Add show wallpaper feature for back navigation

For the back gesture animation, we want to show the wallpaper but we
don't have any wallpaper targer, so we introduce a new flag to set the
focused window as wallpaper target if it have to show the wallpaper.

Test: Manual with the upcoming CL implementing the cross-task animation
Bug: 241808055
Change-Id: I97b27dc009fe0d017083d16f7117f04d93fb2beb

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

@@ -460,7 +460,7 @@ public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
     private final ClientLifecycleManager mLifecycleManager;
 
     @Nullable
-    private final BackNavigationController mBackNavigationController;
+    final BackNavigationController mBackNavigationController;
 
     private TaskChangeNotificationController mTaskChangeNotificationController;
     /** The controller for all operations related to locktask. */

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

@@ -57,6 +57,9 @@ class BackNavigationController {
     private static final String TAG = "BackNavigationController";
     private WindowManagerService mWindowManagerService;
     private IWindowFocusObserver mFocusObserver;
+    private boolean mBackAnimationInProgress;
+    private boolean mShowWallpaper;
+    private Runnable mPendingAnimation;
 
     /**
      * Returns true if the back predictability feature is enabled
@@ -208,6 +211,7 @@ class BackNavigationController {
                 return infoBuilder.setType(backType).build();
             }
 
+            mBackAnimationInProgress = true;
             // We don't have an application callback, let's find the destination of the back gesture
             Task finalTask = currentTask;
             prevActivity = currentTask.getActivity(
@@ -228,6 +232,7 @@ class BackNavigationController {
                 // Our Task should bring back to home
                 removedWindowContainer = currentTask;
                 backType = BackNavigationInfo.TYPE_RETURN_TO_HOME;
+                mShowWallpaper = true;
             } else if (currentActivity.isRootOfTask()) {
                 // TODO(208789724): Create single source of truth for this, maybe in
                 //  RootWindowContainer
@@ -240,6 +245,7 @@ class BackNavigationController {
                 } else {
                     backType = BackNavigationInfo.TYPE_CROSS_TASK;
                 }
+                mShowWallpaper = true;
             }
             infoBuilder.setType(backType);
 
@@ -369,6 +375,13 @@ class BackNavigationController {
             }
         }
 
+        if (mShowWallpaper) {
+            currentTask.getDisplayContent().mWallpaperController.adjustWallpaperWindows();
+            // TODO(b/241808055): If the current animation need to show wallpaper and animate the
+            //  wallpaper, start the wallpaper animation to collect wallpaper target and deliver it
+            //  to the back animation controller.
+        }
+
         final RemoteAnimationTarget[] targets = (behindAppTarget == null)
                 ? new RemoteAnimationTarget[] {topAppTarget}
                 : new RemoteAnimationTarget[] {topAppTarget, behindAppTarget};
@@ -399,7 +412,7 @@ class BackNavigationController {
                     }
                 };
 
-        startAnimation(backType, targets, adapter, callback);
+        scheduleAnimationLocked(backType, targets, adapter, callback);
     }
 
     @NonNull
@@ -445,17 +458,38 @@ class BackNavigationController {
     }
 
     @VisibleForTesting
-    void startAnimation(@BackNavigationInfo.BackTargetType int type,
+    void scheduleAnimationLocked(@BackNavigationInfo.BackTargetType int type,
             RemoteAnimationTarget[] targets, BackAnimationAdapter backAnimationAdapter,
             IBackAnimationFinishedCallback callback) {
-        mWindowManagerService.mAnimator.addAfterPrepareSurfacesRunnable(() -> {
+        mPendingAnimation = () -> {
             try {
                 backAnimationAdapter.getRunner().onAnimationStart(type,
                         targets, null, null, callback);
             } catch (RemoteException e) {
                 e.printStackTrace();
             }
-        });
+        };
+        mWindowManagerService.mWindowPlacerLocked.requestTraversal();
+    }
+
+    void checkAnimationReady(WallpaperController wallpaperController) {
+        if (!mBackAnimationInProgress) {
+            return;
+        }
+
+        final boolean wallpaperReady = !mShowWallpaper
+                || (wallpaperController.getWallpaperTarget() != null
+                && wallpaperController.wallpaperTransitionReady());
+        if (wallpaperReady && mPendingAnimation != null) {
+            startAnimation();
+        }
+    }
+
+    void startAnimation() {
+        if (mPendingAnimation != null) {
+            mPendingAnimation.run();
+            mPendingAnimation = null;
+        }
     }
 
