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 /*

  * Copyright (C) 2012 The Android Open Source Project

  *

  * Licensed under the Apache License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  *

  *      http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 #ifndef _ANDROIDFW_VELOCITY_CONTROL_H

 #define _ANDROIDFW_VELOCITY_CONTROL_H

 #include "Input.h"

 #include "VelocityTracker.h"

 #include <utils/Timers.h>

 namespace android {

 /*

  * Specifies parameters that govern pointer or wheel acceleration.

  */

 struct VelocityControlParameters {

     // A scale factor that is multiplied with the raw velocity deltas

     // prior to applying any other velocity control factors.  The scale

     // factor should be used to adapt the input device resolution

     // (eg. counts per inch) to the output device resolution (eg. pixels per inch).

     //

     // Must be a positive value.

     // Default is 1.0 (no scaling).

     float scale;

     // The scaled speed at which acceleration begins to be applied.

     // This value establishes the upper bound of a low speed regime for

     // small precise motions that are performed without any acceleration.

     //

     // Must be a non-negative value.

     // Default is 0.0 (no low threshold).

     float lowThreshold;

     // The scaled speed at which maximum acceleration is applied.

     // The difference between highThreshold and lowThreshold controls

     // the range of speeds over which the acceleration factor is interpolated.

     // The wider the range, the smoother the acceleration.

     //

     // Must be a non-negative value greater than or equal to lowThreshold.

     // Default is 0.0 (no high threshold).

     float highThreshold;

     // The acceleration factor.

     // When the speed is above the low speed threshold, the velocity will scaled

     // by an interpolated value between 1.0 and this amount.

     //

     // Must be a positive greater than or equal to 1.0.

     // Default is 1.0 (no acceleration).

     float acceleration;

     VelocityControlParameters() :

             scale(1.0f), lowThreshold(0.0f), highThreshold(0.0f), acceleration(1.0f) {

     }

     VelocityControlParameters(float scale, float lowThreshold,

             float highThreshold, float acceleration) :

             scale(scale), lowThreshold(lowThreshold),

             highThreshold(highThreshold), acceleration(acceleration) {

     }

 };

 /*

  * Implements mouse pointer and wheel speed control and acceleration.

  */

 class VelocityControl {

 public:

     VelocityControl();

     /* Sets the various parameters. */

     void setParameters(const VelocityControlParameters& parameters);

     /* Resets the current movement counters to zero.

      * This has the effect of nullifying any acceleration. */

     void reset();

     /* Translates a raw movement delta into an appropriately

      * scaled / accelerated delta based on the current velocity. */

     void move(nsecs_t eventTime, float* deltaX, float* deltaY);

 private:

     // If no movements are received within this amount of time,

     // we assume the movement has stopped and reset the movement counters.

     static const nsecs_t STOP_TIME = 500 * 1000000; // 500 ms

     VelocityControlParameters mParameters;

     nsecs_t mLastMovementTime;

     VelocityTracker::Position mRawPosition;

     VelocityTracker mVelocityTracker;

 };

 } // namespace android

 #endif // _ANDROIDFW_VELOCITY_CONTROL_H