Using platform implementation of Scroller instead of maintaining a copy

Bug: 109828536
Change-Id: Ief98c96e0c39a2ea70ed32e59aff71e6c45b176a
diff --git a/src/com/android/launcher3/LauncherScroller.java b/src/com/android/launcher3/LauncherScroller.java
index a9b4955..e5042c4 100644
--- a/src/com/android/launcher3/LauncherScroller.java
+++ b/src/com/android/launcher3/LauncherScroller.java
@@ -18,541 +18,37 @@
 
 import android.animation.TimeInterpolator;
 import android.content.Context;
-import android.hardware.SensorManager;
-import android.os.Build;
-import android.view.ViewConfiguration;
-import android.view.animation.AnimationUtils;
 import android.view.animation.Interpolator;
+import android.widget.Scroller;
 
 /**
- * This class differs from the framework {@link android.widget.Scroller} in that
- * you can modify the Interpolator post-construction.
+ * Extension of {@link android.widget.Scroller} with the ability to modify the
+ * Interpolator post-construction.
  */
-public class LauncherScroller  {
-    private int mMode;
+public class LauncherScroller extends Scroller {
 
-    private int mStartX;
-    private int mStartY;
-    private int mFinalX;
-    private int mFinalY;
+    private final InterpolatorWrapper mInterpolatorWrapper;
 
-    private int mMinX;
-    private int mMaxX;
-    private int mMinY;
-    private int mMaxY;
-
-    private int mCurrX;
-    private int mCurrY;
-    private long mStartTime;
-    private int mDuration;
-    private float mDurationReciprocal;
-    private float mDeltaX;
-    private float mDeltaY;
-    private boolean mFinished;
-    private TimeInterpolator mInterpolator;
-    private boolean mFlywheel;
-
-    private float mVelocity;
-    private float mCurrVelocity;
-    private int mDistance;
-
-    private float mFlingFriction = ViewConfiguration.getScrollFriction();
-
-    private static final int DEFAULT_DURATION = 250;
-    private static final int SCROLL_MODE = 0;
-    private static final int FLING_MODE = 1;
-
-    private static float DECELERATION_RATE = (float) (Math.log(0.78) / Math.log(0.9));
-    private static final float INFLEXION = 0.35f; // Tension lines cross at (INFLEXION, 1)
-    private static final float START_TENSION = 0.5f;
-    private static final float END_TENSION = 1.0f;
-    private static final float P1 = START_TENSION * INFLEXION;
-    private static final float P2 = 1.0f - END_TENSION * (1.0f - INFLEXION);
-
-    private static final int NB_SAMPLES = 100;
-    private static final float[] SPLINE_POSITION = new float[NB_SAMPLES + 1];
-    private static final float[] SPLINE_TIME = new float[NB_SAMPLES + 1];
-
-    private float mDeceleration;
-    private final float mPpi;
-
-    // A context-specific coefficient adjusted to physical values.
-    private float mPhysicalCoeff;
-
-    static {
-        float x_min = 0.0f;
-        float y_min = 0.0f;
-        for (int i = 0; i < NB_SAMPLES; i++) {
-            final float alpha = (float) i / NB_SAMPLES;
-
-            float x_max = 1.0f;
-            float x, tx, coef;
-            while (true) {
-                x = x_min + (x_max - x_min) / 2.0f;
-                coef = 3.0f * x * (1.0f - x);
-                tx = coef * ((1.0f - x) * P1 + x * P2) + x * x * x;
-                if (Math.abs(tx - alpha) < 1E-5) break;
-                if (tx > alpha) x_max = x;
-                else x_min = x;
-            }
-            SPLINE_POSITION[i] = coef * ((1.0f - x) * START_TENSION + x) + x * x * x;
-
-            float y_max = 1.0f;
-            float y, dy;
-            while (true) {
-                y = y_min + (y_max - y_min) / 2.0f;
-                coef = 3.0f * y * (1.0f - y);
-                dy = coef * ((1.0f - y) * START_TENSION + y) + y * y * y;
-                if (Math.abs(dy - alpha) < 1E-5) break;
-                if (dy > alpha) y_max = y;
-                else y_min = y;
-            }
-            SPLINE_TIME[i] = coef * ((1.0f - y) * P1 + y * P2) + y * y * y;
-        }
-        SPLINE_POSITION[NB_SAMPLES] = SPLINE_TIME[NB_SAMPLES] = 1.0f;
-
-        // This controls the viscous fluid effect (how much of it)
-        sViscousFluidScale = 8.0f;
-        // must be set to 1.0 (used in viscousFluid())
-        sViscousFluidNormalize = 1.0f;
-        sViscousFluidNormalize = 1.0f / viscousFluid(1.0f);
-
+    public LauncherScroller(Context context) {
+        this(context, new InterpolatorWrapper());
     }
 
