Add margin auto support to react native

Summary:
This diff adds margin:auto (https://drafts.csswg.org/css-flexbox-1/#auto-margins) support to React Native. This enables layout not previously supported without inserting empty 'spacer' views. See below Playground for usage.

```
class Playground extends React.Component {
  render() {
    return (
      <View style={{width: '100%', height: '100%', flexDirection: 'row', backgroundColor: 'white'}}>
        <View style={{width: 100, height: 100, backgroundColor: 'red'}}/>
        <View style={{width: 100, height: 100, marginLeft: 'auto', backgroundColor: 'blue'}}/>
      </View>
    );
  }
}
```

Reviewed By: astreet

Differential Revision: D4611753

fbshipit-source-id: e78335565c193f7fb263129a638b444715ba5ab0

React/Base/RCTConvert.m

@@ -507,7 +507,9 @@ RCT_CGSTRUCT_CONVERTER(CGAffineTransform, (@[
     return (YGValue) { [json floatValue], YGUnitPoint };
   } else if ([json isKindOfClass:[NSString class]]) {
     NSString *s = (NSString *) json;
-    if ([s hasSuffix:@"%"]) {
+    if ([s isEqualToString:@"auto"]) {
+      return (YGValue) { YGUndefined, YGUnitAuto };
+    } else if ([s hasSuffix:@"%"]) {
       return (YGValue) { [[s substringToIndex:s.length] floatValue], YGUnitPercent };
     } else {
       RCTLogConvertError(json, @"a YGValue. Did you forget the % or pt suffix?");

React/Views/RCTShadowView.m

@@ -70,19 +70,41 @@ switch (ygvalue.unit) {                          \
     break;                                       \
 }
 
-#define DEFINE_PROCESS_META_PROPS(type)                                                           \
-static void RCTProcessMetaProps##type(const YGValue metaProps[META_PROP_COUNT], YGNodeRef node) { \
-  RCT_SET_YGVALUE(metaProps[META_PROP_LEFT], YGNodeStyleSet##type, node, YGEdgeStart);            \
-  RCT_SET_YGVALUE(metaProps[META_PROP_RIGHT], YGNodeStyleSet##type, node, YGEdgeEnd);             \
-  RCT_SET_YGVALUE(metaProps[META_PROP_TOP], YGNodeStyleSet##type, node, YGEdgeTop);               \
-  RCT_SET_YGVALUE(metaProps[META_PROP_BOTTOM], YGNodeStyleSet##type, node, YGEdgeBottom);         \
-  RCT_SET_YGVALUE(metaProps[META_PROP_HORIZONTAL], YGNodeStyleSet##type, node, YGEdgeHorizontal); \
-  RCT_SET_YGVALUE(metaProps[META_PROP_VERTICAL], YGNodeStyleSet##type, node, YGEdgeVertical);     \
-  RCT_SET_YGVALUE(metaProps[META_PROP_ALL], YGNodeStyleSet##type, node, YGEdgeAll);               \
+#define RCT_SET_YGVALUE_AUTO(ygvalue, setter, ...) \
+switch (ygvalue.unit) {                            \
+  case YGUnitAuto:                                 \
+    setter##Auto(__VA_ARGS__);                     \
+    break;                                         \
+  case YGUnitUndefined:                            \
+    setter(__VA_ARGS__, YGUndefined);              \
+    break;                                         \
+  case YGUnitPoint:                                \
+    setter(__VA_ARGS__, ygvalue.value);            \
+    break;                                         \
+  case YGUnitPercent:                              \
+    setter##Percent(__VA_ARGS__, ygvalue.value);   \
+    break;                                         \
 }
 
