Dimming on an embedded TaskFragment vs. parent Task

Migrate the dimmer to TaskFragment and the dim surface
needs to be offset relative to its parent task.

Bug: 202379687
Test: verify dim in two pane
Change-Id: I95fe47ebc66d419b42c1da8cc8216773c295f1d1

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

@@ -473,7 +473,6 @@ class Task extends TaskFragment {
     // to layout without loading all the task snapshots
     final PersistedTaskSnapshotData mLastTaskSnapshotData;
 
-    private Dimmer mDimmer = new Dimmer(this);
     private final Rect mTmpDimBoundsRect = new Rect();
 
     /** @see #setCanAffectSystemUiFlags */

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

@@ -161,6 +161,8 @@ class TaskFragment extends WindowContainer<WindowContainer> {
      */
     int mMinHeight;
 
+    Dimmer mDimmer = new Dimmer(this);
+
     /** This task fragment will be removed when the cleanup of its children are done. */
     private boolean mIsRemovalRequested;
 
@@ -2337,6 +2339,34 @@ class TaskFragment extends WindowContainer<WindowContainer> {
         sendTaskFragmentVanished();
     }
 
+    @Override
+    Dimmer getDimmer() {
+        // If the window is in an embedded TaskFragment, we want to dim at the TaskFragment.
+        if (asTask() == null) {
+            return mDimmer;
+        }
+
+        return super.getDimmer();
+    }
+
+    @Override
+    void prepareSurfaces() {
+        if (asTask() != null) {
+            super.prepareSurfaces();
+            return;
+        }
+
+        mDimmer.resetDimStates();
+        super.prepareSurfaces();
+
+        // Bounds need to be relative, as the dim layer is a child.
+        final Rect dimBounds = getBounds();
+        dimBounds.offsetTo(0 /* newLeft */, 0 /* newTop */);
+        if (mDimmer.updateDims(getPendingTransaction(), dimBounds)) {
+            scheduleAnimation();
+        }
+    }
+
     @Override
     boolean canBeAnimationTarget() {
         return true;