Fix PIP snapping to incorrect location.

animateToClosestSnapTarget is no longer used, we always use flingToSnapTarget now. If velocity is low/zero, the fling animation will end and a spring animation will spring it to the nearest allowable location.

This also incorporates a fix to PhysicsAnimator (cl/296316037) to more accurately decide if a fling is strong enough to reach the other side of the screen. This fixes an issue where pushing PIP off-screen and then very gently moving it back on screen caused it to jump to the other side of the screen.

Fixes: 154937295
Test: manual
Change-Id: I6f0284195bcb802f4cdd58cc06457023dcf63aa1

packages/SystemUI/src/com/android/systemui/pip/phone/PipMotionHelper.java

@@ -327,15 +327,6 @@ public class PipMotionHelper implements PipAppOpsListener.Callback,
         startBoundsAnimator(xEndValue /* toX */, estimatedFlingYEndValue /* toY */);
     }
 
-    /**
-     * Animates the PiP to the closest snap target.
-     */
-    void animateToClosestSnapTarget() {
-        final Rect newBounds = new Rect();
-        mSnapAlgorithm.snapRectToClosestEdge(mBounds, mMovementBounds, newBounds);
-        animateToBounds(newBounds, mSpringConfig);
-    }
-
     /**
      * Animates PIP to the provided bounds, using physics animations and the given spring
      * configuration

packages/SystemUI/src/com/android/systemui/pip/phone/PipTouchHandler.java

@@ -885,7 +885,6 @@ public class PipTouchHandler {
 
             final PointF vel = touchState.getVelocity();
             final float velocity = PointF.length(vel.x, vel.y);
-            final boolean isFling = velocity > mFlingAnimationUtils.getMinVelocityPxPerSecond();
 
             if (touchState.isDragging()) {
                 Runnable endAction = null;
@@ -900,13 +899,9 @@ public class PipTouchHandler {
                     endAction = mMenuController::hideMenu;
                 }
 
-                if (isFling) {
-                    mMotionHelper.flingToSnapTarget(vel.x, vel.y,
-                            PipTouchHandler.this::updateDismissFraction /* updateAction */,
-                            endAction /* endAction */);
-                } else {
-                    mMotionHelper.animateToClosestSnapTarget();
-                }
+                mMotionHelper.flingToSnapTarget(vel.x, vel.y,
+                        PipTouchHandler.this::updateDismissFraction /* updateAction */,
+                        endAction /* endAction */);
             } else if (mTouchState.isDoubleTap()) {
                 // Expand to fullscreen if this is a double tap
                 // the PiP should be frozen until the transition ends

packages/SystemUI/src/com/android/systemui/util/animation/PhysicsAnimator.kt

@@ -311,10 +311,25 @@ class PhysicsAnimator<T> private constructor (val target: T) {
         val springConfigCopy = springConfig.copy()
         val toAtLeast = if (startVelocity < 0) flingConfig.min else flingConfig.max
 
-        // If the fling needs to reach min/max, calculate the velocity required to do so and use
-        // that if the provided start velocity is not sufficient.
-        if (flingMustReachMinOrMax &&
-                toAtLeast != -Float.MAX_VALUE && toAtLeast != Float.MAX_VALUE) {
+        if (flingMustReachMinOrMax && isValidValue(toAtLeast)) {
+            val currentValue = property.getValue(target)
+            val flingTravelDistance =
+                    startVelocity / (flingConfig.friction * FLING_FRICTION_SCALAR_MULTIPLIER)
+            val projectedFlingEndValue = currentValue + flingTravelDistance
+            val midpoint = (flingConfig.min + flingConfig.max) / 2
+
+            // If fling velocity is too low to push the target past the midpoint between min and
+            // max, then spring back towards the nearest edge, starting with the current velocity.
+            if ((startVelocity < 0 && projectedFlingEndValue > midpoint) ||
+                    (startVelocity > 0 && projectedFlingEndValue < midpoint)) {
+                val toPosition =
+                        if (projectedFlingEndValue < midpoint) flingConfig.min else flingConfig.max
+                if (isValidValue(toPosition)) {
+                    return spring(property, toPosition, startVelocity, springConfig)
+                }
+            }
+
+            // Projected fling end value is past the midpoint, so fling forward.
             val distanceToDestination = toAtLeast - property.getValue(target)
 
             // The minimum velocity required for the fling to end up at the given destination,
@@ -345,6 +360,8 @@ class PhysicsAnimator<T> private constructor (val target: T) {
         return this
     }
 
+    private fun isValidValue(value: Float) = value < Float.MAX_VALUE && value > -Float.MAX_VALUE
+
     /**
      * Adds a listener that will be called whenever any property on the animated object is updated.
      * This will be called on every animation frame, with the current value of the animated object