-DEFINE_PROCESS_META_PROPS(Padding);
-DEFINE_PROCESS_META_PROPS(Margin);
+static void RCTProcessMetaPropsPadding(const YGValue metaProps[META_PROP_COUNT], YGNodeRef node) {
+  RCT_SET_YGVALUE(metaProps[META_PROP_LEFT], YGNodeStyleSetPadding, node, YGEdgeStart);
+  RCT_SET_YGVALUE(metaProps[META_PROP_RIGHT], YGNodeStyleSetPadding, node, YGEdgeEnd);
+  RCT_SET_YGVALUE(metaProps[META_PROP_TOP], YGNodeStyleSetPadding, node, YGEdgeTop);
+  RCT_SET_YGVALUE(metaProps[META_PROP_BOTTOM], YGNodeStyleSetPadding, node, YGEdgeBottom);
+  RCT_SET_YGVALUE(metaProps[META_PROP_HORIZONTAL], YGNodeStyleSetPadding, node, YGEdgeHorizontal);
+  RCT_SET_YGVALUE(metaProps[META_PROP_VERTICAL], YGNodeStyleSetPadding, node, YGEdgeVertical);
+  RCT_SET_YGVALUE(metaProps[META_PROP_ALL], YGNodeStyleSetPadding, node, YGEdgeAll);
+}
+
+static void RCTProcessMetaPropsMargin(const YGValue metaProps[META_PROP_COUNT], YGNodeRef node) {
+  RCT_SET_YGVALUE_AUTO(metaProps[META_PROP_LEFT], YGNodeStyleSetMargin, node, YGEdgeStart);
+  RCT_SET_YGVALUE_AUTO(metaProps[META_PROP_RIGHT], YGNodeStyleSetMargin, node, YGEdgeEnd);
+  RCT_SET_YGVALUE_AUTO(metaProps[META_PROP_TOP], YGNodeStyleSetMargin, node, YGEdgeTop);
+  RCT_SET_YGVALUE_AUTO(metaProps[META_PROP_BOTTOM], YGNodeStyleSetMargin, node, YGEdgeBottom);
+  RCT_SET_YGVALUE_AUTO(metaProps[META_PROP_HORIZONTAL], YGNodeStyleSetMargin, node, YGEdgeHorizontal);
+  RCT_SET_YGVALUE_AUTO(metaProps[META_PROP_VERTICAL], YGNodeStyleSetMargin, node, YGEdgeVertical);
+  RCT_SET_YGVALUE_AUTO(metaProps[META_PROP_ALL], YGNodeStyleSetMargin, node, YGEdgeAll);
+}
 
 static void RCTProcessMetaPropsBorder(const YGValue metaProps[META_PROP_COUNT], YGNodeRef node) {
   YGNodeStyleSetBorder(node, YGEdgeStart, metaProps[META_PROP_LEFT].value);
@@ -522,9 +544,19 @@ RCT_BORDER_PROPERTY(Bottom, BOTTOM)
 RCT_BORDER_PROPERTY(Right, RIGHT)
 
 // Dimensions
-
 #define RCT_DIMENSION_PROPERTY(setProp, getProp, cssProp)           \
 - (void)set##setProp:(YGValue)value                                 \
+{                                                                   \
+  RCT_SET_YGVALUE_AUTO(value, YGNodeStyleSet##cssProp, _yogaNode);  \
+  [self dirtyText];                                                 \
+}                                                                   \
+- (YGValue)getProp                                                  \
+{                                                                   \
+  return YGNodeStyleGet##cssProp(_yogaNode);                        \
+}
+
+#define RCT_MIN_MAX_DIMENSION_PROPERTY(setProp, getProp, cssProp)   \
+- (void)set##setProp:(YGValue)value                                 \
 {                                                                   \
   RCT_SET_YGVALUE(value, YGNodeStyleSet##cssProp, _yogaNode);       \
   [self dirtyText];                                                 \
@@ -536,10 +568,10 @@ RCT_BORDER_PROPERTY(Right, RIGHT)
 
 RCT_DIMENSION_PROPERTY(Width, width, Width)
 RCT_DIMENSION_PROPERTY(Height, height, Height)
-RCT_DIMENSION_PROPERTY(MinWidth, minWidth, MinWidth)
-RCT_DIMENSION_PROPERTY(MinHeight, minHeight, MinHeight)
-RCT_DIMENSION_PROPERTY(MaxWidth, maxWidth, MaxWidth)
-RCT_DIMENSION_PROPERTY(MaxHeight, maxHeight, MaxHeight)
+RCT_MIN_MAX_DIMENSION_PROPERTY(MinWidth, minWidth, MinWidth)
+RCT_MIN_MAX_DIMENSION_PROPERTY(MinHeight, minHeight, MinHeight)
+RCT_MIN_MAX_DIMENSION_PROPERTY(MaxWidth, maxWidth, MaxWidth)
+RCT_MIN_MAX_DIMENSION_PROPERTY(MaxHeight, maxHeight, MaxHeight)
 
