Merge "Allow WindowState to assign layer during transition." into udc-dev

services/core/java/com/android/server/wm/TransitionController.java

@@ -516,8 +516,14 @@ class TransitionController {
      * playing, but can be "opened-up" for certain transition operations like calculating layers
      * for finishTransaction.
      */
-    boolean canAssignLayers() {
-        return mBuildingFinishLayers || !isPlaying();
+    boolean canAssignLayers(@NonNull WindowContainer wc) {
+        // Don't build window state into finish transaction in case another window is added or
+        // removed during transition playing.
+        if (mBuildingFinishLayers) {
+            return wc.asWindowState() == null;
+        }
+        // Always allow WindowState to assign layers since it won't affect transition.
+        return wc.asWindowState() != null || !isPlaying();
     }
 
     @WindowConfiguration.WindowingMode

services/core/java/com/android/server/wm/WindowContainer.java

@@ -2596,7 +2596,7 @@ class WindowContainer<E extends WindowContainer> extends ConfigurationContainer<
     void assignLayer(Transaction t, int layer) {
         // Don't assign layers while a transition animation is playing
         // TODO(b/173528115): establish robust best-practices around z-order fighting.
-        if (!mTransitionController.canAssignLayers()) return;
+        if (!mTransitionController.canAssignLayers(this)) return;
         final boolean changed = layer != mLastLayer || mLastRelativeToLayer != null;
         if (mSurfaceControl != null && changed) {
             setLayer(t, layer);