Re-show faded PiP when fixed rotation is finished

PiP will be faded out if there is orientation change when
switching app (onFixedRotationStarted), and then fade in with
display transition from startAnimation -> fadeExistingPip.

But if there is no app switch, such as entering recent and
then return to current app, the signal to re-show the PiP was
missed in shell transition. So still listen to
onFixedRotationFinished and restore the visibility of PiP
when the transition is idle.

Bug: 262835608
Test: Enter PiP in portrait. Launch a rotatable app.
      Rotate screen to landscape.
      Either:
       - Swipe up and down to cancel.
       - Swipe up to enter recent.
         Click the current app to return.
      Though the PiP will be fade out during swipe-up gesture.
      After return to current app, the PiP should be still visible.

Change-Id: Ieb47eceaa5e8e7ff710a0fd6ab8319d1a3463985

libs/WindowManager/Shell/src/com/android/wm/shell/pip/PipTaskOrganizer.java

@@ -1002,6 +1002,7 @@ public class PipTaskOrganizer implements ShellTaskOrganizer.TaskListener,
             return;
         }
         if (Transitions.ENABLE_SHELL_TRANSITIONS) {
+            mPipTransitionController.onFixedRotationFinished();
             clearWaitForFixedRotation();
             return;
         }

libs/WindowManager/Shell/src/com/android/wm/shell/pip/PipTransition.java

@@ -412,9 +412,31 @@ public class PipTransition extends PipTransitionController {
 
     @Override
     public void onFixedRotationStarted() {
+        fadeEnteredPipIfNeed(false /* show */);
+    }
+
+    @Override
+    public void onFixedRotationFinished() {
+        fadeEnteredPipIfNeed(true /* show */);
+    }
+
+    private void fadeEnteredPipIfNeed(boolean show) {
         // The transition with this fixed rotation may be handled by other handler before reaching
         // PipTransition, so we cannot do this in #startAnimation.
-        if (mPipTransitionState.getTransitionState() == ENTERED_PIP && !mHasFadeOut) {
+        if (!mPipTransitionState.hasEnteredPip()) {
+            return;
+        }
+        if (show && mHasFadeOut) {
+            // If there is a pending transition, then let startAnimation handle it. And if it is
+            // handled, mHasFadeOut will be set to false and this runnable will be no-op. Otherwise
+            // make sure the PiP will reshow, e.g. swipe-up with fixed rotation (fade-out) but
+            // return to the current app (only finish the recent transition).
+            mTransitions.runOnIdle(() -> {
+                if (mHasFadeOut && mPipTransitionState.hasEnteredPip()) {
+                    fadeExistingPip(true /* show */);
+                }
+            });
+        } else if (!show && !mHasFadeOut) {
             // Fade out the existing PiP to avoid jump cut during seamless rotation.
             fadeExistingPip(false /* show */);
         }

libs/WindowManager/Shell/src/com/android/wm/shell/pip/PipTransitionController.java

@@ -123,6 +123,10 @@ public abstract class PipTransitionController implements Transitions.TransitionH
     public void onFixedRotationStarted() {
     }
 
+    /** Called when the fixed rotation finished. */
+    public void onFixedRotationFinished() {
+    }
+
     public PipTransitionController(
             @NonNull ShellInit shellInit,
             @NonNull ShellTaskOrganizer shellTaskOrganizer,