From 57dab6fa29d28c0ff6ebdb2ee5b31b0a098ec332 Mon Sep 17 00:00:00 2001
From: Jon Miranda <jonmiranda@google.com>
Date: Fri, 10 Apr 2020 13:38:14 -0700
Subject: [PATCH] Let spring take over the overscroll amount when swiping to
 first/last page.

Bug: 153747836
Change-Id: I8a883f648587b0cb4008df3b8176c9341162b8d1
---
 res/values/config.xml                          |  4 ++--
 src/com/android/launcher3/PagedView.java       | 18 +++++++++++++++---
 .../android/launcher3/util/OverScroller.java   |  9 +++++----
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/res/values/config.xml b/res/values/config.xml
index ef6761387c..0657b86a6c 100644
--- a/res/values/config.xml
+++ b/res/values/config.xml
@@ -131,8 +131,8 @@
     <item name="dismiss_task_trans_x_damping_ratio" type="dimen" format="float">0.5</item>
     <item name="dismiss_task_trans_x_stiffness" type="dimen" format="float">1500</item>
 
-    <item name="horizontal_spring_damping_ratio" type="dimen" format="float">0.75</item>
-    <item name="horizontal_spring_stiffness" type="dimen" format="float">200</item>
+    <item name="horizontal_spring_damping_ratio" type="dimen" format="float">0.8</item>
+    <item name="horizontal_spring_stiffness" type="dimen" format="float">400</item>
 
     <item name="swipe_up_rect_scale_damping_ratio" type="dimen" format="float">0.75</item>
     <item name="swipe_up_rect_scale_stiffness" type="dimen" format="float">200</item>
diff --git a/src/com/android/launcher3/PagedView.java b/src/com/android/launcher3/PagedView.java
index 7474613a18..5343424dfc 100644
--- a/src/com/android/launcher3/PagedView.java
+++ b/src/com/android/launcher3/PagedView.java
@@ -1069,16 +1069,28 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
         }
     }
 
+    /**
+     * Returns the amount of overscroll caused by the spring in {@link OverScroller}.
+     */
+    private int getSpringOverScroll(int amount) {
+        if (mScroller.isSpringing()) {
+            return amount < 0
+                    ? mScroller.getCurrPos()
+                    : Math.max(0, mScroller.getCurrPos() - mMaxScroll);
+        } else {
+            return 0;
+        }
+    }
+
     protected void dampedOverScroll(int amount) {
-        mSpringOverScroll = amount;
         if (amount == 0) {
             return;
         }
 
         int size = mOrientationHandler.getMeasuredSize(this);
         int overScrollAmount = OverScroll.dampedScroll(amount, size);
-        mSpringOverScroll = overScrollAmount;
         if (mScroller.isSpringing()) {
+            mSpringOverScroll = getSpringOverScroll(amount);
             invalidate();
             return;
         }
@@ -1090,8 +1102,8 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
     }
 
     protected void overScroll(int amount) {
-        mSpringOverScroll = amount;
         if (mScroller.isSpringing()) {
+            mSpringOverScroll = getSpringOverScroll(amount);
             invalidate();
             return;
         }
diff --git a/src/com/android/launcher3/util/OverScroller.java b/src/com/android/launcher3/util/OverScroller.java
index 34efb12e01..87e698626d 100644
--- a/src/com/android/launcher3/util/OverScroller.java
+++ b/src/com/android/launcher3/util/OverScroller.java
@@ -561,10 +561,11 @@ public class OverScroller {
             mStartTime = AnimationUtils.currentAnimationTimeMillis();
             mDuration = duration;
 
+            if (mSpring != null) {
+                mSpring.cancel();
+            }
+
             if (mState == SPRING) {
-                if (mSpring != null) {
-                    mSpring.cancel();
-                }
                 mSpring = new SpringAnimation(this, SPRING_PROPERTY);
 
                 ResourceProvider rp = DynamicResource.provider(mContext);
@@ -576,9 +577,9 @@ public class OverScroller {
                 mSpring.setStartVelocity(velocity);
                 mSpring.animateToFinalPosition(mFinal);
                 mSpring.addEndListener((animation, canceled, value, velocity1) -> {
+                    mSpring = null;
                     finish();
                     mState = SPLINE;
-                    mSpring = null;
                 });
             }
             // Unused