Fix accident evict if drag same app to same position.

We evict all children on current root when start intent to split.
But if drag same app, it will not launch any new task so all task
under root are evicted.

Fix this by doing evict job on startAnimation because we could
get all transition change here. We only evict tasks under split
root if there have new task launched.

Fix: 279873859
Bug: 279063348
Test: manual
Test: pass existing tests
Change-Id: I4793133f060faf628ba85feb5123a2aaf5e0f7fb

libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageCoordinator.java

@@ -482,8 +482,6 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         }
 
         final WindowContainerTransaction wct = new WindowContainerTransaction();
-        final WindowContainerTransaction evictWct = new WindowContainerTransaction();
-        prepareEvictChildTasks(position, evictWct);
 
         options = resolveStartStage(STAGE_TYPE_UNDEFINED, position, options, null /* wct */);
         wct.sendPendingIntent(intent, fillInIntent, options);
@@ -494,12 +492,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         prepareEnterSplitScreen(wct, null /* taskInfo */, position);
 
         mSplitTransitions.startEnterTransition(TRANSIT_TO_FRONT, wct, null, this,
-                null /* consumedCallback */,
-                (finishWct, finishT) -> {
-                    if (!evictWct.isEmpty()) {
-                        finishWct.merge(evictWct, true);
-                    }
-                } /* finishedCallback */, extraTransitType);
+                null /* consumedCallback */, null /* finishedCallback */, extraTransitType);
     }
 
     /** Launches an activity into split by legacy transition. */
@@ -1509,7 +1502,6 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         if (taskInfo != null) {
             wct.startTask(taskInfo.taskId,
                     resolveStartStage(STAGE_TYPE_UNDEFINED, startPosition, null, wct));
-            targetStage.evictAllChildren(wct);
         }
         // If running background, we need to reparent current top visible task to another stage
         // and evict all tasks current under its.
@@ -1519,7 +1511,6 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             updateWindowBounds(mSplitLayout, wct);
             final StageTaskListener anotherStage = targetStage == mMainStage
                     ? mSideStage : mMainStage;
-            anotherStage.evictAllChildren(wct);
             anotherStage.reparentTopTask(wct);
             wct.reorder(mRootTaskInfo.token, true);
             setRootForceTranslucent(false, wct);
@@ -1538,6 +1529,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             mSideStage.addTask(taskInfo, wct);
         }
         mMainStage.activate(wct, true /* includingTopTask */);
+        mSplitLayout.resetDividerPosition();
         updateWindowBounds(mSplitLayout, wct);
         wct.reorder(mRootTaskInfo.token, true);
         setRootForceTranslucent(false, wct);
@@ -1776,7 +1768,10 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         });
     }
 
-    void onChildTaskAppeared(StageListenerImpl stageListener, int taskId) {
+    /** Callback when split roots have child task appeared under it, this is a little different from
+     * #onStageHasChildrenChanged because this would be called every time child task appeared.
+     * NOTICE: This only be called on legacy transition. */
+    private void onChildTaskAppeared(StageListenerImpl stageListener, int taskId) {
         // Handle entering split screen while there is a split pair running in the background.
         if (stageListener == mSideStageListener && !isSplitScreenVisible() && isSplitActive()
                 && mSplitRequest == null) {
@@ -1822,6 +1817,8 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         wct.setForceTranslucent(mRootTaskInfo.token, translucent);
     }
 
+    /** Callback when split roots visiblility changed.
+     * NOTICE: This only be called on legacy transition. */
     private void onStageVisibilityChanged(StageListenerImpl stageListener) {
         // If split didn't active, just ignore this callback because we should already did these
         // on #applyExitSplitScreen.
@@ -1963,6 +1960,8 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         }
     }
 
+    /** Callback when split roots have child or haven't under it.
+     * NOTICE: This only be called on legacy transition. */
     private void onStageHasChildrenChanged(StageListenerImpl stageListener) {
         final boolean hasChildren = stageListener.mHasChildren;
         final boolean isSideStage = stageListener == mSideStageListener;
@@ -2530,7 +2529,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         boolean shouldAnimate = true;
         if (mSplitTransitions.isPendingEnter(transition)) {
             shouldAnimate = startPendingEnterAnimation(
-                    transition, info, startTransaction, finishTransaction);
+                    mSplitTransitions.mPendingEnter, info, startTransaction, finishTransaction);
         } else if (mSplitTransitions.isPendingDismiss(transition)) {
             shouldAnimate = startPendingDismissAnimation(
                     mSplitTransitions.mPendingDismiss, info, startTransaction, finishTransaction);
@@ -2566,7 +2565,8 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         }
     }
 
