Add support for context-aware measure and baseline functions

Summary:
@public

Context-aware measure and baseline functions are an internal Yoga feature that will be used for Yoga’s JNI code.

It will be possible to specify a context when calculating layout, which will be passed on to baseline and measure functions. This will be a private feature.

Reviewed By: SidharthGuglani

Differential Revision: D14100509

fbshipit-source-id: acf4a030549b2e38d5ce0cd5dbe837864e5ffd81

tests/YGNodeCallbackTest.cpp

@@ -36,7 +36,36 @@ TEST(YGNode, measure_with_measure_fn) {
       });
 
   ASSERT_EQ(
-      n.measure(23, YGMeasureModeExactly, 24, YGMeasureModeAtMost),
+      n.measure(23, YGMeasureModeExactly, 24, YGMeasureModeAtMost, nullptr),
+      (YGSize{23, 12}));
+}
+
+TEST(YGNode, measure_with_context_measure_fn) {
+  auto n = YGNode{};
+  n.setMeasureFunc(
+      [](YGNode*, float, YGMeasureMode, float, YGMeasureMode, void* ctx) {
+        return *(YGSize*) ctx;
+      });
+
+  auto result = YGSize{123.4, -56.7};
+  ASSERT_EQ(
+      n.measure(0, YGMeasureModeUndefined, 0, YGMeasureModeUndefined, &result),
+      result);
+}
+
+TEST(YGNode, switching_measure_fn_types) {
+  auto n = YGNode{};
+  n.setMeasureFunc(
+      [](YGNode*, float, YGMeasureMode, float, YGMeasureMode, void*) {
+        return YGSize{};
+      });
+  n.setMeasureFunc(
+      [](YGNode*, float w, YGMeasureMode wm, float h, YGMeasureMode hm) {
+        return YGSize{w * wm, h / hm};
+      });
+
+  ASSERT_EQ(
+      n.measure(23, YGMeasureModeExactly, 24, YGMeasureModeAtMost, nullptr),
       (YGSize{23, 12}));
 }
 
@@ -50,6 +79,17 @@ TEST(YGNode, hasMeasureFunc_after_unset) {
   ASSERT_FALSE(n.hasMeasureFunc());
 }
 
+TEST(YGNode, hasMeasureFunc_after_unset_context) {
+  auto n = YGNode{};
+  n.setMeasureFunc(
+      [](YGNode*, float, YGMeasureMode, float, YGMeasureMode, void*) {
+        return YGSize{};
+      });
+
+  n.setMeasureFunc(nullptr);
+  ASSERT_FALSE(n.hasMeasureFunc());
+}
+
 TEST(YGNode, hasBaselineFunc_initial) {
   auto n = YGNode{};
   ASSERT_FALSE(n.hasBaselineFunc());
@@ -65,7 +105,17 @@ TEST(YGNode, baseline_with_baseline_fn) {
   auto n = YGNode{};
   n.setBaseLineFunc([](YGNode*, float w, float h) { return w + h; });
 
-  ASSERT_EQ(n.baseline(1.25f, 2.5f), 3.75f);
+  ASSERT_EQ(n.baseline(1.25f, 2.5f, nullptr), 3.75f);
+}
+
+TEST(YGNode, baseline_with_context_baseline_fn) {
+  auto n = YGNode{};
+  n.setBaseLineFunc([](YGNode*, float w, float h, void* ctx) {
+    return w + h + *(float*) ctx;
+  });
+
+  auto ctx = -10.0f;
+  ASSERT_EQ(n.baseline(1.25f, 2.5f, &ctx), -6.25f);
 }
 
 TEST(YGNode, hasBaselineFunc_after_unset) {
@@ -76,6 +126,21 @@ TEST(YGNode, hasBaselineFunc_after_unset) {
   ASSERT_FALSE(n.hasBaselineFunc());
 }
 
