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 */
16
17#define LOG_TAG "VelocityControl"
18//#define LOG_NDEBUG 0
19
20// Log debug messages about acceleration.
21#define DEBUG_ACCELERATION 0
22
23#include <math.h>
24#include <limits.h>
25
26#include <input/VelocityControl.h>
27#include <utils/BitSet.h>
28#include <utils/Timers.h>
29
30namespace android {
31
32// --- VelocityControl ---
33
34const nsecs_t VelocityControl::STOP_TIME;
35
36VelocityControl::VelocityControl() {
37    reset();
38}
39
40void VelocityControl::setParameters(const VelocityControlParameters& parameters) {
41    mParameters = parameters;
42    reset();
43}
44
45void VelocityControl::reset() {
46    mLastMovementTime = LLONG_MIN;
47    mRawPosition.x = 0;
48    mRawPosition.y = 0;
49    mVelocityTracker.clear();
50}
51
52void VelocityControl::move(nsecs_t eventTime, float* deltaX, float* deltaY) {
53    if ((deltaX && *deltaX) || (deltaY && *deltaY)) {
54        if (eventTime >= mLastMovementTime + STOP_TIME) {
55#if DEBUG_ACCELERATION
56            ALOGD("VelocityControl: stopped, last movement was %0.3fms ago",
57                    (eventTime - mLastMovementTime) * 0.000001f);
58#endif
59            reset();
60        }
61
62        mLastMovementTime = eventTime;
63        if (deltaX) {
64            mRawPosition.x += *deltaX;
65        }
66        if (deltaY) {
67            mRawPosition.y += *deltaY;
68        }
69        mVelocityTracker.addMovement(eventTime, BitSet32(BitSet32::valueForBit(0)), &mRawPosition);
70
71        float vx, vy;
72        float scale = mParameters.scale;
73        if (mVelocityTracker.getVelocity(0, &vx, &vy)) {
74            float speed = hypotf(vx, vy) * scale;
75            if (speed >= mParameters.highThreshold) {
76                // Apply full acceleration above the high speed threshold.
77                scale *= mParameters.acceleration;
78            } else if (speed > mParameters.lowThreshold) {
79                // Linearly interpolate the acceleration to apply between the low and high
80                // speed thresholds.
81                scale *= 1 + (speed - mParameters.lowThreshold)
82                        / (mParameters.highThreshold - mParameters.lowThreshold)
83                        * (mParameters.acceleration - 1);
84            }
85
86#if DEBUG_ACCELERATION
87            ALOGD("VelocityControl(%0.3f, %0.3f, %0.3f, %0.3f): "
88                    "vx=%0.3f, vy=%0.3f, speed=%0.3f, accel=%0.3f",
89                    mParameters.scale, mParameters.lowThreshold, mParameters.highThreshold,
90                    mParameters.acceleration,
91                    vx, vy, speed, scale / mParameters.scale);
92#endif
93        } else {
94#if DEBUG_ACCELERATION
95            ALOGD("VelocityControl(%0.3f, %0.3f, %0.3f, %0.3f): unknown velocity",
96                    mParameters.scale, mParameters.lowThreshold, mParameters.highThreshold,
97                    mParameters.acceleration);
98#endif
99        }
100
101        if (deltaX) {
102            *deltaX *= scale;
103        }
104        if (deltaY) {
105            *deltaY *= scale;
106        }
107    }
108}
109
110} // namespace android
111