.
106        float[] v = new float[2];
107        v[0] = FloatMath.sin(angleRadians);
108        v[1] = -FloatMath.cos(angleRadians);
109        m.mapVectors(v);
110
111        // Derive the transformed vector's clockwise angle from vertical.
112        float result = (float) Math.atan2(v[0], -v[1]);
113        if (result < -Math.PI / 2) {
114            result += Math.PI;
115        } else if (result > Math.PI / 2) {
116            result -= Math.PI;
117        }
118        return result;
119    }
120}
121