PointerEvents: Use MotionEvent flags to indicate hoverability

Summary: Changelog: [Internal] Allow for MotionEvents to indicate whether they are dispatched from an input device that supports hoverability

Reviewed By: javache

Differential Revision: D37543296

fbshipit-source-id: 4f70d2bf69ff1c563d8e4a6b5eb6b13b53996b9a

ReactAndroid/src/main/java/com/facebook/react/uimanager/JSPointerDispatcher.java

@@ -72,8 +72,7 @@ public class JSPointerDispatcher {
   }
 
   public void handleMotionEvent(MotionEvent motionEvent, EventDispatcher eventDispatcher) {
-    boolean supportsHover =
-        PointerEventHelper.supportsHover(motionEvent.getToolType(motionEvent.getActionIndex()));
+    boolean supportsHover = PointerEventHelper.supportsHover(motionEvent);
 
     int surfaceId = UIManagerHelper.getSurfaceId(mRootViewGroup);
     int action = motionEvent.getActionMasked();

ReactAndroid/src/main/java/com/facebook/react/uimanager/events/PointerEventHelper.java

@@ -22,6 +22,8 @@ public class PointerEventHelper {
   public static final String POINTER_TYPE_MOUSE = "mouse";
   public static final String POINTER_TYPE_UNKNOWN = "";
 
+  private static final int X_FLAG_SUPPORTS_HOVER = 0x01000000;
+
   public static enum EVENT {
     CANCEL,
     CANCEL_CAPTURE,
@@ -144,7 +146,17 @@ public class PointerEventHelper {
     return EventCategoryDef.UNSPECIFIED;
   }
 
-  public static boolean supportsHover(final int toolType) {
+  public static boolean supportsHover(MotionEvent motionEvent) {
+    // A flag has been set on the MotionEvent to indicate it supports hover
+    // See D36958947 on justifications for this.
+    // TODO(luwe): Leverage previous events to determine if MotionEvent
+    //  is from an input device that supports hover
+    boolean supportsHoverFlag = (motionEvent.getFlags() & X_FLAG_SUPPORTS_HOVER) != 0;
+    if (supportsHoverFlag) {
+      return true;
+    }
+
+    int toolType = motionEvent.getToolType(motionEvent.getActionIndex());
     String pointerType = getW3CPointerType(toolType);
 
     if (pointerType.equals(POINTER_TYPE_MOUSE)) {