Reland: Clear transitions for app windows display change.

This prevents unwanted animations from running for windows on the new
display that are no longer relevant.
Also,
- Transfer the opening app token transition to the new display so that
it can be eventually made visible on that display
- Clean-up TODO relating to moving VR activity to main display, so that
the right states are set.

Bug: 128449959
Test: VrDisplayTests
Test: manual - launch activity with options moving between virtual and
default display, atest WmTests

Change-Id: I285c6742839d38e76322621b9c2a1d7f313cd6f8

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

@@ -4781,18 +4781,12 @@ public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
 
     private void applyUpdateVrModeLocked(ActivityRecord r) {
         // VR apps are expected to run in a main display. If an app is turning on VR for
-        // itself, but lives in a dynamic stack, then make sure that it is moved to the main
-        // fullscreen stack before enabling VR Mode.
-        // TODO: The goal of this code is to keep the VR app on the main display. When the
-        // stack implementation changes in the future, keep in mind that the use of the fullscreen
-        // stack is a means to move the activity to the main display and a moveActivityToDisplay()
-        // option would be a better choice here.
+        // itself, but isn't on the main display, then move it there before enabling VR Mode.
         if (r.requestedVrComponent != null && r.getDisplayId() != DEFAULT_DISPLAY) {
-            Slog.i(TAG, "Moving " + r.shortComponentName + " from stack " + r.getStackId()
-                    + " to main stack for VR");
-            final ActivityStack stack = mRootActivityContainer.getDefaultDisplay().getOrCreateStack(
-                    WINDOWING_MODE_FULLSCREEN, r.getActivityType(), true /* toTop */);
-            moveTaskToStack(r.getTaskRecord().taskId, stack.mStackId, true /* toTop */);
+            Slog.i(TAG, "Moving " + r.shortComponentName + " from display " + r.getDisplayId()
+                    + " to main display for VR");
+            mRootActivityContainer.moveStackToDisplay(
+                    r.getStackId(), DEFAULT_DISPLAY, true /* toTop */);
         }
         mH.post(() -> {
             if (!mVrController.onVrModeChanged(r)) {

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

@@ -1322,7 +1322,15 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
         if (prevDc == null || prevDc == mDisplayContent) {
             return;
         }
-        if (prevDc.mChangingApps.contains(this)) {
+
+        if (prevDc.mOpeningApps.remove(this)) {
+            // Transfer opening transition to new display.
+            mDisplayContent.mOpeningApps.add(this);
+            mDisplayContent.prepareAppTransition(prevDc.mAppTransition.getAppTransition(), true);
+            mDisplayContent.executeAppTransition();
+        }
+
+        if (prevDc.mChangingApps.remove(this)) {
             // This gets called *after* the AppWindowToken has been reparented to the new display.
             // That reparenting resulted in this window changing modes (eg. FREEFORM -> FULLSCREEN),
             // so this token is now "frozen" while waiting for the animation to start on prevDc
@@ -1331,6 +1339,8 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
             // so we need to cancel the change transition here.
             clearChangeLeash(getPendingTransaction(), true /* cancel */);
         }
+        prevDc.mClosingApps.remove(this);
+
         if (prevDc.mFocusedApp == this) {
             prevDc.setFocusedApp(null);
             final TaskStack stack = dc.getTopStack();
@@ -3216,16 +3226,6 @@ class AppWindowToken extends WindowToken implements WindowManagerService.AppFree
                 true /* topToBottom */);
     }
 
-    void removeFromPendingTransition() {
-        if (isWaitingForTransitionStart() && mDisplayContent != null) {
-            mDisplayContent.mOpeningApps.remove(this);
-            if (mDisplayContent.mChangingApps.remove(this)) {
-                clearChangeLeash(getPendingTransaction(), true /* cancel */);
-            }
-            mDisplayContent.mClosingApps.remove(this);
-        }
-    }
-
     private void updateColorTransform() {
         if (mSurfaceControl != null && mLastAppSaturationInfo != null) {
             getPendingTransaction().setColorTransform(mSurfaceControl,

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

@@ -2398,9 +2398,6 @@ class DisplayContent extends WindowContainer<DisplayContent.DisplayChildWindowCo
                     + " to its current displayId=" + mDisplayId);
         }
 
-        // Clean up all pending transitions when stack reparent to another display.
-        stack.forAllAppWindows(AppWindowToken::removeFromPendingTransition);
-
         prevDc.mTaskStackContainers.removeChild(stack);
         mTaskStackContainers.addStackToDisplay(stack, onTop);
     }