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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