Android: Enable views to be nested within <Text>

Potential breaking change: The signature of ReactShadowNode's onBeforeLayout
method was changed
  - Before: public void onBeforeLayout()
  - After:  public void onBeforeLayout(NativeViewHierarchyOptimizer nativeViewHierarchyOptimizer)

Depends on this css-layout PR:
facebook/yoga#202

Implements same feature as this iOS PR:
facebook#7304

Previously, only Text and Image could be nested within Text. Now, any view can
be nested within Text. One restriction of this feature is that developers must
give inline views a width and a height via the style prop.

Previously, inline Images were supported via
FrescoBasedReactTextInlineImageSpan. To get support for nesting views within
Text, we create one special kind of span per inline view. This span is called
TextInlineViewPlaceholderSpan. It is the same size as the inline view. Its job
is just to occupy space -- it doesn't render any visual. After the text is
rendered, we query the Android Layout object associated with the TextView to
find out where it has positioned each TextInlineViewPlaceholderSpan. We then
position the views to be at those locations.

One tricky aspect of the implementation is that the Text component needs to be
able to render native children (the inline views) but the Android TextView
cannot have children. This is solved by having the native parent of the
ReactTextView also host the inline views. Implementation-wise, this was
accomplished by extending the NativeViewHierarchyOptimizer to handle this case.
The optimizer now handles these cases:
  - Node is not in the native tree. An ancestor must host its children.
  - Node is in the native tree and it can host its own children.
  - (new) Node is in the native tree but it cannot host its own children. An
    ancestor must host both this node and its children.

Limitation: Clipping
====
If Text's height/width is small such that an inline view doesn't completely fit,
the inline view may still be fully visible due to hoisting (the inline view
isn't actually parented to the Text which has the limited size. It is parented
to an ancestor which may have a different clipping rectangle.). Prior to this
change, layout-only views had a similar limitation.

Examples/UIExplorer/js/TextExample.android.js

@@ -390,9 +390,10 @@ var TextExample = React.createClass({
             This text is selectable if you click-and-hold, and will offer the native Android selection menus.
           </Text>
         </UIExplorerBlock>
-        <UIExplorerBlock title="Inline images">
+        <UIExplorerBlock title="Inline views">
           <Text>
-            This text contains an inline image <Image source={require('./flux.png')}/>. Neat, huh?
+            This text contains an inline blue view <View style={{width: 25, height: 25, backgroundColor: 'steelblue'}} /> and
+            an inline image <Image source={require('./flux.png')} style={{width: 30, height: 11, resizeMode: 'cover'}}/>. Neat, huh?
           </Text>
         </UIExplorerBlock>
         <UIExplorerBlock title="Text shadow">

ReactAndroid/src/main/java/com/facebook/csslayout/CSSNode.java

@@ -7,6 +7,11 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  */
 
+// NOTE: this file is auto-copied from https://github.com/facebook/css-layout
+// @generated SignedSource<<da35a9f6c5a59af0d73da3e46ee60a9a>>
+
+// NOTE: Changes in this file must be imported from this css-layout PR: https://github.com/facebook/css-layout/pull/202
+
 package com.facebook.csslayout;
 
 import javax.annotation.Nullable;
@@ -24,7 +29,7 @@
 
 /**
  * A CSS Node. It has a style object you can manipulate at {@link #style}. After calling
- * {@link #calculateLayout()}, {@link #layout} will be filled with the results of the layout.
+ * {@link #calculateLayout(CSSLayoutContext)}, {@link #layout} will be filled with the results of the layout.
  */
 public class CSSNode {
 
@@ -72,6 +77,11 @@ public static interface MeasureFunction {
   private LayoutState mLayoutState = LayoutState.DIRTY;
   private boolean mIsTextNode = false;
 
+  public static final Iterable<CSSNode> NO_CSS_NODES = new ArrayList<CSSNode>(0);
+  public Iterable<CSSNode> getChildrenIterable() {
+    return mChildren == null ? NO_CSS_NODES : mChildren;
+  }
+
   public int getChildCount() {
     return mChildren == null ? 0 : mChildren.size();
   }

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

@@ -0,0 +1,24 @@
+/**
+ * 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.uimanager;
+
+public interface IViewManagerWithChildren {
+  /**
+   * Returns whether this View type needs to handle laying out its own children instead of
+   * deferring to the standard css-layout algorithm.
+   * Returns true for the layout to *not* be automatically invoked. Instead onLayout will be
+   * invoked as normal and it is the View instance's responsibility to properly call layout on its
+   * children.
+   * Returns false for the default behavior of automatically laying out children without going
+   * through the ViewGroup's onLayout method. In that case, onLayout for this View type must *not*
+   * call layout on its children.
+   */
+  public boolean needsCustomLayoutForChildren();
+}