 // Position
 
@@ -644,7 +676,7 @@ static inline YGSize RCTShadowViewMeasure(YGNodeRef node, float width, YGMeasure
 
 - (void)setFlexBasis:(YGValue)value
 {
-  RCT_SET_YGVALUE(value, YGNodeStyleSetFlexBasis, _yogaNode);
+  RCT_SET_YGVALUE_AUTO(value, YGNodeStyleSetFlexBasis, _yogaNode);
 }
 
 - (YGValue)flexBasis

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

@@ -74,6 +74,9 @@ public class LayoutShadowNode extends ReactShadowNode {
       case UNDEFINED:
         setStyleWidth(mTempYogaValue.value);
         break;
+      case AUTO:
+        setStyleWidthAuto();
+        break;
       case PERCENT:
         setStyleWidthPercent(mTempYogaValue.value);
         break;
@@ -134,6 +137,9 @@ public class LayoutShadowNode extends ReactShadowNode {
       case UNDEFINED:
         setStyleHeight(mTempYogaValue.value);
         break;
+      case AUTO:
+        setStyleHeightAuto();
+        break;
       case PERCENT:
         setStyleHeightPercent(mTempYogaValue.value);
         break;
@@ -218,6 +224,9 @@ public class LayoutShadowNode extends ReactShadowNode {
       case UNDEFINED:
         setFlexBasis(mTempYogaValue.value);
         break;
+      case AUTO:
+        setFlexBasisAuto();
+        break;
       case PERCENT:
         setFlexBasisPercent(mTempYogaValue.value);
         break;
@@ -312,6 +321,9 @@ public class LayoutShadowNode extends ReactShadowNode {
       case UNDEFINED:
         setMargin(ViewProps.PADDING_MARGIN_SPACING_TYPES[index], mTempYogaValue.value);
         break;
+      case AUTO:
+        setMarginAuto(ViewProps.PADDING_MARGIN_SPACING_TYPES[index]);
+        break;
       case PERCENT:
         setMarginPercent(ViewProps.PADDING_MARGIN_SPACING_TYPES[index], mTempYogaValue.value);
         break;

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

@@ -554,6 +554,10 @@ public class ReactShadowNode {
     mYogaNode.setWidthPercent(percent);
   }
 
+  public void setStyleWidthAuto() {
+    mYogaNode.setWidthAuto();
+  }
+
   public void setStyleMinWidth(float widthPx) {
     mYogaNode.setMinWidth(widthPx);
   }
@@ -582,6 +586,10 @@ public class ReactShadowNode {
     mYogaNode.setHeightPercent(percent);
   }
 
+  public void setStyleHeightAuto() {
+    mYogaNode.setHeightAuto();
+  }
+
   public void setStyleMinHeight(float widthPx) {
     mYogaNode.setMinHeight(widthPx);
   }
@@ -614,6 +622,10 @@ public class ReactShadowNode {
     mYogaNode.setFlexBasis(flexBasis);
   }
 
+  public void setFlexBasisAuto() {
+    mYogaNode.setFlexBasisAuto();
+  }
+
   public void setFlexBasisPercent(float percent) {
     mYogaNode.setFlexBasisPercent(percent);
   }
@@ -654,6 +666,10 @@ public class ReactShadowNode {
     mYogaNode.setMarginPercent(YogaEdge.fromInt(spacingType), percent);
   }
 
+  public void setMarginAuto(int spacingType) {
+    mYogaNode.setMarginAuto(YogaEdge.fromInt(spacingType));
+  }
+
   public final float getPadding(int spacingType) {
     return mYogaNode.getLayoutPadding(YogaEdge.fromInt(spacingType));
   }