From 7b3d11dce3a4039a8726b0a91a4069a79dd30f08 Mon Sep 17 00:00:00 2001
From: Robert Carr <racarr@google.com>
Date: Thu, 15 Mar 2018 14:34:45 -0700
Subject: [PATCH] Ensure Surface is recreated if children are detached.

If we detach the children of a Surface, then they are stuck
around indefinitely and we can't use the Surface as the result
of a future call to lay-out visible. This should also improve
Surface lifetime-errors as now in the case of cancelling
an exit animation we will fall in to this preserve surface
codepath instead of the destroySurfaceUnchecked block in
WindowStateAnimator#cancelExitAnimationForNextAnimationLocked.

Bug: 68996752
Bug: 62536731
Bug: 72921025
Bug: 72873272
Change-Id: Ib0be6e7447c04d00bff8784d8b8072918d48e0ba
---
 .../core/java/com/android/server/wm/WindowState.java     | 9 +++++++++
 .../java/com/android/server/wm/WindowStateAnimator.java  | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/services/core/java/com/android/server/wm/WindowState.java b/services/core/java/com/android/server/wm/WindowState.java
index 68bb530fdf256..97d00bea27f20 100644
--- a/services/core/java/com/android/server/wm/WindowState.java
+++ b/services/core/java/com/android/server/wm/WindowState.java
@@ -4297,6 +4297,15 @@ class WindowState extends WindowContainer<WindowState> implements WindowManagerP
         final boolean wasVisible = isVisibleLw();
 
         result |= (!wasVisible || !isDrawnLw()) ? RELAYOUT_RES_FIRST_TIME : 0;
+
+        if (mWinAnimator.mChildrenDetached) {
+            // If there are detached children hanging around we need to force
+            // the client receiving a new Surface.
+            mWinAnimator.preserveSurfaceLocked();
+            result |= RELAYOUT_RES_SURFACE_CHANGED
+                    | RELAYOUT_RES_FIRST_TIME;
+        }
+
         if (mAnimatingExit) {
             Slog.d(TAG, "relayoutVisibleWindow: " + this + " mAnimatingExit=true, mRemoveOnExit="
                     + mRemoveOnExit + ", mDestroying=" + mDestroying);
diff --git a/services/core/java/com/android/server/wm/WindowStateAnimator.java b/services/core/java/com/android/server/wm/WindowStateAnimator.java
index 13f05e088cb1e..29beb58b334e6 100644
--- a/services/core/java/com/android/server/wm/WindowStateAnimator.java
+++ b/services/core/java/com/android/server/wm/WindowStateAnimator.java
@@ -221,6 +221,10 @@ class WindowStateAnimator {
 
     private final SurfaceControl.Transaction mReparentTransaction = new SurfaceControl.Transaction();
 
+    // Used to track whether we have called detach children on the way to invisibility, in which
+    // case we need to give the client a new Surface if it lays back out to a visible state.
+    boolean mChildrenDetached = false;
+
     WindowStateAnimator(final WindowState win) {
         final WindowManagerService service = win.mService;
 
@@ -430,6 +434,7 @@ class WindowStateAnimator {
         if (mSurfaceController != null) {
             return mSurfaceController;
         }
+        mChildrenDetached = false;
 
         if ((mWin.mAttrs.privateFlags & PRIVATE_FLAG_IS_ROUNDED_CORNERS_OVERLAY) != 0) {
             windowType = SurfaceControl.WINDOW_TYPE_DONT_SCREENSHOT;
@@ -1479,6 +1484,7 @@ class WindowStateAnimator {
         if (mSurfaceController != null) {
             mSurfaceController.detachChildren();
         }
+        mChildrenDetached = true;
     }
 
     int getLayer() {