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

@@ -0,0 +1,23 @@
+/**
+ * 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.uimanager;
+
+public enum NativeKind {
+  // Node is in the native hierarchy and the HierarchyOptimizer should assume it can host children
+  // (e.g. because it's a ViewGroup). Note that it's okay if the node doesn't support children. When
+  // the HierarchyOptimizer generates children manipulation commands for that node, the
+  // HierarchyManager will catch this case and throw an exception.
+  PARENT,
+  // Node is in the native hierarchy, it may have children, but it cannot host them itself (e.g.
+  // because it isn't a ViewGroup). Consequently, its children need to be hosted by an ancestor.
+  LEAF,
+  // Node is not in the native hierarchy.
+  NONE
+}

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

@@ -164,16 +164,16 @@ public void updateLayout(
       // Check if the parent of the view has to layout the view, or the child has to lay itself out.
       if (!mRootTags.get(parentTag)) {
         ViewManager parentViewManager = mTagsToViewManagers.get(parentTag);
-        ViewGroupManager parentViewGroupManager;
-        if (parentViewManager instanceof ViewGroupManager) {
-          parentViewGroupManager = (ViewGroupManager) parentViewManager;
+        IViewManagerWithChildren parentViewManagerWithChildren;
+        if (parentViewManager instanceof IViewManagerWithChildren) {
+          parentViewManagerWithChildren = (IViewManagerWithChildren) parentViewManager;
         } else {
           throw new IllegalViewOperationException(
-              "Trying to use view with tag " + tag +
-                  " as a parent, but its Manager doesn't extends ViewGroupManager");
+              "Trying to use view with tag " + parentTag +
+                  " as a parent, but its Manager doesn't implement IViewManagerWithChildren");
         }
-        if (parentViewGroupManager != null
-            && !parentViewGroupManager.needsCustomLayoutForChildren()) {
+        if (parentViewManagerWithChildren != null
+            && !parentViewManagerWithChildren.needsCustomLayoutForChildren()) {
           updateLayout(viewToUpdate, x, y, width, height);
         }
       } else {

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

@@ -68,6 +68,15 @@ private static class NodeIndexPair {
   private final ShadowNodeRegistry mShadowNodeRegistry;
   private final SparseBooleanArray mTagsWithLayoutVisited = new SparseBooleanArray();
 
+  public static void assertNodeSupportedWithoutOptimizer(ReactShadowNode node) {
+    // NativeKind.LEAF nodes require the optimizer. They are not ViewGroups so they cannot host
+    // their native children themselves. Their native children need to be hoisted by the optimizer
+    // to an ancestor which is a ViewGroup.
+    Assertions.assertCondition(
+        node.getNativeKind() != NativeKind.LEAF,
+        "Nodes with NativeKind.LEAF are not supported when the optimizer is disabled");
+  }
+
   public NativeViewHierarchyOptimizer(
       UIViewOperationQueue uiViewOperationQueue,
       ShadowNodeRegistry shadowNodeRegistry) {
@@ -83,6 +92,7 @@ public void handleCreateView(
       ThemedReactContext themedContext,
       @Nullable ReactStylesDiffMap initialProps) {
     if (!ENABLED) {
+      assertNodeSupportedWithoutOptimizer(node);
       int tag = node.getReactTag();
       mUIViewOperationQueue.enqueueCreateView(
           themedContext,
@@ -96,7 +106,7 @@ public void handleCreateView(
         isLayoutOnlyAndCollapsable(initialProps);
     node.setIsLayoutOnly(isLayoutOnly);
 