-    private boolean startPendingEnterAnimation(@NonNull IBinder transition,
+    private boolean startPendingEnterAnimation(
+            @NonNull SplitScreenTransitions.TransitSession enterTransition,
             @NonNull TransitionInfo info, @NonNull SurfaceControl.Transaction t,
             @NonNull SurfaceControl.Transaction finishT) {
         // First, verify that we actually have opened apps in both splits.
@@ -2577,9 +2577,11 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
             final ActivityManager.RunningTaskInfo taskInfo = change.getTaskInfo();
             if (taskInfo == null || !taskInfo.hasParentTask()) continue;
             final @StageType int stageType = getStageType(getStageOfTask(taskInfo));
-            if (stageType == STAGE_TYPE_MAIN) {
+            if (stageType == STAGE_TYPE_MAIN
+                    && (isOpeningType(change.getMode()) || change.getMode() == TRANSIT_CHANGE)) {
+                // Includes TRANSIT_CHANGE to cover reparenting top-most task to split.
                 mainChild = change;
-            } else if (stageType == STAGE_TYPE_SIDE) {
+            } else if (stageType == STAGE_TYPE_SIDE && isOpeningType(change.getMode())) {
                 sideChild = change;
             }
         }
@@ -2598,7 +2600,10 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                 final int dismissTop = mainChild != null ? STAGE_TYPE_MAIN :
                         (sideChild != null ? STAGE_TYPE_SIDE : STAGE_TYPE_UNDEFINED);
                 mSplitTransitions.mPendingEnter.cancel(
-                        (cancelWct, cancelT) -> prepareExitSplitScreen(dismissTop, cancelWct));
+                        (cancelWct, cancelT) -> {
+                            mSideStage.removeAllTasks(cancelWct, dismissTop == STAGE_TYPE_SIDE);
+                            mMainStage.deactivate(cancelWct, dismissTop == STAGE_TYPE_MAIN);
+                        });
                 return true;
             }
         }
@@ -2620,6 +2625,17 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
                     + " before startAnimation().");
         }
 
+        final TransitionInfo.Change finalMainChild = mainChild;
+        final TransitionInfo.Change finalSideChild = sideChild;
+        enterTransition.setFinishedCallback((callbackWct, callbackT) -> {
+            if (finalMainChild != null) {
+                mMainStage.evictOtherChildren(callbackWct, finalMainChild.getTaskInfo().taskId);
+            }
+            if (finalSideChild != null) {
+                mSideStage.evictOtherChildren(callbackWct, finalSideChild.getTaskInfo().taskId);
+            }
+        });
+
         finishEnterSplitScreen(finishT);
         addDividerBarToTransition(info, true /* show */);
         return true;
@@ -2892,6 +2908,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         }
         if (!isSplitScreenVisible()) {
             // If split running background, exit split first.
+            // TODO(b/280392203) : skip doing this on shell transition once this bug is fixed.
             exitSplitScreen(null /* childrenToTop */, EXIT_REASON_RECREATE_SPLIT);
         }
         mLogger.enterRequestedByDrag(position, dragSessionId);
@@ -2903,6 +2920,7 @@ public class StageCoordinator implements SplitLayout.SplitLayoutHandler,
     public void onRequestToSplit(InstanceId sessionId, int enterReason) {
         if (!isSplitScreenVisible()) {
             // If split running background, exit split first.
+            // TODO(b/280392203) : skip doing this on shell transition once this bug is fixed.
             exitSplitScreen(null /* childrenToTop */, EXIT_REASON_RECREATE_SPLIT);
         }
         mLogger.enterRequested(sessionId, enterReason);

libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/splitscreen/StageCoordinatorTests.java

@@ -158,8 +158,6 @@ public class StageCoordinatorTests extends ShellTestCase {
         verify(mStageCoordinator).prepareEnterSplitScreen(eq(wct), eq(task),
                 eq(SPLIT_POSITION_BOTTOM_OR_RIGHT));
         verify(mMainStage).reparentTopTask(eq(wct));
-        verify(mMainStage).evictAllChildren(eq(wct));
-        verify(mSideStage).evictAllChildren(eq(wct));
         verify(mSplitLayout).resetDividerPosition();
         assertEquals(SPLIT_POSITION_BOTTOM_OR_RIGHT, mStageCoordinator.getSideStagePosition());
         assertEquals(SPLIT_POSITION_TOP_OR_LEFT, mStageCoordinator.getMainStagePosition());
@@ -178,7 +176,6 @@ public class StageCoordinatorTests extends ShellTestCase {
         mStageCoordinator.moveToStage(task, SPLIT_POSITION_BOTTOM_OR_RIGHT, wct);
         verify(mStageCoordinator).prepareEnterSplitScreen(eq(wct), eq(task),
                 eq(SPLIT_POSITION_BOTTOM_OR_RIGHT));
-        verify(mMainStage).evictAllChildren(eq(wct));
         assertEquals(SPLIT_POSITION_BOTTOM_OR_RIGHT, mStageCoordinator.getMainStagePosition());
         assertEquals(SPLIT_POSITION_TOP_OR_LEFT, mStageCoordinator.getSideStagePosition());
     }