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 #ifndef _LIBINPUT_VELOCITY_CONTROL_H 18 #define _LIBINPUT_VELOCITY_CONTROL_H 19 20 #include <input/Input.h> 21 #include <input/VelocityTracker.h> 22 #include <utils/Timers.h> 23 24 namespace android { 25 26 /* 27 * Specifies parameters that govern pointer or wheel acceleration. 28 */ 29 struct VelocityControlParameters { 30 // A scale factor that is multiplied with the raw velocity deltas 31 // prior to applying any other velocity control factors. The scale 32 // factor should be used to adapt the input device resolution 33 // (eg. counts per inch) to the output device resolution (eg. pixels per inch). 34 // 35 // Must be a positive value. 36 // Default is 1.0 (no scaling). 37 float scale; 38 39 // The scaled speed at which acceleration begins to be applied. 40 // This value establishes the upper bound of a low speed regime for 41 // small precise motions that are performed without any acceleration. 42 // 43 // Must be a non-negative value. 44 // Default is 0.0 (no low threshold). 45 float lowThreshold; 46 47 // The scaled speed at which maximum acceleration is applied. 48 // The difference between highThreshold and lowThreshold controls 49 // the range of speeds over which the acceleration factor is interpolated. 50 // The wider the range, the smoother the acceleration. 51 // 52 // Must be a non-negative value greater than or equal to lowThreshold. 53 // Default is 0.0 (no high threshold). 54 float highThreshold; 55 56 // The acceleration factor. 57 // When the speed is above the low speed threshold, the velocity will scaled 58 // by an interpolated value between 1.0 and this amount. 59 // 60 // Must be a positive greater than or equal to 1.0. 61 // Default is 1.0 (no acceleration). 62 float acceleration; 63 VelocityControlParametersVelocityControlParameters64 VelocityControlParameters() : 65 scale(1.0f), lowThreshold(0.0f), highThreshold(0.0f), acceleration(1.0f) { 66 } 67 VelocityControlParametersVelocityControlParameters68 VelocityControlParameters(float scale, float lowThreshold, 69 float highThreshold, float acceleration) : 70 scale(scale), lowThreshold(lowThreshold), 71 highThreshold(highThreshold), acceleration(acceleration) { 72 } 73 }; 74 75 /* 76 * Implements mouse pointer and wheel speed control and acceleration. 77 */ 78 class VelocityControl { 79 public: 80 VelocityControl(); 81 82 /* Sets the various parameters. */ 83 void setParameters(const VelocityControlParameters& parameters); 84 85 /* Resets the current movement counters to zero. 86 * This has the effect of nullifying any acceleration. */ 87 void reset(); 88 89 /* Translates a raw movement delta into an appropriately 90 * scaled / accelerated delta based on the current velocity. */ 91 void move(nsecs_t eventTime, float* deltaX, float* deltaY); 92 93 private: 94 // If no movements are received within this amount of time, 95 // we assume the movement has stopped and reset the movement counters. 96 static const nsecs_t STOP_TIME = 500 * 1000000; // 500 ms 97 98 VelocityControlParameters mParameters; 99 100 nsecs_t mLastMovementTime; 101 VelocityTracker::Position mRawPosition; 102 VelocityTracker mVelocityTracker; 103 }; 104 105 } // namespace android 106 107 #endif // _LIBINPUT_VELOCITY_CONTROL_H 108