Implement pointer acceleration.

Bug: 4124987
Change-Id: I1f31a28f1594c55302ccabe13fe3ca6d2ff71d50

libs/ui/Input.cpp

@@ -13,6 +13,10 @@
 // Log debug messages about velocity tracking.
 #define DEBUG_VELOCITY 0
 
+// Log debug messages about acceleration.
+#define DEBUG_ACCELERATION 0
+
+
 #include <stdlib.h>
 #include <unistd.h>
 #include <ctype.h>
@@ -20,6 +24,7 @@
 #include <ui/Input.h>
 
 #include <math.h>
+#include <limits.h>
 
 #ifdef HAVE_ANDROID_OS
 #include <binder/Parcel.h>
@@ -670,6 +675,11 @@ bool MotionEvent::isTouchEvent(int32_t source, int32_t action) {
 
 // --- VelocityTracker ---
 
+const uint32_t VelocityTracker::HISTORY_SIZE;
+const nsecs_t VelocityTracker::MAX_AGE;
+const nsecs_t VelocityTracker::MIN_WINDOW;
+const nsecs_t VelocityTracker::MIN_DURATION;
+
 VelocityTracker::VelocityTracker() {
     clear();
 }
@@ -879,6 +889,85 @@ bool VelocityTracker::getVelocity(uint32_t id, float* outVx, float* outVy) const
 }
 
 
+// --- VelocityControl ---
+
+const nsecs_t VelocityControl::STOP_TIME;
+
+VelocityControl::VelocityControl() {
+    reset();
+}
+
+void VelocityControl::setParameters(const VelocityControlParameters& parameters) {
+    mParameters = parameters;
+    reset();
+}
+
+void VelocityControl::reset() {
+    mLastMovementTime = LLONG_MIN;
+    mRawPosition.x = 0;
+    mRawPosition.y = 0;
+    mVelocityTracker.clear();
+}
+
+void VelocityControl::move(nsecs_t eventTime, float* deltaX, float* deltaY) {
+    if ((deltaX && *deltaX) || (deltaY && *deltaY)) {
+        if (eventTime >= mLastMovementTime + STOP_TIME) {
+#if DEBUG_ACCELERATION
+            LOGD("VelocityControl: stopped, last movement was %0.3fms ago",
+                    (eventTime - mLastMovementTime) * 0.000001f);
+#endif
+            reset();
+        }
+
+        mLastMovementTime = eventTime;
+        if (deltaX) {
+            mRawPosition.x += *deltaX;
+        }
+        if (deltaY) {
+            mRawPosition.y += *deltaY;
+        }
+        mVelocityTracker.addMovement(eventTime, BitSet32(BitSet32::valueForBit(0)), &mRawPosition);
+
+        float vx, vy;
+        float scale = mParameters.scale;
+        if (mVelocityTracker.getVelocity(0, &vx, &vy)) {
+            float speed = hypotf(vx, vy) * scale;
+            if (speed >= mParameters.highThreshold) {
+                // Apply full acceleration above the high speed threshold.
+                scale *= mParameters.acceleration;
+            } else if (speed > mParameters.lowThreshold) {
+                // Linearly interpolate the acceleration to apply between the low and high
+                // speed thresholds.
+                scale *= 1 + (speed - mParameters.lowThreshold)
+                        / (mParameters.highThreshold - mParameters.lowThreshold)
+                        * (mParameters.acceleration - 1);
+            }
+
+#if DEBUG_ACCELERATION
+            LOGD("VelocityControl(%0.3f, %0.3f, %0.3f, %0.3f): "
+                    "vx=%0.3f, vy=%0.3f, speed=%0.3f, accel=%0.3f",
+                    mParameters.scale, mParameters.lowThreshold, mParameters.highThreshold,
+                    mParameters.acceleration,
+                    vx, vy, speed, scale / mParameters.scale);
+#endif
+        } else {
+#if DEBUG_ACCELERATION
+            LOGD("VelocityControl(%0.3f, %0.3f, %0.3f, %0.3f): unknown velocity",
+                    mParameters.scale, mParameters.lowThreshold, mParameters.highThreshold,
+                    mParameters.acceleration);
+#endif
+        }
+
+        if (deltaX) {
+            *deltaX *= scale;
+        }
+        if (deltaY) {
+            *deltaY *= scale;
+        }
+    }
+}
+
+
 // --- InputDeviceInfo ---
 
 InputDeviceInfo::InputDeviceInfo() {