Do not update task layer during collecting.

Which can prevents task layer be updated by pending transaction, no
matter that task has participant the transition. So the layer change
can always align with shell transition.
Then when transition ready, update the layers to start and finish
transaction, and correct the layer of transition roots after all layers
are assigned, so the last layer would be correct even if the reference
root window wasn't allow to assign layer by any reason.

Bug: 291510956
Test: tried on sample app, verify no flickering when close the task
with finishIfPossible or startActivityFromResult.

Change-Id: I4ccaca494780a636bd65f695bc9c9d9af9c7e5a4

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

@@ -959,20 +959,25 @@ class Transition implements BLASTSyncEngine.TransactionReadyListener {
         }
         // Need to update layers on involved displays since they were all paused while
         // the animation played. This puts the layers back into the correct order.
-        mController.mBuildingFinishLayers = true;
-        try {
-            for (int i = displays.size() - 1; i >= 0; --i) {
-                if (displays.valueAt(i) == null) continue;
-                displays.valueAt(i).assignChildLayers(t);
-            }
-        } finally {
-            mController.mBuildingFinishLayers = false;
+        for (int i = displays.size() - 1; i >= 0; --i) {
+            if (displays.valueAt(i) == null) continue;
+            updateDisplayLayers(displays.valueAt(i), t);
         }
+
         for (int i = 0; i < info.getRootCount(); ++i) {
             t.reparent(info.getRoot(i).getLeash(), null);
         }
     }
 
+    private static void updateDisplayLayers(DisplayContent dc, SurfaceControl.Transaction t) {
+        dc.mTransitionController.mBuildingFinishLayers = true;
+        try {
+            dc.assignChildLayers(t);
+        } finally {
+            dc.mTransitionController.mBuildingFinishLayers = false;
+        }
+    }
+
     /**
      * Build a transaction that cleans-up transition-only surfaces (transition root and snapshots).
      * This will ALWAYS be applied on transition finish just in-case
@@ -2346,8 +2351,9 @@ class Transition implements BLASTSyncEngine.TransactionReadyListener {
             final WindowContainer<?> wc = sortedTargets.get(i).mContainer;
             // Don't include wallpapers since they are in a different DA.
             if (isWallpaper(wc)) continue;
-            final int endDisplayId = getDisplayId(wc);
-            if (endDisplayId < 0) continue;
+            final DisplayContent dc = wc.getDisplayContent();
+            if (dc == null) continue;
+            final int endDisplayId = dc.getDisplayId();
 
             // Check if Root was already created for this display with a higher-Z window
             if (outInfo.findRootIndex(endDisplayId) >= 0) continue;
@@ -2369,6 +2375,9 @@ class Transition implements BLASTSyncEngine.TransactionReadyListener {
             final SurfaceControl rootLeash = leashReference.makeAnimationLeash().setName(
                     "Transition Root: " + leashReference.getName()).build();
             rootLeash.setUnreleasedWarningCallSite("Transition.calculateTransitionRoots");
+            // Update layers to start transaction because we prevent assignment during collect, so
+            // the layer of transition root can be correct.
+            updateDisplayLayers(dc, startT);
             startT.setLayer(rootLeash, leashReference.getLastLayer());
             outInfo.addRootLeash(endDisplayId, rootLeash,
                     ancestor.getBounds().left, ancestor.getBounds().top);

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

@@ -558,7 +558,9 @@ class TransitionController {
             return wc.asWindowState() == null;
         }
         // Always allow WindowState to assign layers since it won't affect transition.
-        return wc.asWindowState() != null || !isPlaying();
+        return wc.asWindowState() != null || (!isPlaying()
+                // Don't assign task while collecting.
+                && !(wc.asTask() != null && isCollecting()));
     }
 
     @WindowConfiguration.WindowingMode