-    private static float sViscousFluidScale;
-    private static float sViscousFluidNormalize;
+    private LauncherScroller(Context context, InterpolatorWrapper interpolatorWrapper) {
+        super(context, interpolatorWrapper);
+        mInterpolatorWrapper = interpolatorWrapper;
+    }
 
     public void setInterpolator(TimeInterpolator interpolator) {
-        mInterpolator = interpolator;
+        mInterpolatorWrapper.interpolator = interpolator;
     }
 
-    /**
-     * Create a Scroller with the default duration and interpolator.
-     */
-    public LauncherScroller(Context context) {
-        this(context, null);
-    }
+    private static class InterpolatorWrapper implements Interpolator {
 
-    /**
-     * Create a Scroller with the specified interpolator. If the interpolator is
-     * null, the default (viscous) interpolator will be used. "Flywheel" behavior will
-     * be in effect for apps targeting Honeycomb or newer.
-     */
-    public LauncherScroller(Context context, Interpolator interpolator) {
-        this(context, interpolator,
-                context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB);
-    }
+        public TimeInterpolator interpolator;
 
-    /**
-     * Create a Scroller with the specified interpolator. If the interpolator is
-     * null, the default (viscous) interpolator will be used. Specify whether or
-     * not to support progressive "flywheel" behavior in flinging.
-     */
-    public LauncherScroller(Context context, Interpolator interpolator, boolean flywheel) {
-        mFinished = true;
-        mInterpolator = interpolator;
-        mPpi = context.getResources().getDisplayMetrics().density * 160.0f;
-        mDeceleration = computeDeceleration(ViewConfiguration.getScrollFriction());
-        mFlywheel = flywheel;
-
-        mPhysicalCoeff = computeDeceleration(0.84f); // look and feel tuning
-    }
-
-    /**
-     * The amount of friction applied to flings. The default value
-     * is {@link ViewConfiguration#getScrollFriction}.
-     *
-     * @param friction A scalar dimension-less value representing the coefficient of
-     *         friction.
-     */
-    public final void setFriction(float friction) {
-        mDeceleration = computeDeceleration(friction);
-        mFlingFriction = friction;
-    }
-
-    private float computeDeceleration(float friction) {
-        return SensorManager.GRAVITY_EARTH   // g (m/s^2)
-                      * 39.37f               // inch/meter
-                      * mPpi                 // pixels per inch
-                      * friction;
-    }
-
-    /**
-     *
-     * Returns whether the scroller has finished scrolling.
-     *
-     * @return True if the scroller has finished scrolling, false otherwise.
-     */
-    public final boolean isFinished() {
-        return mFinished;
-    }
-
-    /**
-     * Force the finished field to a particular value.
-     *
-     * @param finished The new finished value.
-     */
-    public final void forceFinished(boolean finished) {
-        mFinished = finished;
-    }
-
-    /**
-     * Returns how long the scroll event will take, in milliseconds.
-     *
-     * @return The duration of the scroll in milliseconds.
-     */
-    public final int getDuration() {
-        return mDuration;
-    }
-
-    /**
-     * Returns the current X offset in the scroll.
-     *
-     * @return The new X offset as an absolute distance from the origin.
-     */
-    public final int getCurrX() {
-        return mCurrX;
-    }
-
-    /**
-     * Returns the current Y offset in the scroll.
-     *
-     * @return The new Y offset as an absolute distance from the origin.
-     */
-    public final int getCurrY() {
-        return mCurrY;
-    }
-
-    /**
-     * Returns the current velocity.
-     *
-     * @return The original velocity less the deceleration. Result may be
-     * negative.
-     */
