Add NodeRegion to allow any FlatShadowNode to respond to touch events

Summary: @public When Android dispatches `MotionEvent` to `ReactRootView`, it needs to find a correspoding react node that should receive it. To be able to do it, we need to store boundaries of every `FlatShadowNode` in `FlatViewGroup`. Then we can iterate over node boundaries and find one that contains the touch event coordinates.

Reviewed By: sriramramani

Differential Revision: D2694197

ReactAndroid/src/main/java/com/facebook/react/flat/FlatNativeViewHierarchyManager.java

@@ -56,7 +56,8 @@ import com.facebook.react.uimanager.ViewManagerRegistry;
   /* package */ void updateMountState(
       int reactTag,
       @Nullable DrawCommand[] drawCommands,
-      @Nullable AttachDetachListener[] listeners) {
+      @Nullable AttachDetachListener[] listeners,
+      @Nullable NodeRegion[] nodeRegions) {
     FlatViewGroup view = (FlatViewGroup) resolveView(reactTag);
     if (drawCommands != null) {
       view.mountDrawCommands(drawCommands);
@@ -64,6 +65,9 @@ import com.facebook.react.uimanager.ViewManagerRegistry;
     if (listeners != null) {
       view.mountAttachDetachListeners(listeners);
     }
+    if (nodeRegions != null) {
+      view.mountNodeRegions(nodeRegions);
+    }
   }
 
   /* package */ void updateViewGroup(int reactTag, int[] viewsToAdd, int[] viewsToDetach) {

ReactAndroid/src/main/java/com/facebook/react/flat/FlatShadowNode.java

@@ -25,7 +25,9 @@ import com.facebook.react.uimanager.ViewProps;
 
   private DrawCommand[] mDrawCommands = DrawCommand.EMPTY_ARRAY;
   private AttachDetachListener[] mAttachDetachListeners = AttachDetachListener.EMPTY_ARRAY;
+  private NodeRegion[] mNodeRegions = NodeRegion.EMPTY_ARRAY;
   private FlatShadowNode[] mNativeChildren = FlatShadowNode.EMPTY_ARRAY;
+  private NodeRegion mNodeRegion = NodeRegion.EMPTY;
   private int mNativeParentTag;
   private int mViewLeft;
   private int mViewTop;
@@ -135,6 +137,22 @@ import com.facebook.react.uimanager.ViewProps;
     mNativeParentTag = nativeParentTag;
   }
 
+  /* package */ final NodeRegion[] getNodeRegions() {
+    return mNodeRegions;
+  }
+
+  /* package */ final void setNodeRegions(NodeRegion[] nodeRegion) {
+    mNodeRegions = nodeRegion;
+  }
+
+  /* package */ final NodeRegion getNodeRegion() {
+    return mNodeRegion;
+  }
+
+  /* package */ final void setNodeRegion(NodeRegion nodeRegion) {
+    mNodeRegion = nodeRegion;
+  }
+
   /**
    * Sets boundaries of the View that this node maps to relative to the parent left/top coordinate.
    */

ReactAndroid/src/main/java/com/facebook/react/flat/FlatUIViewOperationQueue.java

@@ -30,14 +30,17 @@ import com.facebook.react.uimanager.UIViewOperationQueue;
     private final int mReactTag;
     private final @Nullable DrawCommand[] mDrawCommands;
     private final @Nullable AttachDetachListener[] mAttachDetachListeners;
+    private final @Nullable NodeRegion[] mNodeRegions;
 
     private UpdateMountState(
         int reactTag,
         @Nullable DrawCommand[] drawCommands,
-        @Nullable AttachDetachListener[] listeners) {
+        @Nullable AttachDetachListener[] listeners,
+        @Nullable NodeRegion[] nodeRegions) {
       mReactTag = reactTag;
       mDrawCommands = drawCommands;
       mAttachDetachListeners = listeners;
+      mNodeRegions = nodeRegions;
     }
 
