From 575ffb856ec7a91701a79840cad315102eaa0afd Mon Sep 17 00:00:00 2001
From: George Mount <mount@google.com>
Date: Wed, 7 Feb 2018 12:38:47 -0800
Subject: [PATCH] Fix bug in calculating path in ArcMotion

Bug: 73077523

When the path is perfectly horizontal, ArcMotion
was calculating a Path that had NaN values. This
corrects that problem by special casing horizontal
and vertical paths.

Test: manual with app that discovered the problem
Test: manual with test app
Test: I30d51206194e3c68ea145d3a81e05a461c4e0ca8
Change-Id: Ic1a70b79290847726fc7994d1224fd77024e0610
---
 core/java/android/transition/ArcMotion.java | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/core/java/android/transition/ArcMotion.java b/core/java/android/transition/ArcMotion.java
index da1483499220f..172c8376c8cca 100644
--- a/core/java/android/transition/ArcMotion.java
+++ b/core/java/android/transition/ArcMotion.java
@@ -216,7 +216,13 @@ public class ArcMotion extends PathMotion {
 
         boolean isMovingUpwards = startY > endY;
 
-        if ((Math.abs(deltaX) < Math.abs(deltaY))) {
+        if (deltaY == 0) {
+            ex = dx;
+            ey = dy + (Math.abs(deltaX) * 0.5f * mMinimumHorizontalTangent);
+        } else if (deltaX == 0) {
+            ex = dx + (Math.abs(deltaY) * 0.5f * mMinimumVerticalTangent);
+            ey = dy;
+        } else if ((Math.abs(deltaX) < Math.abs(deltaY))) {
             // Similar triangles bfa and bde mean that (ab/fb = eb/bd)
             // Therefore, eb = ab * bd / fb
             // ab = hypotenuse
@@ -254,7 +260,7 @@ public class ArcMotion extends PathMotion {
         float maximumArcDist2 = midDist2 * mMaximumTangent * mMaximumTangent;
 
         float newArcDistance2 = 0;
-        if (arcDist2 < minimumArcDist2) {
+        if (arcDist2 != 0 && arcDist2 < minimumArcDist2) {
             newArcDistance2 = minimumArcDist2;
         } else if (arcDist2 > maximumArcDist2) {
             newArcDistance2 = maximumArcDist2;