Prevent scrolling for handwriting delegator

When stylus movement occurs on a handwriting delegator view, there may
be some latency before the handwriting session starts. During this
latency, the stylus movement should not cause scrolling. This can be
suppressed in the same way that was done for standard handwriting
initiation.

Bug: 228210945
Test: atest android.view.stylus.HandwritingInitiatorTest
Change-Id: Ibafb6031f87fb1b1c1c9e4cfd679eb09b69b8f2a

core/java/android/view/HandwritingInitiator.java

@@ -151,14 +151,16 @@ public class HandwritingInitiator {
                 // Either we've already tried to initiate handwriting, or the ongoing MotionEvent
                 // sequence is considered to be tap, long-click or other gestures.
                 if (!mState.mShouldInitHandwriting || mState.mExceedHandwritingSlop) {
-                    return mState.mHasInitiatedHandwriting;
+                    return mState.mHasInitiatedHandwriting
+                            || mState.mHasPreparedHandwritingDelegation;
                 }
 
                 final long timeElapsed =
                         motionEvent.getEventTime() - mState.mStylusDownTimeInMillis;
                 if (timeElapsed > mHandwritingTimeoutInMillis) {
                     mState.mShouldInitHandwriting = false;
-                    return mState.mHasInitiatedHandwriting;
+                    return mState.mHasInitiatedHandwriting
+                            || mState.mHasPreparedHandwritingDelegation;
                 }
 
                 final int pointerIndex = motionEvent.findPointerIndex(mState.mStylusPointerId);
@@ -183,12 +185,13 @@ public class HandwritingInitiator {
                             mImm.prepareStylusHandwritingDelegation(
                                     candidateView, delegatePackageName);
                             candidateView.getHandwritingDelegatorCallback().run();
+                            mState.mHasPreparedHandwritingDelegation = true;
                         } else {
                             requestFocusWithoutReveal(candidateView);
                         }
                     }
                 }
-                return mState.mHasInitiatedHandwriting;
+                return mState.mHasInitiatedHandwriting || mState.mHasPreparedHandwritingDelegation;
         }
         return false;
     }
@@ -568,6 +571,8 @@ public class HandwritingInitiator {
          * Whether handwriting mode has already been initiated for the current MotionEvent sequence.
          */
         private boolean mHasInitiatedHandwriting;
+
+        private boolean mHasPreparedHandwritingDelegation;
         /**
          * Whether the current ongoing stylus MotionEvent sequence already exceeds the
          * handwriting slop.
@@ -593,6 +598,7 @@ public class HandwritingInitiator {
 
             mShouldInitHandwriting = true;
             mHasInitiatedHandwriting = false;
+            mHasPreparedHandwritingDelegation = false;
             mExceedHandwritingSlop = false;
         }
     }

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

@@ -268,6 +268,41 @@ public class HandwritingInitiatorTest {
         verify(mHandwritingInitiator, times(1)).tryAcceptStylusHandwritingDelegation(delegateView);
     }
 
+    @Test
+    public void onTouchEvent_startHandwriting_delegate_touchEventsHandled() {
+        // There is no delegator view and the delegate callback does nothing so handwriting will not
+        // be started. This is so we can test how touch events are handled before handwriting is
+        // started.
+        mTestView1.setHandwritingDelegatorCallback(() -> {});
+
+        final int x1 = (sHwArea1.left + sHwArea1.right) / 2;
+        final int y = (sHwArea1.top + sHwArea1.bottom) / 2;
+        MotionEvent stylusEvent1 = createStylusEvent(ACTION_DOWN, x1, y, 0);
+        boolean onTouchEventResult1 = mHandwritingInitiator.onTouchEvent(stylusEvent1);
+
+        final int x2 = x1 + mHandwritingSlop / 2;
+        MotionEvent stylusEvent2 = createStylusEvent(ACTION_MOVE, x2, y, 0);
+        boolean onTouchEventResult2 = mHandwritingInitiator.onTouchEvent(stylusEvent2);
+
+        final int x3 = x2 + mHandwritingSlop * 2;
+        MotionEvent stylusEvent3 = createStylusEvent(ACTION_MOVE, x3, y, 0);
+        boolean onTouchEventResult3 = mHandwritingInitiator.onTouchEvent(stylusEvent3);
+
+        final int x4 = x3 + mHandwritingSlop * 2;
+        MotionEvent stylusEvent4 = createStylusEvent(ACTION_MOVE, x4, y, 0);
+        boolean onTouchEventResult4 = mHandwritingInitiator.onTouchEvent(stylusEvent4);
+
+        assertThat(onTouchEventResult1).isFalse();
+        // stylusEvent2 does not trigger delegation since the touch slop distance has not been
+        // exceeded. onTouchEvent should return false so that the event is dispatched to the view
+        // tree.
+        assertThat(onTouchEventResult2).isFalse();
+        // After delegation is triggered by stylusEvent3, onTouchEvent should return true for
+        // ACTION_MOVE events so that the events are not dispatched to the view tree.
+        assertThat(onTouchEventResult3).isTrue();
+        assertThat(onTouchEventResult4).isTrue();
+    }
+
     @Test
     public void onTouchEvent_notStartHandwriting_whenHandwritingNotAvailable() {
         final Rect rect = new Rect(600, 600, 900, 900);