+TEST(YGNode, hasBaselineFunc_after_unset_context) {
+  auto n = YGNode{};
+  n.setBaseLineFunc([](YGNode*, float, float, void*) { return 0.0f; });
+
+  n.setMeasureFunc(nullptr);
+  ASSERT_FALSE(n.hasMeasureFunc());
+}
+
+TEST(YGNode, switching_baseline_fn_types) {
+  auto n = YGNode{};
+  n.setBaseLineFunc([](YGNode*, float, float, void*) { return 0.0f; });
+  n.setBaseLineFunc([](YGNode*, float, float) { return 1.0f; });
+  ASSERT_EQ(n.baseline(1, 2, nullptr), 1.0f);
+}
+
 void PrintTo(const YGSize& size, std::ostream* os) {
   *os << "YGSize{" << size.width << ", " << size.height << "}";
 }

yoga/YGNode.cpp

@@ -101,11 +101,29 @@ YGFloatOptional YGNode::getMarginForAxis(
   return getLeadingMargin(axis, widthSize) + getTrailingMargin(axis, widthSize);
 }
 
+YGSize YGNode::measure(
+    float width,
+    YGMeasureMode widthMode,
+    float height,
+    YGMeasureMode heightMode,
+    void* layoutContext) {
+
+  return measureUsesContext_
+      ? measure_.withContext(
+            this, width, widthMode, height, heightMode, layoutContext)
+      : measure_.noContext(this, width, widthMode, height, heightMode);
+}
+
+float YGNode::baseline(float width, float height, void* layoutContext) {
+  return baselineUsesContext_
+      ? baseline_.withContext(this, width, height, layoutContext)
+      : baseline_.noContext(this, width, height);
+}
+
 // Setters
 
-void YGNode::setMeasureFunc(YGMeasureFunc measureFunc) {
-  if (measureFunc == nullptr) {
-    measure_ = nullptr;
+void YGNode::setMeasureFunc(decltype(YGNode::measure_) measureFunc) {
+  if (measureFunc.noContext == nullptr) {
     // TODO: t18095186 Move nodeType to opt-in function and mark appropriate
     // places in Litho
     nodeType_ = YGNodeTypeDefault;
@@ -115,7 +133,6 @@ void YGNode::setMeasureFunc(YGMeasureFunc measureFunc) {
         children_.size() == 0,
         "Cannot set measure function: Nodes with measure functions cannot have "
         "children.");
-    measure_ = measureFunc;
     // TODO: t18095186 Move nodeType to opt-in function and mark appropriate
     // places in Litho
     setNodeType(YGNodeTypeText);
@@ -124,6 +141,20 @@ void YGNode::setMeasureFunc(YGMeasureFunc measureFunc) {
   measure_ = measureFunc;
 }
 
+void YGNode::setMeasureFunc(YGMeasureFunc measureFunc) {
+  measureUsesContext_ = false;
+  decltype(YGNode::measure_) m;
+  m.noContext = measureFunc;
+  setMeasureFunc(m);
+}
+
+void YGNode::setMeasureFunc(MeasureWithContextFn measureFunc) {
+  measureUsesContext_ = true;
+  decltype(YGNode::measure_) m;
+  m.withContext = measureFunc;
+  setMeasureFunc(m);
+}
+
 void YGNode::replaceChild(YGNodeRef child, uint32_t index) {
   children_[index] = child;
 }
@@ -270,6 +301,8 @@ YGNode& YGNode::operator=(const YGNode& node) {
   print_ = node.getPrintFunc();
   hasNewLayout_ = node.getHasNewLayout();
   nodeType_ = node.getNodeType();
+  measureUsesContext_ = node.measureUsesContext_;
+  baselineUsesContext_ = node.baselineUsesContext_;
   measure_ = node.measure_;
   baseline_ = node.baseline_;
   dirtied_ = node.getDirtied();

yoga/YGNode.h

@@ -12,6 +12,10 @@
 #include "Yoga-internal.h"
 
