Expose API for using SurfaceControl with ViewRootImpl

This API is appropriately called "ViewRoot". So far we just expose
an API surface to reparent SurfaceControl to the ViewRoot (but without
exposing the ViewRoot's SurfaceControl, to encourage developers not
to shoot themselves in the foot) and to synchronize with the drawing
of the ViewRoot SurfaceControl.

Bug: 173463039
Test: ViewRootSyncTests
Change-Id: I8ce0ed4b3efe50cdb3b71ae0f05ce25438d42368

1 files changed, 18 insertions, 1 deletions

diff --git a/core/java/android/view/ViewRootImpl.java b/core/java/android/view/ViewRootImpl.java
index 426c9504c4f9..c3770f0ef478 100644
--- a/core/java/android/view/ViewRootImpl.java
+++ b/core/java/android/view/ViewRootImpl.java
@@ -224,7 +224,7 @@ import java.util.concurrent.CountDownLatch;
  */
 @SuppressWarnings({"EmptyCatchBlock", "PointlessBooleanExpression"})
 public final class ViewRootImpl implements ViewParent,
-        View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks {
+        View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks, ViewRoot {
     private static final String TAG = "ViewRootImpl";
     private static final boolean DBG = false;
     private static final boolean LOCAL_LOGV = false;
@@ -10249,4 +10249,21 @@ public final class ViewRootImpl implements ViewParent,
             t.apply();
         }
     }
+
+    @Override
+    @Nullable public SurfaceControl.Transaction buildReparentTransaction(
+        @NonNull SurfaceControl child) {
+        if (mSurfaceControl.isValid()) {
+            return new SurfaceControl.Transaction().reparent(child, mSurfaceControl);
+        }
+        return null;
+    }
+
+    @Override
+    public boolean applyTransactionOnDraw(@NonNull SurfaceControl.Transaction t) {
+        registerRtFrameCallback(frame -> {
+            mergeWithNextTransaction(t, frame);
+        });
+        return true;
+    }
 }