Remove enum count macros

Summary:
@public
Removes all `YG...Count` macros for enums and replaces them with `facebook::yoga::enums::count<YG...>()`.
This removes the need to manually maintain enum counts.

Same as D13597449, working around a defect in clang < 3.9

Reviewed By: amir-shalem

Differential Revision: D13634622

fbshipit-source-id: 344dc70e167b0caf746fe396cedd200f54e52219

Author: davidaurelio

yoga/YGConfig.h

@@ -10,7 +10,8 @@
 #include "Yoga.h"
 
 struct YGConfig {
-  std::array<bool, YGExperimentalFeatureCount> experimentalFeatures = {};
+  std::array<bool, facebook::yoga::enums::count<YGExperimentalFeature>()>
+      experimentalFeatures = {};
   bool useWebDefaults = false;
   bool useLegacyStretchBehaviour = false;
   bool shouldDiffLayoutWithoutLegacyStretchBehaviour = false;

yoga/YGEnums.h

@@ -8,14 +8,52 @@
 
 #include "YGMacros.h"
 
+#ifdef __cplusplus
+namespace facebook {
+namespace yoga {
+namespace enums {
+
+template <typename T>
+constexpr int count(); // can't use `= delete` due to a defect in clang < 3.9
+
+namespace detail {
+template <int... xs>
+constexpr int n() {
+  return sizeof...(xs);
+}
+} // namespace detail
+
+} // namespace enums
+} // namespace yoga
+} // namespace facebook
+#endif
+
 #define YG_ENUM_DECL(NAME, ...)                               \
   typedef YG_ENUM_BEGIN(NAME){__VA_ARGS__} YG_ENUM_END(NAME); \
   WIN_EXPORT const char* NAME##ToString(NAME);
 
+#ifdef __cplusplus
+#define YG_ENUM_SEQ_DECL(NAME, ...)  \
+  YG_ENUM_DECL(NAME, __VA_ARGS__)    \
+  YG_EXTERN_C_END                    \
+  namespace facebook {               \
+  namespace yoga {                   \
+  namespace enums {                  \
+  template <>                        \
+  constexpr int count<NAME>() {      \
+    return detail::n<__VA_ARGS__>(); \
+  }                                  \
+  }                                  \
+  }                                  \
+  }                                  \
+  YG_EXTERN_C_BEGIN
+#else
+#define YG_ENUM_SEQ_DECL YG_ENUM_DECL
+#endif
+
 YG_EXTERN_C_BEGIN
 
-#define YGAlignCount 8
-YG_ENUM_DECL(
+YG_ENUM_SEQ_DECL(
     YGAlign,
     YGAlignAuto,
     YGAlignFlexStart,
@@ -26,17 +64,17 @@ YG_ENUM_DECL(
     YGAlignSpaceBetween,
     YGAlignSpaceAround);
 
-#define YGDimensionCount 2
-YG_ENUM_DECL(YGDimension, YGDimensionWidth, YGDimensionHeight)
+YG_ENUM_SEQ_DECL(YGDimension, YGDimensionWidth, YGDimensionHeight)
 
-#define YGDirectionCount 3
-YG_ENUM_DECL(YGDirection, YGDirectionInherit, YGDirectionLTR, YGDirectionRTL)
+YG_ENUM_SEQ_DECL(
+    YGDirection,
+    YGDirectionInherit,
+    YGDirectionLTR,
+    YGDirectionRTL)
 
-#define YGDisplayCount 2
-YG_ENUM_DECL(YGDisplay, YGDisplayFlex, YGDisplayNone)
+YG_ENUM_SEQ_DECL(YGDisplay, YGDisplayFlex, YGDisplayNone)
 
-#define YGEdgeCount 9
-YG_ENUM_DECL(
+YG_ENUM_SEQ_DECL(
     YGEdge,
     YGEdgeLeft,
     YGEdgeTop,
@@ -48,19 +86,16 @@ YG_ENUM_DECL(
     YGEdgeVertical,
     YGEdgeAll)
 