 struct YGNode {
+  using MeasureWithContextFn =
+      YGSize (*)(YGNode*, float, YGMeasureMode, float, YGMeasureMode, void*);
+  using BaselineWithContextFn = float (*)(YGNode*, float, float, void*);
+
 private:
   void* context_ = nullptr;
   YGPrintFunc print_ = nullptr;
@@ -19,8 +23,16 @@ private:
   bool isReferenceBaseline_ : 1;
   bool isDirty_ : 1;
   YGNodeType nodeType_ : 1;
-  YGMeasureFunc measure_ = nullptr;
-  YGBaselineFunc baseline_ = nullptr;
+  bool measureUsesContext_ : 1;
+  bool baselineUsesContext_ : 1;
+  union {
+    YGMeasureFunc noContext;
+    MeasureWithContextFn withContext;
+  } measure_ = {nullptr};
+  union {
+    YGBaselineFunc noContext;
+    BaselineWithContextFn withContext;
+  } baseline_ = {nullptr};
   YGDirtiedFunc dirtied_ = nullptr;
   YGStyle style_ = {};
   YGLayout layout_ = {};
@@ -35,12 +47,17 @@ private:
       const YGFlexDirection axis,
       const float axisSize) const;
 
+  void setMeasureFunc(decltype(measure_));
+  void setBaseLineFunc(decltype(baseline_));
+
 public:
   YGNode()
-      : hasNewLayout_(true),
-        isReferenceBaseline_(false),
-        isDirty_(false),
-        nodeType_(YGNodeTypeDefault) {}
+      : hasNewLayout_{true},
+        isReferenceBaseline_{false},
+        isDirty_{false},
+        nodeType_{YGNodeTypeDefault},
+        measureUsesContext_{false},
+        baselineUsesContext_{false} {}
   ~YGNode() = default; // cleanup of owner/children relationships in YGNodeFree
   explicit YGNode(const YGConfigRef newConfig) : config_(newConfig){};
   YGNode(const YGNode& node) = default;
@@ -64,24 +81,16 @@ public:
   }
 
   bool hasMeasureFunc() const noexcept {
-    return measure_ != nullptr;
+    return measure_.noContext != nullptr;
   }
 
-  YGSize measure(
-      float width,
-      YGMeasureMode widthMode,
-      float height,
-      YGMeasureMode heightMode) {
-    return measure_(this, width, widthMode, height, heightMode);
-  }
+  YGSize measure(float, YGMeasureMode, float, YGMeasureMode, void*);
 
   bool hasBaselineFunc() const noexcept {
-    return baseline_ != nullptr;
+    return baseline_.noContext != nullptr;
   }
 
-  float baseline(float width, float height) {
-    return baseline_(this, width, height);
-  }
+  float baseline(float width, float height, void* layoutContext);
 
   YGDirtiedFunc getDirtied() const {
     return dirtied_;
@@ -209,9 +218,21 @@ public:
   }
 
   void setMeasureFunc(YGMeasureFunc measureFunc);
+  void setMeasureFunc(MeasureWithContextFn);
+  void setMeasureFunc(std::nullptr_t) {
+    return setMeasureFunc(YGMeasureFunc{nullptr});
+  }
 
   void setBaseLineFunc(YGBaselineFunc baseLineFunc) {
-    baseline_ = baseLineFunc;
+    baselineUsesContext_ = false;
+    baseline_.noContext = baseLineFunc;
+  }
+  void setBaseLineFunc(BaselineWithContextFn baseLineFunc) {
+    baselineUsesContext_ = true;
+    baseline_.withContext = baseLineFunc;
+  }
+  void setBaseLineFunc(std::nullptr_t) {
+    return setBaseLineFunc(YGBaselineFunc{nullptr});
   }
 
   void setDirtiedFunc(YGDirtiedFunc dirtiedFunc) {

yoga/Yoga.cpp

@@ -1080,7 +1080,8 @@ static float YGBaseline(const YGNodeRef node) {
         node,
         &YGNode::baseline,
         node->getLayout().measuredDimensions[YGDimensionWidth],
-        node->getLayout().measuredDimensions[YGDimensionHeight]);
+        node->getLayout().measuredDimensions[YGDimensionHeight],
+        (void*) nullptr);
     YGAssertWithNode(
         node,
         !YGFloatIsUndefined(baseline),
@@ -1697,7 +1698,8 @@ static void YGNodeWithMeasureFuncSetMeasuredDimensions(
         innerWidth,
         widthMeasureMode,
         innerHeight,
-        heightMeasureMode);
+        heightMeasureMode,
+        (void*) nullptr);
 
     node->setLayoutMeasuredDimension(
         YGNodeBoundAxis(