-    public float getCurrVelocity() {
-        return mMode == FLING_MODE ?
-                mCurrVelocity : mVelocity - mDeceleration * timePassed() / 2000.0f;
-    }
-
-    /**
-     * Returns the start X offset in the scroll.
-     *
-     * @return The start X offset as an absolute distance from the origin.
-     */
-    public final int getStartX() {
-        return mStartX;
-    }
-
-    /**
-     * Returns the start Y offset in the scroll.
-     *
-     * @return The start Y offset as an absolute distance from the origin.
-     */
-    public final int getStartY() {
-        return mStartY;
-    }
-
-    /**
-     * Returns where the scroll will end. Valid only for "fling" scrolls.
-     *
-     * @return The final X offset as an absolute distance from the origin.
-     */
-    public final int getFinalX() {
-        return mFinalX;
-    }
-
-    /**
-     * Returns where the scroll will end. Valid only for "fling" scrolls.
-     *
-     * @return The final Y offset as an absolute distance from the origin.
-     */
-    public final int getFinalY() {
-        return mFinalY;
-    }
-
-    /**
-     * Call this when you want to know the new location.  If it returns true,
-     * the animation is not yet finished.
-     */
-    public boolean computeScrollOffset() {
-        if (mFinished) {
-            return false;
+        @Override
+        public float getInterpolation(float v) {
+            return interpolator == null ? v : interpolator.getInterpolation(v);
         }
-
-        int timePassed = (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
-
-        if (timePassed < mDuration) {
-            switch (mMode) {
-            case SCROLL_MODE:
-                float x = timePassed * mDurationReciprocal;
-
-                if (mInterpolator == null)
-                    x = viscousFluid(x);
-                else
-                    x = mInterpolator.getInterpolation(x);
-
-                mCurrX = mStartX + Math.round(x * mDeltaX);
-                mCurrY = mStartY + Math.round(x * mDeltaY);
-                break;
-            case FLING_MODE:
-                final float t = (float) timePassed / mDuration;
-                final int index = (int) (NB_SAMPLES * t);
-                float distanceCoef = 1.f;
-                float velocityCoef = 0.f;
-                if (index < NB_SAMPLES) {
-                    final float t_inf = (float) index / NB_SAMPLES;
-                    final float t_sup = (float) (index + 1) / NB_SAMPLES;
-                    final float d_inf = SPLINE_POSITION[index];
-                    final float d_sup = SPLINE_POSITION[index + 1];
-                    velocityCoef = (d_sup - d_inf) / (t_sup - t_inf);
-                    distanceCoef = d_inf + (t - t_inf) * velocityCoef;
-                }
-
-                mCurrVelocity = velocityCoef * mDistance / mDuration * 1000.0f;
-
-                mCurrX = mStartX + Math.round(distanceCoef * (mFinalX - mStartX));
-                // Pin to mMinX <= mCurrX <= mMaxX
-                mCurrX = Math.min(mCurrX, mMaxX);
-                mCurrX = Math.max(mCurrX, mMinX);
-
-                mCurrY = mStartY + Math.round(distanceCoef * (mFinalY - mStartY));
-                // Pin to mMinY <= mCurrY <= mMaxY
-                mCurrY = Math.min(mCurrY, mMaxY);
-                mCurrY = Math.max(mCurrY, mMinY);
-
-                if (mCurrX == mFinalX && mCurrY == mFinalY) {
-                    mFinished = true;
-                }
-
-                break;
-            }
-        }
-        else {
-            mCurrX = mFinalX;
-            mCurrY = mFinalY;
-            mFinished = true;
-        }
-        return true;
-    }
-
-    /**
-     * Start scrolling by providing a starting point and the distance to travel.
-     * The scroll will use the default value of 250 milliseconds for the
-     * duration.
-     *
-     * @param startX Starting horizontal scroll offset in pixels. Positive
