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