Invalidate layout when node is removed from tree

Summary: The layout of a node is invalid once it leaves the tree. Let's reset it for safety in case it is added to another tree.

Reviewed By: astreet

Differential Revision: D4716022

fbshipit-source-id: 399cc64a4b3f5fd3fc469ea37bdd31abe474dc6c

tests/YGNodeChildTest.cpp

@@ -0,0 +1,36 @@
+/**
+ * Copyright (c) 2014-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.
+ */
+
+#include <gtest/gtest.h>
+#include <yoga/Yoga.h>
+
+TEST(YogaTest, reset_layout_when_child_removed) {
+  const YGNodeRef root = YGNodeNew();
+
+  const YGNodeRef root_child0 = YGNodeNew();
+  YGNodeStyleSetWidth(root_child0, 100);
+  YGNodeStyleSetHeight(root_child0, 100);
+  YGNodeInsertChild(root, root_child0, 0);
+
+  YGNodeCalculateLayout(root, YGUndefined, YGUndefined, YGDirectionLTR);
+
+  ASSERT_EQ(0, YGNodeLayoutGetLeft(root_child0));
+  ASSERT_EQ(0, YGNodeLayoutGetTop(root_child0));
+  ASSERT_EQ(100, YGNodeLayoutGetWidth(root_child0));
+  ASSERT_EQ(100, YGNodeLayoutGetHeight(root_child0));
+
+  YGNodeRemoveChild(root, root_child0);
+
+  ASSERT_EQ(0, YGNodeLayoutGetLeft(root_child0));
+  ASSERT_EQ(0, YGNodeLayoutGetTop(root_child0));
+  ASSERT_TRUE(YGFloatIsUndefined(YGNodeLayoutGetWidth(root_child0)));
+  ASSERT_TRUE(YGFloatIsUndefined(YGNodeLayoutGetHeight(root_child0)));
+
+  YGNodeFreeRecursive(root);
+}

yoga/Yoga.c

@@ -423,6 +423,7 @@ void YGNodeInsertChild(const YGNodeRef node, const YGNodeRef child, const uint32
 
 void YGNodeRemoveChild(const YGNodeRef node, const YGNodeRef child) {
   if (YGNodeListDelete(node->children, child) != NULL) {
+    child->layout = gYGNodeDefaults.layout; // layout is no longer valid
     child->parent = NULL;
     YGNodeMarkDirtyInternal(node);
   }