-#define YGExperimentalFeatureCount 1
-YG_ENUM_DECL(YGExperimentalFeature, YGExperimentalFeatureWebFlexBasis)
+YG_ENUM_SEQ_DECL(YGExperimentalFeature, YGExperimentalFeatureWebFlexBasis)
 
-#define YGFlexDirectionCount 4
-YG_ENUM_DECL(
+YG_ENUM_SEQ_DECL(
     YGFlexDirection,
     YGFlexDirectionColumn,
     YGFlexDirectionColumnReverse,
     YGFlexDirectionRow,
     YGFlexDirectionRowReverse)
 
-#define YGJustifyCount 6
-YG_ENUM_DECL(
+YG_ENUM_SEQ_DECL(
     YGJustify,
     YGJustifyFlexStart,
     YGJustifyCenter,
@@ -69,8 +104,7 @@ YG_ENUM_DECL(
     YGJustifySpaceAround,
     YGJustifySpaceEvenly)
 
-#define YGLogLevelCount 6
-YG_ENUM_DECL(
+YG_ENUM_SEQ_DECL(
     YGLogLevel,
     YGLogLevelError,
     YGLogLevelWarn,
@@ -79,35 +113,38 @@ YG_ENUM_DECL(
     YGLogLevelVerbose,
     YGLogLevelFatal)
 
-#define YGMeasureModeCount 3
-YG_ENUM_DECL(
+YG_ENUM_SEQ_DECL(
     YGMeasureMode,
     YGMeasureModeUndefined,
     YGMeasureModeExactly,
     YGMeasureModeAtMost)
 
-#define YGNodeTypeCount 2
-YG_ENUM_DECL(YGNodeType, YGNodeTypeDefault, YGNodeTypeText)
+YG_ENUM_SEQ_DECL(YGNodeType, YGNodeTypeDefault, YGNodeTypeText)
 
-#define YGOverflowCount 3
-YG_ENUM_DECL(YGOverflow, YGOverflowVisible, YGOverflowHidden, YGOverflowScroll)
+YG_ENUM_SEQ_DECL(
+    YGOverflow,
+    YGOverflowVisible,
+    YGOverflowHidden,
+    YGOverflowScroll)
 
-#define YGPositionTypeCount 2
-YG_ENUM_DECL(YGPositionType, YGPositionTypeRelative, YGPositionTypeAbsolute)
+YG_ENUM_SEQ_DECL(YGPositionType, YGPositionTypeRelative, YGPositionTypeAbsolute)
 
-#define YGPrintOptionsCount 3
 YG_ENUM_DECL(
     YGPrintOptions,
     YGPrintOptionsLayout = 1,
     YGPrintOptionsStyle = 2,
     YGPrintOptionsChildren = 4)
 
-#define YGUnitCount 4
-YG_ENUM_DECL(YGUnit, YGUnitUndefined, YGUnitPoint, YGUnitPercent, YGUnitAuto)
+YG_ENUM_SEQ_DECL(
+    YGUnit,
+    YGUnitUndefined,
+    YGUnitPoint,
+    YGUnitPercent,
+    YGUnitAuto)
 
-#define YGWrapCount 3
-YG_ENUM_DECL(YGWrap, YGWrapNoWrap, YGWrapWrap, YGWrapWrapReverse)
+YG_ENUM_SEQ_DECL(YGWrap, YGWrapNoWrap, YGWrapWrap, YGWrapWrapReverse)
 
 YG_EXTERN_C_END
 
 #undef YG_ENUM_DECL
+#undef YG_ENUM_SEQ_DECL

yoga/YGNode.cpp

@@ -313,7 +313,8 @@ YGValue YGNode::resolveFlexBasisPtr() const {
 }
 
 void YGNode::resolveDimension() {
-  for (uint32_t dim = YGDimensionWidth; dim < YGDimensionCount; dim++) {
+  using namespace yoga;
+  for (int dim = YGDimensionWidth; dim < enums::count<YGDimension>(); dim++) {
     if (!getStyle().maxDimensions[dim].isUndefined() &&
         YGValueEqual(
             getStyle().maxDimensions[dim], style_.minDimensions[dim])) {

