Implement pointer acceleration.
Bug: 4124987
Change-Id: I1f31a28f1594c55302ccabe13fe3ca6d2ff71d50
diff --git a/include/ui/Input.h b/include/ui/Input.h
index fb6152e..d603441 100644
--- a/include/ui/Input.h
+++ b/include/ui/Input.h
@@ -627,6 +627,87 @@
int32_t mActivePointerId;
};
+
+/*
+ * 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;
+};
+
+
/*
* Describes the characteristics and capabilities of an input device.
*/