-    if (!isLayoutOnly) {
+    if (node.getNativeKind() != NativeKind.NONE) {
       mUIViewOperationQueue.enqueueCreateView(
           themedContext,
           node.getReactTag(),
@@ -122,6 +132,7 @@ public void handleUpdateView(
       String className,
       ReactStylesDiffMap props) {
     if (!ENABLED) {
+      assertNodeSupportedWithoutOptimizer(node);
       mUIViewOperationQueue.enqueueUpdateProperties(node.getReactTag(), className, props);
       return;
     }
@@ -151,6 +162,7 @@ public void handleManageChildren(
       ViewAtIndex[] viewsToAdd,
       int[] tagsToDelete) {
     if (!ENABLED) {
+      assertNodeSupportedWithoutOptimizer(nodeToManage);
       mUIViewOperationQueue.enqueueManageChildren(
           nodeToManage.getReactTag(),
           indicesToRemove,
@@ -191,6 +203,7 @@ public void handleSetChildren(
     ReadableArray childrenTags
   ) {
     if (!ENABLED) {
+      assertNodeSupportedWithoutOptimizer(nodeToManage);
       mUIViewOperationQueue.enqueueSetChildren(
         nodeToManage.getReactTag(),
         childrenTags);
@@ -210,8 +223,9 @@ public void handleSetChildren(
    */
   public void handleUpdateLayout(ReactShadowNode node) {
     if (!ENABLED) {
+      assertNodeSupportedWithoutOptimizer(node);
       mUIViewOperationQueue.enqueueUpdateLayout(
-          Assertions.assertNotNull(node.getParent()).getReactTag(),
+          Assertions.assertNotNull(node.getLayoutParent()).getReactTag(),
           node.getReactTag(),
           node.getScreenX(),
           node.getScreenY(),
@@ -223,6 +237,12 @@ public void handleUpdateLayout(ReactShadowNode node) {
     applyLayoutBase(node);
   }
 
+  public void handleForceViewToBeNonLayoutOnly(ReactShadowNode node) {
+    if (node.isLayoutOnly()) {
+      transitionLayoutOnlyViewToNativeView(node, null);
+    }
+  }
+
   /**
    * Processes the shadow hierarchy to dispatch all necessary updateLayout calls to the native
    * hierarchy. Should be called after all updateLayout calls for a batch have been handled.
@@ -231,16 +251,18 @@ public void onBatchComplete() {
     mTagsWithLayoutVisited.clear();
   }
 
-  private NodeIndexPair walkUpUntilNonLayoutOnly(
+  private NodeIndexPair walkUpUntilNativeKindIsParent(
       ReactShadowNode node,
       int indexInNativeChildren) {
-    while (node.isLayoutOnly()) {
+    while (node.getNativeKind() != NativeKind.PARENT) {
       ReactShadowNode parent = node.getParent();
       if (parent == null) {
         return null;
       }
 
-      indexInNativeChildren = indexInNativeChildren + parent.getNativeOffsetForChild(node);
+      indexInNativeChildren = indexInNativeChildren +
+          (node.getNativeKind() == NativeKind.LEAF ? 1 : 0) +
+          parent.getNativeOffsetForChild(node);
       node = parent;
     }
 
@@ -249,8 +271,8 @@ private NodeIndexPair walkUpUntilNonLayoutOnly(
 
   private void addNodeToNode(ReactShadowNode parent, ReactShadowNode child, int index) {
     int indexInNativeChildren = parent.getNativeOffsetForChild(parent.getChildAt(index));
-    if (parent.isLayoutOnly()) {
-      NodeIndexPair result = walkUpUntilNonLayoutOnly(parent, indexInNativeChildren);
+    if (parent.getNativeKind() != NativeKind.PARENT) {
+      NodeIndexPair result = walkUpUntilNativeKindIsParent(parent, indexInNativeChildren);
       if (result == null) {
         // If the parent hasn't been attached to its native parent yet, don't issue commands to the
         // native hierarchy. We'll do that when the parent node actually gets attached somewhere.
@@ -260,20 +282,26 @@ private void addNodeToNode(ReactShadowNode parent, ReactShadowNode child, int in
       indexInNativeChildren = result.index;
     }
 
-    if (!child.isLayoutOnly()) {
-      addNonLayoutNode(parent, child, indexInNativeChildren);
+    if (child.getNativeKind() != NativeKind.NONE) {
+      addNativeChild(parent, child, indexInNativeChildren);
     } else {
-      addLayoutOnlyNode(parent, child, indexInNativeChildren);
+      addNonNativeChild(parent, child, indexInNativeChildren);
     }
   }
 
   /**
-   * For handling node removal from manageChildren. In the case of removing a layout-only node, we
-   * need to instead recursively remove all its children from their native parents.
+   * For handling node removal from manageChildren. In the case of removing a node which isn't
+   * hosting its own children (e.g. layout-only or NativeKind.LEAF), we need to recursively remove
+   * all its children from their native parents.
    */
   private void removeNodeFromParent(ReactShadowNode nodeToRemove, boolean shouldDelete) {
-    ReactShadowNode nativeNodeToRemoveFrom = nodeToRemove.getNativeParent();
+    if (nodeToRemove.getNativeKind() != NativeKind.PARENT) {
+      for (int i = nodeToRemove.getChildCount() - 1; i >= 0; i--) {
+        removeNodeFromParent(nodeToRemove.getChildAt(i), shouldDelete);
+      }
+    }
 