     @Override
@@ -45,7 +48,8 @@ import com.facebook.react.uimanager.UIViewOperationQueue;
       mNativeViewHierarchyManager.updateMountState(
           mReactTag,
           mDrawCommands,
-          mAttachDetachListeners);
+          mAttachDetachListeners,
+          mNodeRegions);
     }
   }
 
@@ -119,8 +123,9 @@ import com.facebook.react.uimanager.UIViewOperationQueue;
   public void enqueueUpdateMountState(
       int reactTag,
       @Nullable DrawCommand[] drawCommands,
-      @Nullable AttachDetachListener[] listeners) {
+      @Nullable AttachDetachListener[] listeners,
-    enqueueUIOperation(new UpdateMountState(reactTag, drawCommands, listeners));
+      @Nullable NodeRegion[] nodeRegions) {
+    enqueueUIOperation(new UpdateMountState(reactTag, drawCommands, listeners, nodeRegions));
   }
 
   public void enqueueUpdateViewGroup(int reactTag, int[] viewsToAdd, int[] viewsToDetach) {

ReactAndroid/src/main/java/com/facebook/react/flat/FlatViewGroup.java

@@ -19,11 +19,13 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.view.ViewParent;
 
+import com.facebook.react.uimanager.ReactCompoundView;
+
 /**
  * A view that FlatShadowNode hierarchy maps to. Performs drawing by iterating over
  * array of DrawCommands, executing them one by one.
  */
-/* package */ final class FlatViewGroup extends ViewGroup {
+/* package */ final class FlatViewGroup extends ViewGroup implements ReactCompoundView {
   /**
    * Helper class that allows AttachDetachListener to invalidate the hosting View.
    */
@@ -47,6 +49,7 @@ import android.view.ViewParent;
   private @Nullable InvalidateCallback mInvalidateCallback;
   private DrawCommand[] mDrawCommands = DrawCommand.EMPTY_ARRAY;
   private AttachDetachListener[] mAttachDetachListeners = AttachDetachListener.EMPTY_ARRAY;
+  private NodeRegion[] mNodeRegions = NodeRegion.EMPTY_ARRAY;
   private int mDrawChildIndex = 0;
   private boolean mIsAttached = false;
 
@@ -59,6 +62,19 @@ import android.view.ViewParent;
     super.detachAllViewsFromParent();
   }
 
+  @Override
+  public int reactTagForTouch(float touchX, float touchY) {
+    for (NodeRegion nodeRegion : mNodeRegions) {
+      if (nodeRegion.mLeft <= touchX && touchX < nodeRegion.mRight &&
+          nodeRegion.mTop <= touchY && touchY < nodeRegion.mBottom) {
+        return nodeRegion.mTag;
+      }
+    }
+
+    // no children found
+    return getId();
+  }
+
   @Override
   public void dispatchDraw(Canvas canvas) {
     super.dispatchDraw(canvas);
@@ -143,6 +159,10 @@ import android.view.ViewParent;
     mAttachDetachListeners = listeners;
   }
 
+  /* package */ void mountNodeRegions(NodeRegion[] nodeRegions) {
+    mNodeRegions = nodeRegions;
+  }
+
   /* package */ void mountViews(ViewResolver viewResolver, int[] viewsToAdd, int[] viewsToDetach) {
     for (int viewToAdd : viewsToAdd) {
       if (viewToAdd > 0) {

ReactAndroid/src/main/java/com/facebook/react/flat/NodeRegion.java

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.flat;
+
+/* package */ final class NodeRegion {
+  /* package */ static final NodeRegion[] EMPTY_ARRAY = new NodeRegion[0];
+  /* package */ static final NodeRegion EMPTY = new NodeRegion(0, 0, 0, 0, -1);
+
+  /* package */ final float mLeft;
+  /* package */ final float mTop;
+  /* package */ final float mRight;
+  /* package */ final float mBottom;
+  /* package */ final int mTag;
+
+  /* package */ NodeRegion(float left, float top, float right, float bottom, int tag) {
+    mLeft = left;
+    mTop = top;
+    mRight = right;
+    mBottom = bottom;
+    mTag = tag;
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/flat/StateBuilder.java