     private void onBackNavigationDone(Bundle result, WindowState focusedWindow, int backType) {
@@ -468,6 +502,8 @@ class BackNavigationController {
             focusedWindow.unregisterFocusObserver(mFocusObserver);
             mFocusObserver = null;
         }
+        mBackAnimationInProgress = false;
+        mShowWallpaper = false;
     }
 
     private HardwareBuffer getActivitySnapshot(@NonNull Task task,
@@ -544,4 +580,11 @@ class BackNavigationController {
                 "Setting Activity.mLauncherTaskBehind to false. Activity=%s",
                 activity);
     }
+
+    boolean isWallpaperVisible(WindowState w) {
+        if (mBackAnimationInProgress && w.isFocused()) {
+            return mShowWallpaper;
+        }
+        return false;
+    }
 }

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

@@ -837,6 +837,11 @@ class RootWindowContainer extends WindowContainer<DisplayContent>
         if (recentsAnimationController != null) {
             recentsAnimationController.checkAnimationReady(defaultDisplay.mWallpaperController);
         }
+        final BackNavigationController backNavigationController =
+                mWmService.mAtmService.mBackNavigationController;
+        if (backNavigationController != null) {
+            backNavigationController.checkAnimationReady(defaultDisplay.mWallpaperController);
+        }
 
         for (int displayNdx = 0; displayNdx < mChildren.size(); ++displayNdx) {
             final DisplayContent displayContent = mChildren.get(displayNdx);

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

@@ -197,7 +197,7 @@ class WallpaperController {
                 && animatingContainer.getAnimation() != null
                 && animatingContainer.getAnimation().getShowWallpaper();
         final boolean hasWallpaper = w.hasWallpaper() || animationWallpaper;
-        if (isRecentsTransitionTarget(w)) {
+        if (isRecentsTransitionTarget(w) || isBackNavigationTarget(w)) {
             if (DEBUG_WALLPAPER) Slog.v(TAG, "Found recents animation wallpaper target: " + w);
             mFindResults.setWallpaperTarget(w);
             return true;
@@ -237,6 +237,12 @@ class WallpaperController {
         return controller != null && controller.isWallpaperVisible(w);
     }
 
+    private boolean isBackNavigationTarget(WindowState w) {
+        // The window is in animating by back navigation and set to show wallpaper.
+        final BackNavigationController controller = mService.mAtmService.mBackNavigationController;
+        return controller != null && controller.isWallpaperVisible(w);
+    }
+
     /**
      * @see #computeLastWallpaperZoomOut()
      */
@@ -822,6 +828,12 @@ class WallpaperController {
             if (mService.getRecentsAnimationController() != null) {
                 mService.getRecentsAnimationController().startAnimation();
             }
+
+            // If there was a pending back navigation animation that would show wallpaper, start
+            // the animation due to it was skipped in previous surface placement.
+            if (mService.mAtmService.mBackNavigationController != null) {
+                mService.mAtmService.mBackNavigationController.startAnimation();
+            }
             return true;
         }
         return false;

services/tests/wmtests/src/com/android/server/wm/BackNavigationControllerTests.java

@@ -90,7 +90,7 @@ public class BackNavigationControllerTests extends WindowTestsBase {
                 .isEqualTo(typeToString(BackNavigationInfo.TYPE_RETURN_TO_HOME));
 
         // verify if back animation would start.
-        verify(mBackNavigationController).startAnimation(
+        verify(mBackNavigationController).scheduleAnimationLocked(
                 eq(BackNavigationInfo.TYPE_RETURN_TO_HOME), any(), eq(mBackAnimationAdapter),
                 any());
     }