michael@0: /*
michael@0:  * Copyright (C) 2012 The Android Open Source Project
michael@0:  *
michael@0:  * Licensed under the Apache License, Version 2.0 (the "License");
michael@0:  * you may not use this file except in compliance with the License.
michael@0:  * You may obtain a copy of the License at
michael@0:  *
michael@0:  *      http://www.apache.org/licenses/LICENSE-2.0
michael@0:  *
michael@0:  * Unless required by applicable law or agreed to in writing, software
michael@0:  * distributed under the License is distributed on an "AS IS" BASIS,
michael@0:  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
michael@0:  * See the License for the specific language governing permissions and
michael@0:  * limitations under the License.
michael@0:  */
michael@0: 
michael@0: #define LOG_TAG "VelocityControl"
michael@0: //#define LOG_NDEBUG 0
michael@0: 
michael@0: // Log debug messages about acceleration.
michael@0: #define DEBUG_ACCELERATION 0
michael@0: 
michael@0: #include <math.h>
michael@0: #include <limits.h>
michael@0: 
michael@0: #include "VelocityControl.h"
michael@0: #include <utils/BitSet.h>
michael@0: #include <utils/Timers.h>
michael@0: 
michael@0: namespace android {
michael@0: 
michael@0: // --- VelocityControl ---
michael@0: 
michael@0: const nsecs_t VelocityControl::STOP_TIME;
michael@0: 
michael@0: VelocityControl::VelocityControl() {
michael@0:     reset();
michael@0: }
michael@0: 
michael@0: void VelocityControl::setParameters(const VelocityControlParameters& parameters) {
michael@0:     mParameters = parameters;
michael@0:     reset();
michael@0: }
michael@0: 
michael@0: void VelocityControl::reset() {
michael@0:     mLastMovementTime = LLONG_MIN;
michael@0:     mRawPosition.x = 0;
michael@0:     mRawPosition.y = 0;
michael@0:     mVelocityTracker.clear();
michael@0: }
michael@0: 
michael@0: void VelocityControl::move(nsecs_t eventTime, float* deltaX, float* deltaY) {
michael@0:     if ((deltaX && *deltaX) || (deltaY && *deltaY)) {
michael@0:         if (eventTime >= mLastMovementTime + STOP_TIME) {
michael@0: #if DEBUG_ACCELERATION
michael@0:             ALOGD("VelocityControl: stopped, last movement was %0.3fms ago",
michael@0:                     (eventTime - mLastMovementTime) * 0.000001f);
michael@0: #endif
michael@0:             reset();
michael@0:         }
michael@0: 
michael@0:         mLastMovementTime = eventTime;
michael@0:         if (deltaX) {
michael@0:             mRawPosition.x += *deltaX;
michael@0:         }
michael@0:         if (deltaY) {
michael@0:             mRawPosition.y += *deltaY;
michael@0:         }
michael@0:         mVelocityTracker.addMovement(eventTime, BitSet32(BitSet32::valueForBit(0)), &mRawPosition);
michael@0: 
michael@0:         float vx, vy;
michael@0:         float scale = mParameters.scale;
michael@0:         if (mVelocityTracker.getVelocity(0, &vx, &vy)) {
michael@0:             float speed = hypotf(vx, vy) * scale;
michael@0:             if (speed >= mParameters.highThreshold) {
michael@0:                 // Apply full acceleration above the high speed threshold.
michael@0:                 scale *= mParameters.acceleration;
michael@0:             } else if (speed > mParameters.lowThreshold) {
michael@0:                 // Linearly interpolate the acceleration to apply between the low and high
michael@0:                 // speed thresholds.
michael@0:                 scale *= 1 + (speed - mParameters.lowThreshold)
michael@0:                         / (mParameters.highThreshold - mParameters.lowThreshold)
michael@0:                         * (mParameters.acceleration - 1);
michael@0:             }
michael@0: 
michael@0: #if DEBUG_ACCELERATION
michael@0:             ALOGD("VelocityControl(%0.3f, %0.3f, %0.3f, %0.3f): "
michael@0:                     "vx=%0.3f, vy=%0.3f, speed=%0.3f, accel=%0.3f",
michael@0:                     mParameters.scale, mParameters.lowThreshold, mParameters.highThreshold,
michael@0:                     mParameters.acceleration,
michael@0:                     vx, vy, speed, scale / mParameters.scale);
michael@0: #endif
michael@0:         } else {
michael@0: #if DEBUG_ACCELERATION
michael@0:             ALOGD("VelocityControl(%0.3f, %0.3f, %0.3f, %0.3f): unknown velocity",
michael@0:                     mParameters.scale, mParameters.lowThreshold, mParameters.highThreshold,
michael@0:                     mParameters.acceleration);
michael@0: #endif
michael@0:         }
michael@0: 
michael@0:         if (deltaX) {
michael@0:             *deltaX *= scale;
michael@0:         }
michael@0:         if (deltaY) {
michael@0:             *deltaY *= scale;
michael@0:         }
michael@0:     }
michael@0: }
michael@0: 
michael@0: } // namespace android