@@ -31,6 +31,8 @@ import com.facebook.react.uimanager.CatalystStylesDiffMap;
       new ElementsList<>(DrawCommand.EMPTY_ARRAY);
   private final ElementsList<AttachDetachListener> mAttachDetachListeners =
       new ElementsList<>(AttachDetachListener.EMPTY_ARRAY);
+  private final ElementsList<NodeRegion> mNodeRegions =
+      new ElementsList<>(NodeRegion.EMPTY_ARRAY);
   private final ElementsList<FlatShadowNode> mNativeChildren =
       new ElementsList<>(FlatShadowNode.EMPTY_ARRAY);
 
@@ -56,7 +58,10 @@ import com.facebook.react.uimanager.CatalystStylesDiffMap;
 
     float left = node.getLayoutX();
     float top = node.getLayoutY();
-    updateViewBounds(node, tag, left, top, left + width, top + height);
+    float right = left + width;
+    float bottom = top + height;
+    updateNodeRegion(node, tag, left, top, right, bottom);
+    updateViewBounds(node, tag, left, top, right, bottom);
 
     if (mDetachAllChildrenFromViews != null) {
       int[] viewsToDetachAllChildrenFrom = collectViewTags(mViewsToDetachAllChildrenFrom);
@@ -90,6 +95,10 @@ import com.facebook.react.uimanager.CatalystStylesDiffMap;
     node.signalBackingViewIsCreated();
   }
 
+  private void addNodeRegion(NodeRegion nodeRegion) {
+    mNodeRegions.add(nodeRegion);
+  }
+
   private void addNativeChild(FlatShadowNode nativeChild) {
     mNativeChildren.add(nativeChild);
   }
@@ -130,6 +139,7 @@ import com.facebook.react.uimanager.CatalystStylesDiffMap;
       float height) {
     mDrawCommands.start(node.getDrawCommands());
     mAttachDetachListeners.start(node.getAttachDetachListeners());
+    mNodeRegions.start(node.getNodeRegions());
     mNativeChildren.start(node.getNativeChildren());
 
     collectStateRecursively(node, 0, 0, width, height);
@@ -147,11 +157,18 @@ import com.facebook.react.uimanager.CatalystStylesDiffMap;
       node.setAttachDetachListeners(listeners);
     }
 
+    final NodeRegion[] nodeRegions = mNodeRegions.finish();
+    if (nodeRegions != null) {
+      shouldUpdateMountState = true;
+      node.setNodeRegions(nodeRegions);
+    }
+
     if (shouldUpdateMountState) {
       mOperationsQueue.enqueueUpdateMountState(
           tag,
           drawCommands,
-          listeners);
+          listeners,
+          nodeRegions);
     }
 
     final FlatShadowNode[] nativeChildren = mNativeChildren.finish();
@@ -254,6 +271,8 @@ import com.facebook.react.uimanager.CatalystStylesDiffMap;
     float right = left + width;
     float bottom = top + height;
 
+    updateNodeRegion(node, tag, left, top, right, bottom);
+
     if (node.mountsToView()) {
       ensureBackingViewIsCreated(node, tag, null);
 
@@ -264,6 +283,21 @@ import com.facebook.react.uimanager.CatalystStylesDiffMap;
       updateViewBounds(node, tag, left, top, right, bottom);
     } else {
       collectStateRecursively(node, left, top, right, bottom);
+      addNodeRegion(node.getNodeRegion());
+    }
+  }
+
+  private static void updateNodeRegion(
+      FlatShadowNode node,
+      int tag,
+      float left,
+      float top,
+      float right,
+      float bottom) {
+    final NodeRegion nodeRegion = node.getNodeRegion();
+    if (nodeRegion.mLeft != left || nodeRegion.mTop != top ||
+        nodeRegion.mRight != right || nodeRegion.mBottom != bottom) {
+      node.setNodeRegion(new NodeRegion(left, top, right, bottom, tag));
     }
   }