108 lines
3.7 KiB
C
108 lines
3.7 KiB
C
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/*
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef _LIBINPUT_VELOCITY_CONTROL_H
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#define _LIBINPUT_VELOCITY_CONTROL_H
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#include <input/Input.h>
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#include <input/VelocityTracker.h>
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#include <utils/Timers.h>
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namespace android {
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/*
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* Specifies parameters that govern pointer or wheel acceleration.
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*/
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struct VelocityControlParameters {
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// A scale factor that is multiplied with the raw velocity deltas
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// prior to applying any other velocity control factors. The scale
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// factor should be used to adapt the input device resolution
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// (eg. counts per inch) to the output device resolution (eg. pixels per inch).
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//
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// Must be a positive value.
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// Default is 1.0 (no scaling).
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float scale;
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// The scaled speed at which acceleration begins to be applied.
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// This value establishes the upper bound of a low speed regime for
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// small precise motions that are performed without any acceleration.
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//
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// Must be a non-negative value.
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// Default is 0.0 (no low threshold).
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float lowThreshold;
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// The scaled speed at which maximum acceleration is applied.
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// The difference between highThreshold and lowThreshold controls
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// the range of speeds over which the acceleration factor is interpolated.
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// The wider the range, the smoother the acceleration.
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//
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// Must be a non-negative value greater than or equal to lowThreshold.
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// Default is 0.0 (no high threshold).
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float highThreshold;
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// The acceleration factor.
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// When the speed is above the low speed threshold, the velocity will scaled
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// by an interpolated value between 1.0 and this amount.
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//
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// Must be a positive greater than or equal to 1.0.
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// Default is 1.0 (no acceleration).
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float acceleration;
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VelocityControlParameters() :
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scale(1.0f), lowThreshold(0.0f), highThreshold(0.0f), acceleration(1.0f) {
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}
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VelocityControlParameters(float scale, float lowThreshold,
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float highThreshold, float acceleration) :
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scale(scale), lowThreshold(lowThreshold),
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highThreshold(highThreshold), acceleration(acceleration) {
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}
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};
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/*
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* Implements mouse pointer and wheel speed control and acceleration.
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*/
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class VelocityControl {
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public:
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VelocityControl();
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/* Sets the various parameters. */
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void setParameters(const VelocityControlParameters& parameters);
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/* Resets the current movement counters to zero.
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* This has the effect of nullifying any acceleration. */
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void reset();
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/* Translates a raw movement delta into an appropriately
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* scaled / accelerated delta based on the current velocity. */
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void move(nsecs_t eventTime, float* deltaX, float* deltaY);
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private:
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// If no movements are received within this amount of time,
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// we assume the movement has stopped and reset the movement counters.
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static const nsecs_t STOP_TIME = 500 * 1000000; // 500 ms
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VelocityControlParameters mParameters;
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nsecs_t mLastMovementTime;
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VelocityTracker::Position mRawPosition;
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VelocityTracker mVelocityTracker;
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};
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} // namespace android
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#endif // _LIBINPUT_VELOCITY_CONTROL_H
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