-     *        numbers will scroll the content to the left.
-     * @param startY Starting vertical scroll offset in pixels. Positive numbers
-     *        will scroll the content up.
-     * @param dx Horizontal distance to travel. Positive numbers will scroll the
-     *        content to the left.
-     * @param dy Vertical distance to travel. Positive numbers will scroll the
-     *        content up.
-     */
-    public void startScroll(int startX, int startY, int dx, int dy) {
-        startScroll(startX, startY, dx, dy, DEFAULT_DURATION);
-    }
-
-    /**
-     * Start scrolling by providing a starting point, the distance to travel,
-     * and the duration of the scroll.
-     *
-     * @param startX Starting horizontal scroll offset in pixels. Positive
-     *        numbers will scroll the content to the left.
-     * @param startY Starting vertical scroll offset in pixels. Positive numbers
-     *        will scroll the content up.
-     * @param dx Horizontal distance to travel. Positive numbers will scroll the
-     *        content to the left.
-     * @param dy Vertical distance to travel. Positive numbers will scroll the
-     *        content up.
-     * @param duration Duration of the scroll in milliseconds.
-     */
-    public void startScroll(int startX, int startY, int dx, int dy, int duration) {
-        mMode = SCROLL_MODE;
-        mFinished = false;
-        mDuration = duration;
-        mStartTime = AnimationUtils.currentAnimationTimeMillis();
-        mStartX = startX;
-        mStartY = startY;
-        mFinalX = startX + dx;
-        mFinalY = startY + dy;
-        mDeltaX = dx;
-        mDeltaY = dy;
-        mDurationReciprocal = 1.0f / (float) mDuration;
-    }
-
-    /**
-     * Start scrolling based on a fling gesture. The distance travelled will
-     * depend on the initial velocity of the fling.
-     *
-     * @param startX Starting point of the scroll (X)
-     * @param startY Starting point of the scroll (Y)
-     * @param velocityX Initial velocity of the fling (X) measured in pixels per
-     *        second.
-     * @param velocityY Initial velocity of the fling (Y) measured in pixels per
-     *        second
-     * @param minX Minimum X value. The scroller will not scroll past this
-     *        point.
-     * @param maxX Maximum X value. The scroller will not scroll past this
-     *        point.
-     * @param minY Minimum Y value. The scroller will not scroll past this
-     *        point.
-     * @param maxY Maximum Y value. The scroller will not scroll past this
-     *        point.
-     */
-    public void fling(int startX, int startY, int velocityX, int velocityY,
-            int minX, int maxX, int minY, int maxY) {
-        // Continue a scroll or fling in progress
-        if (mFlywheel && !mFinished) {
-            float oldVel = getCurrVelocity();
-
-            float dx = (float) (mFinalX - mStartX);
-            float dy = (float) (mFinalY - mStartY);
-            float hyp = (float) Math.hypot(dx, dy);
-
-            float ndx = dx / hyp;
-            float ndy = dy / hyp;
-
-            float oldVelocityX = ndx * oldVel;
-            float oldVelocityY = ndy * oldVel;
-            if (Math.signum(velocityX) == Math.signum(oldVelocityX) &&
-                    Math.signum(velocityY) == Math.signum(oldVelocityY)) {
-                velocityX += oldVelocityX;
-                velocityY += oldVelocityY;
-            }
-        }
-
-        mMode = FLING_MODE;
-        mFinished = false;
-
-        float velocity = (float) Math.hypot(velocityX, velocityY);
-
-        mVelocity = velocity;
-        mDuration = getSplineFlingDuration(velocity);
-        mStartTime = AnimationUtils.currentAnimationTimeMillis();
-        mStartX = startX;
-        mStartY = startY;
-
-        float coeffX = velocity == 0 ? 1.0f : velocityX / velocity;
-        float coeffY = velocity == 0 ? 1.0f : velocityY / velocity;
