From f059091fc6ec78e82d84d4e5f874cbf495717531 Mon Sep 17 00:00:00 2001
From: Miranda Kephart <mkephart@google.com>
Date: Fri, 21 May 2021 20:48:47 +0000
Subject: [PATCH] Update screenshot dismiss gesture physics

Allow fling and make dismiss velocity dependent upon fling velocity.
Also run return animation instead of dismiss animation if drag
direction reverses, even if the absolute distance travelled is still
higher than the threshold.

Bug: 188904645
Test: manual
Change-Id: I871948ac0267039eac7e7f723544cf2a64fc1120
---
 .../systemui/screenshot/ScreenshotView.java   | 40 +++++++++++++++++--
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/packages/SystemUI/src/com/android/systemui/screenshot/ScreenshotView.java b/packages/SystemUI/src/com/android/systemui/screenshot/ScreenshotView.java
index af4836d997fa1..facebee52943f 100644
--- a/packages/SystemUI/src/com/android/systemui/screenshot/ScreenshotView.java
+++ b/packages/SystemUI/src/com/android/systemui/screenshot/ScreenshotView.java
@@ -861,11 +861,15 @@ public class ScreenshotView extends FrameLayout implements
 
     class SwipeDismissHandler implements OnTouchListener {
         // distance needed to register a dismissal
-        private static final float DISMISS_DISTANCE_THRESHOLD_DP = 30;
+        private static final float DISMISS_DISTANCE_THRESHOLD_DP = 20;
 
         private final GestureDetector mGestureDetector;
 
         private float mStartX;
+        // Keeps track of the most recent direction (between the last two move events).
+        // -1 for left; +1 for right.
+        private int mDirectionX;
+        private float mPreviousX;
 
         SwipeDismissHandler() {
             GestureDetector.OnGestureListener gestureListener = new SwipeDismissGestureListener();
@@ -878,6 +882,7 @@ public class ScreenshotView extends FrameLayout implements
             mCallbacks.onUserInteraction();
             if (event.getActionMasked() == MotionEvent.ACTION_DOWN) {
                 mStartX = event.getRawX();
+                mPreviousX = mStartX;
                 return true;
             } else if (event.getActionMasked() == MotionEvent.ACTION_UP) {
                 if (isPastDismissThreshold()
@@ -906,16 +911,42 @@ public class ScreenshotView extends FrameLayout implements
             public boolean onScroll(
                     MotionEvent ev1, MotionEvent ev2, float distanceX, float distanceY) {
                 mScreenshotStatic.setTranslationX(ev2.getRawX() - mStartX);
+                mDirectionX = (ev2.getRawX() < mPreviousX) ? -1 : 1;
+                mPreviousX = ev2.getRawX();
                 return true;
             }
+
+            @Override
+            public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
+                    float velocityY) {
+                if (mScreenshotStatic.getTranslationX() * velocityX > 0
+                        && (mDismissAnimation == null || !mDismissAnimation.isRunning())) {
+                    animateDismissal(createSwipeDismissAnimation(velocityX / (float) 1000));
+                    return true;
+                }
+                return false;
+            }
         }
 
         private boolean isPastDismissThreshold() {
-            float distance = Math.abs(mScreenshotStatic.getTranslationX());
-            return distance >= dpToPx(DISMISS_DISTANCE_THRESHOLD_DP);
+            float translationX = mScreenshotStatic.getTranslationX();
+            // Determines whether the absolute translation from the start is in the same direction
+            // as the current movement. For example, if the user moves most of the way to the right,
+            // but then starts dragging back left, we do not dismiss even though the absolute
+            // distance is greater than the threshold.
+            if (translationX * mDirectionX > 0) {
+                return Math.abs(translationX) >= dpToPx(DISMISS_DISTANCE_THRESHOLD_DP);
+            }
+            return false;
         }
 
         private ValueAnimator createSwipeDismissAnimation() {
+            return createSwipeDismissAnimation(1);
+        }
+
+        private ValueAnimator createSwipeDismissAnimation(float velocity) {
+            // velocity is measured in pixels per millisecond
+            velocity = Math.min(3, Math.max(1, velocity));
             ValueAnimator anim = ValueAnimator.ofFloat(0, 1);
             float startX = mScreenshotStatic.getTranslationX();
             // make sure the UI gets all the way off the screen in the direction of movement
@@ -924,13 +955,14 @@ public class ScreenshotView extends FrameLayout implements
             float finalX = startX < 0
                     ? -1 * mActionsContainerBackground.getRight()
                     : mDisplayMetrics.widthPixels;
+            float distance = Math.abs(finalX - startX);
 
             anim.addUpdateListener(animation -> {
                 float translation = MathUtils.lerp(startX, finalX, animation.getAnimatedFraction());
                 mScreenshotStatic.setTranslationX(translation);
                 setAlpha(1 - animation.getAnimatedFraction());
             });
-            anim.setDuration(400);
+            anim.setDuration((long) (distance / Math.abs(velocity)));
             return anim;
         }