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: #ifndef _ANDROIDFW_VELOCITY_CONTROL_H
michael@0: #define _ANDROIDFW_VELOCITY_CONTROL_H
michael@0: 
michael@0: #include "Input.h"
michael@0: #include "VelocityTracker.h"
michael@0: #include <utils/Timers.h>
michael@0: 
michael@0: namespace android {
michael@0: 
michael@0: /*
michael@0:  * Specifies parameters that govern pointer or wheel acceleration.
michael@0:  */
michael@0: struct VelocityControlParameters {
michael@0:     // A scale factor that is multiplied with the raw velocity deltas
michael@0:     // prior to applying any other velocity control factors.  The scale
michael@0:     // factor should be used to adapt the input device resolution
michael@0:     // (eg. counts per inch) to the output device resolution (eg. pixels per inch).
michael@0:     //
michael@0:     // Must be a positive value.
michael@0:     // Default is 1.0 (no scaling).
michael@0:     float scale;
michael@0: 
michael@0:     // The scaled speed at which acceleration begins to be applied.
michael@0:     // This value establishes the upper bound of a low speed regime for
michael@0:     // small precise motions that are performed without any acceleration.
michael@0:     //
michael@0:     // Must be a non-negative value.
michael@0:     // Default is 0.0 (no low threshold).
michael@0:     float lowThreshold;
michael@0: 
michael@0:     // The scaled speed at which maximum acceleration is applied.
michael@0:     // The difference between highThreshold and lowThreshold controls
michael@0:     // the range of speeds over which the acceleration factor is interpolated.
michael@0:     // The wider the range, the smoother the acceleration.
michael@0:     //
michael@0:     // Must be a non-negative value greater than or equal to lowThreshold.
michael@0:     // Default is 0.0 (no high threshold).
michael@0:     float highThreshold;
michael@0: 
michael@0:     // The acceleration factor.
michael@0:     // When the speed is above the low speed threshold, the velocity will scaled
michael@0:     // by an interpolated value between 1.0 and this amount.
michael@0:     //
michael@0:     // Must be a positive greater than or equal to 1.0.
michael@0:     // Default is 1.0 (no acceleration).
michael@0:     float acceleration;
michael@0: 
michael@0:     VelocityControlParameters() :
michael@0:             scale(1.0f), lowThreshold(0.0f), highThreshold(0.0f), acceleration(1.0f) {
michael@0:     }
michael@0: 
michael@0:     VelocityControlParameters(float scale, float lowThreshold,
michael@0:             float highThreshold, float acceleration) :
michael@0:             scale(scale), lowThreshold(lowThreshold),
michael@0:             highThreshold(highThreshold), acceleration(acceleration) {
michael@0:     }
michael@0: };
michael@0: 
michael@0: /*
michael@0:  * Implements mouse pointer and wheel speed control and acceleration.
michael@0:  */
michael@0: class VelocityControl {
michael@0: public:
michael@0:     VelocityControl();
michael@0: 
michael@0:     /* Sets the various parameters. */
michael@0:     void setParameters(const VelocityControlParameters& parameters);
michael@0: 
michael@0:     /* Resets the current movement counters to zero.
michael@0:      * This has the effect of nullifying any acceleration. */
michael@0:     void reset();
michael@0: 
michael@0:     /* Translates a raw movement delta into an appropriately
michael@0:      * scaled / accelerated delta based on the current velocity. */
michael@0:     void move(nsecs_t eventTime, float* deltaX, float* deltaY);
michael@0: 
michael@0: private:
michael@0:     // If no movements are received within this amount of time,
michael@0:     // we assume the movement has stopped and reset the movement counters.
michael@0:     static const nsecs_t STOP_TIME = 500 * 1000000; // 500 ms
michael@0: 
michael@0:     VelocityControlParameters mParameters;
michael@0: 
michael@0:     nsecs_t mLastMovementTime;
michael@0:     VelocityTracker::Position mRawPosition;
michael@0:     VelocityTracker mVelocityTracker;
michael@0: };
michael@0: 
michael@0: } // namespace android
michael@0: 
michael@0: #endif // _ANDROIDFW_VELOCITY_CONTROL_H