-
-        double totalDistance = getSplineFlingDistance(velocity);
-        mDistance = (int) (totalDistance * Math.signum(velocity));
-
-        mMinX = minX;
-        mMaxX = maxX;
-        mMinY = minY;
-        mMaxY = maxY;
-
-        mFinalX = startX + (int) Math.round(totalDistance * coeffX);
-        // Pin to mMinX <= mFinalX <= mMaxX
-        mFinalX = Math.min(mFinalX, mMaxX);
-        mFinalX = Math.max(mFinalX, mMinX);
-
-        mFinalY = startY + (int) Math.round(totalDistance * coeffY);
-        // Pin to mMinY <= mFinalY <= mMaxY
-        mFinalY = Math.min(mFinalY, mMaxY);
-        mFinalY = Math.max(mFinalY, mMinY);
-    }
-
-    private double getSplineDeceleration(float velocity) {
-        return Math.log(INFLEXION * Math.abs(velocity) / (mFlingFriction * mPhysicalCoeff));
-    }
-
-    private int getSplineFlingDuration(float velocity) {
-        final double l = getSplineDeceleration(velocity);
-        final double decelMinusOne = DECELERATION_RATE - 1.0;
-        return (int) (1000.0 * Math.exp(l / decelMinusOne));
-    }
-
-    private double getSplineFlingDistance(float velocity) {
-        final double l = getSplineDeceleration(velocity);
-        final double decelMinusOne = DECELERATION_RATE - 1.0;
-        return mFlingFriction * mPhysicalCoeff * Math.exp(DECELERATION_RATE / decelMinusOne * l);
-    }
-
-    static float viscousFluid(float x)
-    {
-        x *= sViscousFluidScale;
-        if (x < 1.0f) {
-            x -= (1.0f - (float)Math.exp(-x));
-        } else {
-            float start = 0.36787944117f;   // 1/e == exp(-1)
-            x = 1.0f - (float)Math.exp(1.0f - x);
-            x = start + x * (1.0f - start);
-        }
-        x *= sViscousFluidNormalize;
-        return x;
-    }
-
-    /**
-     * Stops the animation. Contrary to {@link #forceFinished(boolean)},
-     * aborting the animating cause the scroller to move to the final x and y
-     * position
-     *
-     * @see #forceFinished(boolean)
-     */
-    public void abortAnimation() {
-        mCurrX = mFinalX;
-        mCurrY = mFinalY;
-        mFinished = true;
-    }
-
-    /**
-     * Extend the scroll animation. This allows a running animation to scroll
-     * further and longer, when used with {@link #setFinalX(int)} or {@link #setFinalY(int)}.
-     *
-     * @param extend Additional time to scroll in milliseconds.
-     * @see #setFinalX(int)
-     * @see #setFinalY(int)
-     */
-    public void extendDuration(int extend) {
-        int passed = timePassed();
-        mDuration = passed + extend;
-        mDurationReciprocal = 1.0f / mDuration;
-        mFinished = false;
-    }
-
-    /**
-     * Returns the time elapsed since the beginning of the scrolling.
-     *
-     * @return The elapsed time in milliseconds.
-     */
-    public int timePassed() {
-        return (int)(AnimationUtils.currentAnimationTimeMillis() - mStartTime);
-    }
-
-    /**
-     * Sets the final position (X) for this scroller.
-     *
-     * @param newX The new X offset as an absolute distance from the origin.
-     * @see #extendDuration(int)
-     * @see #setFinalY(int)
-     */
-    public void setFinalX(int newX) {
-        mFinalX = newX;
-        mDeltaX = mFinalX - mStartX;
-        mFinished = false;
-    }
-
-    /**
-     * Sets the final position (Y) for this scroller.
-     *
-     * @param newY The new Y offset as an absolute distance from the origin.
-     * @see #extendDuration(int)
-     * @see #setFinalX(int)
-     */
-    public void setFinalY(int newY) {
-        mFinalY = newY;
-        mDeltaY = mFinalY - mStartY;
-        mFinished = false;
-    }
-
-    /**
-     * @hide
-     */
-    public boolean isScrollingInDirection(float xvel, float yvel) {
-        return !mFinished && Math.signum(xvel) == Math.signum(mFinalX - mStartX) &&
-                Math.signum(yvel) == Math.signum(mFinalY - mStartY);
     }
 }