Fix SingleFlex Child condition

Summary:
Fixes the improper `singleFlexChild` optimization. In the case when all the childs have `flex-grow:0 flex-grow:0` except one child with `flex-grow:1 flex-shrink:1`, then one can simply measure all the non-flexing children and then give the flexing child all the remaining space.

Also added a test case which reproduced the bug

Reviewed By: IanChilds

Differential Revision: D8782684

fbshipit-source-id: ffd4d35b6122f82111b987540efb23bd2a8da5a2

tests/YGFlexTest.cpp

@@ -1,10 +1,10 @@
-/**
- * Copyright (c) 2014-present, Facebook, Inc.
+/*
+ *  Copyright (c) 2014-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
  *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
  */
-
 // @Generated by gentest/gentest.rb from gentest/fixtures/YGFlexTest.html
 
 #include <gtest/gtest.h>
@@ -64,6 +64,90 @@ TEST(YogaTest, flex_basis_flex_grow_column) {
   YGConfigFree(config);
 }
 
+TEST(YogaTest, flex_shrink_flex_grow_row) {
+  const YGConfigRef config = YGConfigNew();
+
+  const YGNodeRef root = YGNodeNewWithConfig(config);
+  YGNodeStyleSetFlexDirection(root, YGFlexDirectionRow);
+  YGNodeStyleSetWidth(root, 500);
+  YGNodeStyleSetHeight(root, 500);
+
+  const YGNodeRef root_child0 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetFlexGrow(root_child0, 0);
+  YGNodeStyleSetFlexShrink(root_child0, 1);
+  YGNodeStyleSetWidth(root_child0, 500);
+  YGNodeStyleSetHeight(root_child0, 100);
+  YGNodeInsertChild(root, root_child0, 0);
+
+  const YGNodeRef root_child1 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetFlexGrow(root_child1, 0);
+  YGNodeStyleSetFlexShrink(root_child1, 1);
+  YGNodeStyleSetWidth(root_child1, 500);
+  YGNodeStyleSetHeight(root_child1, 100);
+  YGNodeInsertChild(root, root_child1, 1);
+  YGNodeCalculateLayout(root, YGUndefined, YGUndefined, YGDirectionLTR);
+
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetLeft(root));
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetTop(root));
+  ASSERT_FLOAT_EQ(500, YGNodeLayoutGetWidth(root));
+  ASSERT_FLOAT_EQ(500, YGNodeLayoutGetHeight(root));
+
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetLeft(root_child0));
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetTop(root_child0));
+  ASSERT_FLOAT_EQ(250, YGNodeLayoutGetWidth(root_child0));
+  ASSERT_FLOAT_EQ(100, YGNodeLayoutGetHeight(root_child0));
+
+  ASSERT_FLOAT_EQ(250, YGNodeLayoutGetLeft(root_child1));
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetTop(root_child1));
+  ASSERT_FLOAT_EQ(250, YGNodeLayoutGetWidth(root_child1));
+  ASSERT_FLOAT_EQ(100, YGNodeLayoutGetHeight(root_child1));
+  YGNodeFreeRecursive(root);
+
+  YGConfigFree(config);
+}
+
+TEST(YogaTest, flex_shrink_flex_grow_child_flex_shrink_other_child) {
+  const YGConfigRef config = YGConfigNew();
+
+  const YGNodeRef root = YGNodeNewWithConfig(config);
+  YGNodeStyleSetFlexDirection(root, YGFlexDirectionRow);
+  YGNodeStyleSetWidth(root, 500);
+  YGNodeStyleSetHeight(root, 500);
+
+  const YGNodeRef root_child0 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetFlexGrow(root_child0, 0);
+  YGNodeStyleSetFlexShrink(root_child0, 1);
+  YGNodeStyleSetWidth(root_child0, 500);
+  YGNodeStyleSetHeight(root_child0, 100);
+  YGNodeInsertChild(root, root_child0, 0);
+
+  const YGNodeRef root_child1 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetFlexGrow(root_child1, 1);
+  YGNodeStyleSetFlexShrink(root_child1, 1);
+  YGNodeStyleSetWidth(root_child1, 500);
+  YGNodeStyleSetHeight(root_child1, 100);
+  YGNodeInsertChild(root, root_child1, 1);
+  YGNodeCalculateLayout(root, YGUndefined, YGUndefined, YGDirectionLTR);
+
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetLeft(root));
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetTop(root));
+  ASSERT_FLOAT_EQ(500, YGNodeLayoutGetWidth(root));
+  ASSERT_FLOAT_EQ(500, YGNodeLayoutGetHeight(root));
+
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetLeft(root_child0));
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetTop(root_child0));
+  ASSERT_FLOAT_EQ(250, YGNodeLayoutGetWidth(root_child0));
+  ASSERT_FLOAT_EQ(100, YGNodeLayoutGetHeight(root_child0));
+
+  ASSERT_FLOAT_EQ(250, YGNodeLayoutGetLeft(root_child1));
+  ASSERT_FLOAT_EQ(0, YGNodeLayoutGetTop(root_child1));
+  ASSERT_FLOAT_EQ(250, YGNodeLayoutGetWidth(root_child1));
+  ASSERT_FLOAT_EQ(100, YGNodeLayoutGetHeight(root_child1));
+  YGNodeFreeRecursive(root);
+
+  YGConfigFree(config);
+}
+
 TEST(YogaTest, flex_basis_flex_grow_row) {
   const YGConfigRef config = YGConfigNew();
 

tests/YGMeasureTest.cpp

@@ -1,10 +1,10 @@
-/**
- * Copyright (c) 2014-present, Facebook, Inc.
+/*
+ *  Copyright (c) 2014-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
  *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
  */
-
 #include <gtest/gtest.h>
 #include <yoga/YGNode.h>
 #include <yoga/Yoga.h>

yoga/Yoga.cpp

@@ -1788,16 +1788,17 @@ static void YGNodeComputeFlexBasisForChildren(
   // child to exactly match the remaining space
   if (measureModeMainDim == YGMeasureModeExactly) {
     for (auto child : children) {
-      if (singleFlexChild != nullptr) {
-        if (child->isNodeFlexible()) {
-          // There is already a flexible child, abort
+      if (child->isNodeFlexible()) {
+        if (singleFlexChild != nullptr ||
+            YGFloatsEqual(child->resolveFlexGrow(), 0.0f) ||
+            YGFloatsEqual(child->resolveFlexShrink(), 0.0f)) {
+          // There is already a flexible child, or this flexible child doesn't
+          // have flexGrow and flexShrink, abort
           singleFlexChild = nullptr;
           break;
+        } else {
+          singleFlexChild = child;
         }
-      } else if (
-          child->resolveFlexGrow() > 0.0f &&
-          child->resolveFlexShrink() > 0.0f) {
-        singleFlexChild = child;
       }
     }
   }