Fix handwriting delegation when delegate already has input connection

Bug: 272520612
Test: atest android.view.stylus.HandwritingInitiatorTest
Change-Id: Ib6dd1d991f93b8309afc8a6ed3dc44fcc35c9f5c

core/java/android/view/HandwritingInitiator.java

@@ -204,6 +204,16 @@ public class HandwritingInitiator {
         mConnectionCount = 0;
     }
 
+    /**
+     * Notify HandwritingInitiator that a delegate view (see {@link View#isHandwritingDelegate})
+     * gained focus.
+     */
+    public void onDelegateViewFocused(@NonNull View view) {
+        if (view == getConnectedView()) {
+            tryAcceptStylusHandwritingDelegation(view);
+        }
+    }
+
     /**
      * Notify HandwritingInitiator that a new InputConnection is created.
      * The caller of this method should guarantee that each onInputConnectionCreated call

core/java/android/view/View.java

@@ -8324,6 +8324,13 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
             onFocusLost();
         } else if (hasWindowFocus()) {
             notifyFocusChangeToImeFocusController(true /* hasFocus */);
+
+            if (mIsHandwritingDelegate) {
+                ViewRootImpl viewRoot = getViewRootImpl();
+                if (viewRoot != null) {
+                    viewRoot.getHandwritingInitiator().onDelegateViewFocused(this);
+                }
+            }
         }
 
         invalidate(true);

core/tests/coretests/src/android/view/stylus/HandwritingInitiatorTest.java

@@ -24,6 +24,7 @@ import static android.view.stylus.HandwritingTestUtil.createView;
 import static com.google.common.truth.Truth.assertThat;
 
 import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
@@ -224,7 +225,7 @@ public class HandwritingInitiatorTest {
     }
 
     @Test
-    public void onTouchEvent_startHandwriting_delegate() {
+    public void onTouchEvent_tryAcceptDelegation_delegatorCallbackCreatesInputConnection() {
         View delegateView = new View(mContext);
         delegateView.setIsHandwritingDelegate(true);
 
@@ -244,6 +245,29 @@ public class HandwritingInitiatorTest {
         verify(mHandwritingInitiator, times(1)).tryAcceptStylusHandwritingDelegation(delegateView);
     }
 
+    @Test
+    public void onTouchEvent_tryAcceptDelegation_delegatorCallbackFocusesDelegate() {
+        View delegateView = new View(mContext);
+        delegateView.setIsHandwritingDelegate(true);
+        mHandwritingInitiator.onInputConnectionCreated(delegateView);
+        reset(mHandwritingInitiator);
+
+        mTestView1.setHandwritingDelegatorCallback(
+                () -> mHandwritingInitiator.onDelegateViewFocused(delegateView));
+
+        final int x1 = (sHwArea1.left + sHwArea1.right) / 2;
+        final int y1 = (sHwArea1.top + sHwArea1.bottom) / 2;
+        MotionEvent stylusEvent1 = createStylusEvent(ACTION_DOWN, x1, y1, 0);
+        mHandwritingInitiator.onTouchEvent(stylusEvent1);
+
+        final int x2 = x1 + mHandwritingSlop * 2;
+        final int y2 = y1;
+        MotionEvent stylusEvent2 = createStylusEvent(ACTION_MOVE, x2, y2, 0);
+        mHandwritingInitiator.onTouchEvent(stylusEvent2);
+
+        verify(mHandwritingInitiator, times(1)).tryAcceptStylusHandwritingDelegation(delegateView);
+    }
+
     @Test
     public void onTouchEvent_notStartHandwriting_whenHandwritingNotAvailable() {
         final Rect rect = new Rect(600, 600, 900, 900);