From 4b66a8a8ad0897e48475d13e865285f210701bb7 Mon Sep 17 00:00:00 2001
From: Riddle Hsu <riddlehsu@google.com>
Date: Thu, 28 Apr 2022 22:53:00 +0800
Subject: [PATCH] Initialize transition layer of wallpaper at bottom

Otherwise the wallpaper may be shown above the app during
transition. The case may happen when performing seamless
display change transition with visible wallpaper.

Bug: 229701688
Test: atest com.android.server.wm.flicker.launch.OpenAppColdTest
Change-Id: Ib7b448caec6d1c1f1383b7e4229394437afd1b58
---
 .../wm/shell/transition/Transitions.java      | 24 ++++++++++++-------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
index e4c94264be2c6..273237846156a 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
@@ -309,13 +309,14 @@ public class Transitions implements RemoteCallable<Transitions> {
         if (info.getRootLeash().isValid()) {
             t.show(info.getRootLeash());
         }
+        final int numChanges = info.getChanges().size();
         // Put animating stuff above this line and put static stuff below it.
-        int zSplitLine = info.getChanges().size();
+        final int zSplitLine = numChanges + 1;
         // changes should be ordered top-to-bottom in z
-        for (int i = info.getChanges().size() - 1; i >= 0; --i) {
+        for (int i = numChanges - 1; i >= 0; --i) {
             final TransitionInfo.Change change = info.getChanges().get(i);
             final SurfaceControl leash = change.getLeash();
-            final int mode = info.getChanges().get(i).getMode();
+            final int mode = change.getMode();
 
             // Don't reparent anything that isn't independent within its parents
             if (!TransitionInfo.isIndependent(change, info)) {
@@ -329,26 +330,31 @@ public class Transitions implements RemoteCallable<Transitions> {
                 t.setPosition(leash, change.getStartAbsBounds().left - info.getRootOffset().x,
                         change.getStartAbsBounds().top - info.getRootOffset().y);
             }
+            final int layer;
             // Put all the OPEN/SHOW on top
-            if (mode == TRANSIT_OPEN || mode == TRANSIT_TO_FRONT) {
+            if ((change.getFlags() & FLAG_IS_WALLPAPER) != 0) {
+                // Wallpaper is always at the bottom.
+                layer = 0;
+            } else if (mode == TRANSIT_OPEN || mode == TRANSIT_TO_FRONT) {
                 if (isOpening) {
                     // put on top
-                    t.setLayer(leash, zSplitLine + info.getChanges().size() - i);
+                    layer = zSplitLine + numChanges - i;
                 } else {
                     // put on bottom
-                    t.setLayer(leash, zSplitLine - i);
+                    layer = zSplitLine - i;
                 }
             } else if (mode == TRANSIT_CLOSE || mode == TRANSIT_TO_BACK) {
                 if (isOpening) {
                     // put on bottom and leave visible
-                    t.setLayer(leash, zSplitLine - i);
+                    layer = zSplitLine - i;
                 } else {
                     // put on top
-                    t.setLayer(leash, zSplitLine + info.getChanges().size() - i);
+                    layer = zSplitLine + numChanges - i;
                 }
             } else { // CHANGE or other
-                t.setLayer(leash, zSplitLine + info.getChanges().size() - i);
+                layer = zSplitLine + numChanges - i;
             }
+            t.setLayer(leash, layer);
         }
     }