From ffad14c9638381fb8611c0657bdfd7882acda5cf Mon Sep 17 00:00:00 2001
From: Johannes Gallmann <gallmann@google.com>
Date: Wed, 12 Mar 2025 15:12:49 +0000
Subject: Fix BackAnimationController race condition

This CL fixes a race condition in BackAnimationController. Since
onThresholdCrossed is not executed on the shell main thread, the
ordering between other BackAnimation API function calls was not
guaranteed. Namely, onThresholdCrossed could have been executed before
the first MOVE event was processed, resulting in  startBackAnimation not
being called. In that case, BackAnimationController injected legacy back
events as a fallback instead of playing the predictive back animation.
Executing onThresholdCrossed on the shell main thread instead should
resolve this problem.

Additionally, the recently implemented small related change (commit 13423234d99327cf16fec9ac76b8bd116a586b26) in EBGH is
put behind the predictiveBackDelayWmTransition flag as well.

Bug: 401832380
Flag: com.android.systemui.predictive_back_delay_wm_transition
Test: BackGestureInvokedTest
Change-Id: I77d0d1de66934754cc64330130d4bd34b4634796
---
 .../src/com/android/wm/shell/back/BackAnimationController.java      | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'libs')

diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
index 53dede6bd227..5d59af940da0 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
@@ -332,7 +332,11 @@ public class BackAnimationController implements RemoteCallable<BackAnimationCont
 
         @Override
         public void onThresholdCrossed() {
-            BackAnimationController.this.onThresholdCrossed();
+            if (predictiveBackDelayWmTransition()) {
+                mShellExecutor.execute(BackAnimationController.this::onThresholdCrossed);
+            } else {
+                BackAnimationController.this.onThresholdCrossed();
+            }
         }
 
         @Override
-- 
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