moveTaskToBack also moves ActivityStack to back

Bug: 67931573
Bug: 68952157
Test: manually tested with apps launching chrome. CTS
      ActivityManagerAppConfigurationTests#testTaskMoveToBackOrientation
      now passes again.
Change-Id: Ibe73e1d6accd5fd1f09d193305b1d9697ee19d97

2 files changed, 45 insertions, 2 deletions

diff --git a/services/core/java/com/android/server/am/ActivityStack.java b/services/core/java/com/android/server/am/ActivityStack.java
index 88403fc5dde7..86cac10b10d6 100644
--- a/services/core/java/com/android/server/am/ActivityStack.java
+++ b/services/core/java/com/android/server/am/ActivityStack.java
@@ -870,6 +870,29 @@ class ActivityStack<T extends StackWindowController> extends ConfigurationContai
         }
     }
 
+    /**
+     * @param reason The reason for moving the stack to the back.
+     * @param task If non-null, the task will be moved to the bottom of the stack.
+     **/
+    void moveToBack(String reason, TaskRecord task) {
+        if (!isAttached()) {
+            return;
+        }
+
+        getDisplay().positionChildAtBottom(this);
+        mStackSupervisor.setFocusStackUnchecked(reason, getDisplay().getTopStack());
+        if (task != null) {
+            insertTaskAtBottom(task);
+            return;
+        } else {
+            task = bottomTask();
+            if (task != null) {
+                mWindowContainerController.positionChildAtBottom(
+                        task.getWindowContainerController(), true /* includingParents */);
+            }
+        }
+    }
+
     boolean isFocusable() {
         if (getWindowConfiguration().canReceiveKeys()) {
             return true;
@@ -2581,6 +2604,9 @@ class ActivityStack<T extends StackWindowController> extends ConfigurationContai
         if (position >= mTaskHistory.size()) {
             insertTaskAtTop(task, null);
             return;
+        } else if (position <= 0) {
+            insertTaskAtBottom(task);
+            return;
         }
         position = getAdjustedPositionForTask(task, position, null /* starting */);
         mTaskHistory.remove(task);
@@ -2601,6 +2627,16 @@ class ActivityStack<T extends StackWindowController> extends ConfigurationContai
                 true /* includingParents */);
     }
 
+    private void insertTaskAtBottom(TaskRecord task) {
+        // Unlike insertTaskAtPosition, this will also position parents of the windowcontroller.
+        mTaskHistory.remove(task);
+        final int position = getAdjustedPositionForTask(task, 0, null);
+        mTaskHistory.add(position, task);
+        updateTaskMovement(task, true);
+        mWindowContainerController.positionChildAtBottom(task.getWindowContainerController(),
+                true /* includingParents */);
+    }
+
     final void startActivityLocked(ActivityRecord r, ActivityRecord focusedTopActivity,
             boolean newTask, boolean keepCurTransition, ActivityOptions options) {
         TaskRecord rTask = r.getTask();
@@ -4370,8 +4406,7 @@ class ActivityStack<T extends StackWindowController> extends ConfigurationContai
         updateTaskMovement(tr, false);
 
         mWindowManager.prepareAppTransition(TRANSIT_TASK_TO_BACK, false);
-        mWindowContainerController.positionChildAtBottom(tr.getWindowContainerController(),
-                true /* includingParents */);
+        moveToBack("moveTaskToBackLocked", tr);
 
         if (inPinnedWindowingMode()) {
             mStackSupervisor.removeStack(this);
diff --git a/services/core/java/com/android/server/wm/TaskStack.java b/services/core/java/com/android/server/wm/TaskStack.java
index 6e89e3ea37bb..170feac7b754 100644
--- a/services/core/java/com/android/server/wm/TaskStack.java
+++ b/services/core/java/com/android/server/wm/TaskStack.java
@@ -603,6 +603,14 @@ public class TaskStack extends WindowContainer<Task> implements DimLayer.DimLaye
         } else {
             maxPosition = computeMaxPosition(maxPosition);
         }
+
+        // preserve POSITION_BOTTOM/POSITION_TOP positions if they are still valid.
+        if (targetPosition == POSITION_BOTTOM && minPosition == 0) {
+            return POSITION_BOTTOM;
+        } else if (targetPosition == POSITION_TOP
+                && maxPosition == (addingNew ? stackSize : stackSize - 1)) {
+            return POSITION_TOP;
+        }
         // Reset position based on minimum/maximum possible positions.
         return Math.min(Math.max(targetPosition, minPosition), maxPosition);
     }