yoga/YGNodePrint.cpp

@@ -20,8 +20,7 @@ static void indent(string& base, uint32_t level) {
   }
 }
 
-static bool areFourValuesEqual(
-    const facebook::yoga::detail::Values<YGEdgeCount>& four) {
+static bool areFourValuesEqual(const YGStyle::Edges& four) {
   return YGValueEqual(four[0], four[1]) && YGValueEqual(four[0], four[2]) &&
       YGValueEqual(four[0], four[3]);
 }
@@ -86,7 +85,7 @@ static void appendNumberIfNotZero(
 static void appendEdges(
     string& base,
     const string& key,
-    const facebook::yoga::detail::Values<YGEdgeCount>& edges) {
+    const YGStyle::Edges& edges) {
   if (areFourValuesEqual(edges)) {
     appendNumberIfNotZero(base, key, edges[YGEdgeLeft]);
   } else {
@@ -100,7 +99,7 @@ static void appendEdges(
 static void appendEdgeIfNotUndefined(
     string& base,
     const string& str,
-    const facebook::yoga::detail::Values<YGEdgeCount>& edges,
+    const YGStyle::Edges& edges,
     const YGEdge edge) {
   appendNumberIfNotUndefined(
       base,

yoga/YGStyle.h

@@ -9,6 +9,7 @@
 #include <array>
 #include <initializer_list>
 #include "CompactValue.h"
+#include "YGEnums.h"
 #include "YGFloatOptional.h"
 #include "Yoga-internal.h"
 #include "Yoga.h"
@@ -29,7 +30,8 @@ struct YGStyle {
 
 public:
   using Dimensions = facebook::yoga::detail::Values<2>;
-  using Edges = facebook::yoga::detail::Values<YGEdgeCount>;
+  using Edges =
+      facebook::yoga::detail::Values<facebook::yoga::enums::count<YGEdge>()>;
 
   /* Some platforms don't support enum bitfields,
      so please use BITFIELD_ENUM_SIZED(BITS_COUNT) */

yoga/Yoga-internal.h

@@ -149,6 +149,7 @@ static const float kWebDefaultFlexShrink = 1.0f;
 extern bool YGFloatsEqual(const float a, const float b);
 extern bool YGValueEqual(const YGValue a, const YGValue b);
 extern facebook::yoga::detail::CompactValue YGComputedEdgeValue(
-    const facebook::yoga::detail::Values<YGEdgeCount>& edges,
+    const facebook::yoga::detail::Values<
+        facebook::yoga::enums::count<YGEdge>()>& edges,
     YGEdge edge,
     facebook::yoga::detail::CompactValue defaultValue);

yoga/Yoga.cpp

@@ -105,7 +105,7 @@ bool YGFloatIsUndefined(const float value) {
 }
 
 detail::CompactValue YGComputedEdgeValue(
-    const facebook::yoga::detail::Values<YGEdgeCount>& edges,
+    const YGStyle::Edges& edges,
     YGEdge edge,
     detail::CompactValue defaultValue) {
   if (!edges[edge].isUndefined()) {
@@ -3546,14 +3546,12 @@ static const char* YGSpacer(const unsigned long level) {
 static const char* YGMeasureModeName(
     const YGMeasureMode mode,
     const bool performLayout) {
-  const char* kMeasureModeNames[YGMeasureModeCount] = {
-      "UNDEFINED", "EXACTLY", "AT_MOST"};
-  const char* kLayoutModeNames[YGMeasureModeCount] = {"LAY_UNDEFINED",
-                                                      "LAY_EXACTLY",
-                                                      "LAY_AT_"
-                                                      "MOST"};
-
-  if (mode >= YGMeasureModeCount) {
+  constexpr auto N = enums::count<YGMeasureMode>();
+  const char* kMeasureModeNames[N] = {"UNDEFINED", "EXACTLY", "AT_MOST"};
+  const char* kLayoutModeNames[N] = {
+      "LAY_UNDEFINED", "LAY_EXACTLY", "LAY_AT_MOST"};
+
+  if (mode >= N) {
     return "";
   }