+    ReactShadowNode nativeNodeToRemoveFrom = nodeToRemove.getNativeParent();
     if (nativeNodeToRemoveFrom != null) {
       int index = nativeNodeToRemoveFrom.indexOfNativeChild(nodeToRemove);
       nativeNodeToRemoveFrom.removeNativeChildAt(index);
@@ -283,21 +311,17 @@ private void removeNodeFromParent(ReactShadowNode nodeToRemove, boolean shouldDe
           new int[]{index},
           null,
           shouldDelete ? new int[]{nodeToRemove.getReactTag()} : null);
-    } else {
-      for (int i = nodeToRemove.getChildCount() - 1; i >= 0; i--) {
-        removeNodeFromParent(nodeToRemove.getChildAt(i), shouldDelete);
-      }
     }
   }
 
-  private void addLayoutOnlyNode(
-      ReactShadowNode nonLayoutOnlyNode,
-      ReactShadowNode layoutOnlyNode,
+  private void addNonNativeChild(
+      ReactShadowNode nativeParent,
+      ReactShadowNode nonNativeChild,
       int index) {
-    addGrandchildren(nonLayoutOnlyNode, layoutOnlyNode, index);
+    addGrandchildren(nativeParent, nonNativeChild, index);
   }
 
-  private void addNonLayoutNode(
+  private void addNativeChild(
       ReactShadowNode parent,
       ReactShadowNode child,
       int index) {
@@ -307,30 +331,33 @@ private void addNonLayoutNode(
         null,
         new ViewAtIndex[]{new ViewAtIndex(child.getReactTag(), index)},
         null);
+
+    if (child.getNativeKind() != NativeKind.PARENT) {
+      addGrandchildren(parent, child, index + 1);
+    }
   }
 
   private void addGrandchildren(
       ReactShadowNode nativeParent,
       ReactShadowNode child,
       int index) {
-    Assertions.assertCondition(!nativeParent.isLayoutOnly());
+    Assertions.assertCondition(child.getNativeKind() != NativeKind.PARENT);
 
     // `child` can't hold native children. Add all of `child`'s children to `parent`.
     int currentIndex = index;
     for (int i = 0; i < child.getChildCount(); i++) {
       ReactShadowNode grandchild = child.getChildAt(i);
       Assertions.assertCondition(grandchild.getNativeParent() == null);
 
-      if (grandchild.isLayoutOnly()) {
-        // Adding this child could result in adding multiple native views
-        int grandchildCountBefore = nativeParent.getNativeChildCount();
-        addLayoutOnlyNode(nativeParent, grandchild, currentIndex);
-        int grandchildCountAfter = nativeParent.getNativeChildCount();
-        currentIndex += grandchildCountAfter - grandchildCountBefore;
+      // Adding this child could result in adding multiple native views
+      int grandchildCountBefore = nativeParent.getNativeChildCount();
+      if (grandchild.getNativeKind() == NativeKind.NONE) {
+        addNonNativeChild(nativeParent, grandchild, currentIndex);
       } else {
-        addNonLayoutNode(nativeParent, grandchild, currentIndex);
-        currentIndex++;
+        addNativeChild(nativeParent, grandchild, currentIndex);
       }
+      int grandchildCountAfter = nativeParent.getNativeChildCount();
+      currentIndex += grandchildCountAfter - grandchildCountBefore;
     }
   }
 
@@ -349,7 +376,7 @@ private void applyLayoutBase(ReactShadowNode node) {
     int x = node.getScreenX();
     int y = node.getScreenY();
 
-    while (parent != null && parent.isLayoutOnly()) {
+    while (parent != null && parent.getNativeKind() != NativeKind.PARENT) {
       // TODO(7854667): handle and test proper clipping
       x += Math.round(parent.getLayoutX());
       y += Math.round(parent.getLayoutY());
@@ -361,10 +388,10 @@ private void applyLayoutBase(ReactShadowNode node) {
   }
 
   private void applyLayoutRecursive(ReactShadowNode toUpdate, int x, int y) {
-    if (!toUpdate.isLayoutOnly() && toUpdate.getNativeParent() != null) {
+    if (toUpdate.getNativeKind() != NativeKind.NONE && toUpdate.getNativeParent() != null) {
       int tag = toUpdate.getReactTag();
       mUIViewOperationQueue.enqueueUpdateLayout(
-          toUpdate.getNativeParent().getReactTag(),
+          toUpdate.getLayoutParent().getReactTag(),
           tag,
           x,
           y,