From adab62038365be512aa9c21cf64df642dd075704 Mon Sep 17 00:00:00 2001
From: Jeff Brown <jeffbrown@android.com>
Date: Wed, 1 Jun 2011 12:33:19 -0700
Subject: Implement pointer acceleration.

Bug: 4124987
Change-Id: I1f31a28f1594c55302ccabe13fe3ca6d2ff71d50
---
 include/ui/Input.h | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

(limited to 'include/ui')

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 @@ private:
     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.
  */
-- 
cgit v1.1